When we started this course, we had made three broad classifications in acoustics. Physical acoustics, which was essentially about how sound propagates in air or in medium in general from point A to point B. Then we had also talked about electro acoustics that was another big category, which concerns itself with transformation of sound into other forms of energy or other forms of energy into sound. Another third big area was psycho acoustics, how the mind, the human brain interprets sound. Then that was the introduction, then we talked in detail about or somewhat in detail about physical acoustics. We went through this plane wave equation, one dimensional equation, one dimensional equation in Cartesian and spherical coordinates, interference of wave, stuff related to physical acoustics. Then we moved into the area of electro acoustics and primarily in area of electro acoustics, what we have talked so far is how is sound generated in engineered systems. In natural systems, sound gets generated. We have not talked about that, but in engineered systems, systems with human brain devices and designs, how is sound generated. So, we have talked about that. Today we will still talk about electro acoustics, but we will focus more on how is sound received or recorded, because that is important to understand from an engineering standpoint for two reasons. If I have the sound of quote and quote of a different of a specific type and we will figure, we will explain what this type means, then what kind of microphones should I use, that understanding has to be there. The second thing is which microphones are good or not so good in a particular application, we have to understand that. So, today we will primarily talk about microphones, we will not talk so much in terms of how microphones can be designed, but how we can intelligently use microphones which meet our needs. So, in that context, we will talk a little bit about the design at a little detail level, but not, we will not go too deep into the detail and then we will also try to map different types of microphones into different types of applications. Microphones essentially measure pressure or in some cases, they measure pressure gradients, in general these are two big broad categories of microphones, pressure microphones and then pressure gradient microphones. And then there is a third category which are hybrid which work on the principle of a combination of both of these, pressure and pressure gradient. So, we will start with pressure microphones, we will start with pressure microphones and within pressure microphones, there are different types or categories of microphones, there could be electro dynamic microphones, there could be condenser or capacitor microphones, there could be piezoelectric microphones, there could be carbon microphones, we will very briefly capture all of these, but let us start understanding how a pressure microphone works. Essentially, what a pressure microphone is, is that I have a casing and then I have a diaphragm which is attached to a suspension system. So, this is my diaphragm, this wiggly line represents the suspension system, so the diaphragm can move in and out. On the back side of the microphone, now this diaphragm is could be metallic or it does not have to be metallic, it is a film, it is a thin film. On the back side, I have a perforated surface, diaphragm and the back perforated surface, they are electrically and then I seal this entire thing. Also, what I have is a small orifice here, which is in green, so I have diaphragm which is member A, I have a perforated screen which is member B, everything into an enclosed cavity and I have a small orifice and my pressure wave when it hits, it gives me a pressure, it hits the diaphragm, so the diaphragm sees some pressure. The front membrane and the back membrane, so what we are talking, this is a particular type of pressure mic, what we are seeing, it is called a condenser mic. The front membrane and the back membrane are connected to a resistance, which is very high in number, very high value of resistor and then I have a battery source, which provides what I call polarizing voltage. The diaphragm and the surface B, they are made up of dielectric material, so they can store charge. Electrical sense, this entire thing looks like, I have a DC supply, a very high value of resistance and then these two flat plates are like capacitors, make a capacitor and what I measure is basically this parameter V 0, which is the voltage across these two plates. Actually, more often I measure the charge Q, so these two plates, they are separated by a distance, some nominal distance, let us say this distance is D. So, my capacitance is C equals area of the surface times permittivity constant over the distance D, now when a pressure wave hits it, hits the diaphragm, the diaphragm moves in or if it is negative pressure, then it moves a little bit out. So, what I am doing is I am sensing changes in this charge Q and then I interpret that change in charge, because my capacitance is changing, my Q is basically C times V 0, when capacitance changes, charge is changing and I sense that change in charge and from that I interpret, try to extract what is the pressure, which the diaphragm is seeing. So, what I have drawn here is basically the electrical component of the circuit, they are also mechanical component of the circuit. You all have now the fundamentals to develop a mechanical component of the circuit, electrical and acoustic component, merge into this thing and you can figure out, when it sees a pressure P, how does Q change, you can figure it out. So, I am not going to go into detail in that aspect, but this is how the pressure microphone works at a very basic level, as you are developing the acoustic component, bear in mind there is a cavity here, so it has some springiness, there is also a mass of the diaphragm, there is also a stiffness of the diaphragm, so all that has to be taken into account, when you develop the entire thing, if you want to. Someone may ask, why do I have this surface B slotted and the essential reason for that is, there could be some frequencies, which may excite the resonance of surface B, so then it does not behave in a very controlled way. So, what the perforations do is, that they act as acoustic resistors, so when you are developing the acoustic sense, you have to include that resistive element and what that resistance does is, it dams out the vibrations. So, this is capacitor mic, this is the capacitor microphone, if my pressure goes up, my charge increases linearly and what we see from this very simple analysis is, that the change in charge does not depend on frequency, there is nothing which relates, which is embedded in the frequency part of, frequency term is not embedded in this ratio, so Q changes regardless, if a pressure wave is hitting at 1000 hertz or a pressure wave is hitting at 50 hertz or pressure wave is hitting at 20000 hertz, if the value of that pressure is same, Q will change by the same amount. So, the response, there is only one caveat, that the size of this device has to be significantly smaller than the wave length of the frequency, wave length of the perturbation. If I plot P d, P d is basically the pressure difference outside and pressure difference inside, inside it is atmospheric pressure, because I have this small orifice, because when you move microphone from location A to location B, you can take it in aircraft, pressure can change. So, I have that small orifice to make sure that, the ambient pressure is same as whatever is the ambient pressure outside, that is the purpose. So, P d is basically P outside minus P inside, which is basically P. So, if I plot P d versus log of omega, as long as my lambda, my size of the object which I can represent by this dimension A is significantly small than lambda over 2 pi, then my response curve is a flat curve. So, a device of this type gives me a fairly straight response curve over, I can make this range as much as I want by just basically shrinking the size of the microphone to whatever value I like. So, this gives a very linear response over an extended frequency, but because I have to have this charging battery in it, this is an expensive device. This is I have to provide a polarization voltage and make that happen that requires lot of money. So, this makes things very expensive. Also the tolerance is required in construction of this kind of equipment are very tight. This particular type of a pressure microphone is expensive to make, the expensive. So, this is one type of a pressure microphone, which is called a capacitor microphone. You said that the charge relation, charge does not depend on the frequency, but the way it changes does depend on the frequency. What do you mean? Because charge is dependent on the capacitance and the capacitance is dependent on the effective distance, which will change with the vibrations. It will change with the vibration and what is it? If I am putting a pressure regardless of whatever frequency it is, let us say it has a value of 5 newtons per meter square, then my member will just move in accordingly by the same amount. It is a pressure wave. So, accordingly it will vibrate and because of that the effective distance between the two membranes will change with the frequency same as that the pressure wave is getting the entire thing. Rate of change of charge will depend on frequency. Rate of change of charge will depend on frequency, but not the charge. I am just asking. But that is why we are measuring charge. So, we are not measuring current, we are measuring the charge, which is an integrated quantity. So, that will not depend on frequency. And sir, the perforation is that you talk about the same thing can happen with a diaphragm also. So, they engineer diaphragm in such a way. You cannot make the diaphragm also perforated. So, you have to engineer diaphragm in such a way that now as you keep on shrinking the size of the diaphragm to make things smaller to meet the frequency, it also automatically starts between more and more stiff. But yes, engineering diaphragms if you want to measure up to 20000 hertz, the full band or audio band, then engineering it is not easy. It is a very difficult thing. But in theory, you can make things as small as possible and that will give you a leader response. Inherently in the mechanics of the system, there is nothing which says that the response will be not straight as frequency change. So, in a very broad sense, this is a pressure microphone, because what we are measuring is changes in pressure. The second big category is pressure gradient microphones. These microphones are also called by some people as velocity microphones and we will see that a little later why they are called velocity microphones. In general, the way these mics work is that you have again a tube. So, you have a diaphragm and you have this kind of a tube which is not long. Now, my pressure wave is coming from this side. Let us say this is called P 1. This pressure and this has fairly wide slots. So, unlike a small orifice for equalization of pressure, what you have here is a fairly wide gap which can enter into this tube or a cavity. So, the pressure can sound also travels like this and let us say this length is delta L. The length L, so let us say this pressure on the inside which when it hits the diaphragm is P 2. Sound travels delta L distance more for pressure P 2, because it has to go inside and hit it. So, there is a change in pressure associated with some delta L. So, essentially what we are measuring here is the pressure gradient. So, P D which is the difference in pressure is mathematically we can say gradient of P times delta L. It is a dot product of these two vectors, where P 1 is pressure outside the tube near the diaphragm, P 2 is pressure inside the tube near the diaphragm, delta L is the distance difference in distance traveled by the two waves and it is a dot product, because when you have a gradient it is a vector and it has some directionality associated with it. So, this delta L has to be aligned with that gradient. So, this is essentially del P over del x for instance, if I am only in thinking about x direction times delta L which is a scalar times cosine of theta. So, this delta L is the entire distance from outside to the yes, but we have to take it is dot product. So, in this case if the direction of P 1 is same as this length of this length, then basically literally the delta L will be this length plus this length. So, now what we will do is let us look at a scenario when this whole device is at an angle from P 1 and let us see what it does to us. In this case which is case A, theta is 0, but what we will look at it is another scenario. So, case B, theta is not equal to 0, I will have to make a rather long big drawing just so that things are visible. I have to make a gap that is my P 1, my delta L is associated with this path, this angle is theta, my pressure difference is minus gradient of P times delta L times cosine of theta. Why did I have negative gradient of P? Because I mean if I look at it physically, if P 2 is larger then listen I have to define a coordinate system, this is my coordinate. So, going forward is positive x, if P 2 is larger than P 1 then the displacement in the membrane will be negative x direction. So, for positive gradient P I have negative x, so that is why I have a negative delta P. So, P D is minus delta P times delta L times cosine of theta, again the standard things that the size this dimension A has to be small compared to the wavelengths we are going to measure all that has to be clear. For theta equals 0, P D is maximum for theta equals 90 degrees, P D is minimum which is 0. So, in this kind of a contraption I am measuring the movement of the membrane which is basically a consequence of the difference in pressures attributed to a delta L. So, that is why it is called a pressure gradient microphone. P, we know x omega is P plus E minus j omega x over c, I am assuming in this particular relation that I have a forward traveling planar wave, there is nothing no reflection happening, so there is no P negative term. So, gradient of P is minus P plus omega j over c E minus j omega x over c.  So, I will just rewrite this relation P D equals P plus omega j over c E minus j omega x over c times cosine of theta times delta L. So, if there is no reflection then basically P 1 is same as P plus right, if I am trying to plot P D and I do a boat plot. So, I have a log omega here I am plotting decibels for P D, how will the curve look like for a given value of x the question is see at this point x is defined wherever my wave is hitting the microphone x is defined x is not changing theta is not changing for a given value of x and theta. If I change the frequency how does P D change, what will be the curve look like it will be a flat line or positive slope negative slope what will it be? Why will it be? It will be positive slope omega, there is nothing positive negative here, it will be something like this and this will be some I think it will be 20 degree. So, that is my transfer function. So, clearly this is not a, so for different frequencies if I am measuring P D for the same amount of P D same magnitude of P D, if I measure it at 100 hertz the signal measured in terms of voltage when the membrane moves will be 1, if I measure it at 1000 hertz which is a decade apart the signal measured will be 20 decibels less right because of this relation. So, I do not like this and that is coming essentially because of this omega j over c term how do I get rid of this term, what I can do is I can integrate this guy. So, omega j over c goes away, so I can multiply this by 1 over j omega, so the omega term goes away or in electrical terms they use this word called integrator. So, my input is P D and whatever voltage I am getting is after integrating it, so I get rid of this. So, once I integrate it my response curve, my response curve becomes how will be the response curve look like that omega term goes away. So, what will happen, it will become a flat straight line right shall I introduce you and get it. Sir, but there is x e minus j omega x by c, x is fixed all what I am plotting is the transfer function of P D with I am plotting a transfer function of P D with respect to the incident wave. So, this e minus j x term gets eliminated, so I get a flat straight line. This will be P not P D, you can call it I am being a little sloppy yes, this is voltage. So, I get a flat straight line, so this is how pressure gradient microphones they are also called pressure gradients they are also called velocity microphones because we know that from Newton's law, I think this is the relation. So, they are also measuring basically velocity, especially after you have done the integration in the velocity, that is why they are called velocity microphones, but in the truest sense they measure pressure gradient. This is the response for a plane wave and once I integrate it, this is the response for a plane wave of a pressure gradient one, but in real application suppose I am speaking and it goes to you it may not be a plane wave you may be you do not know whether it is a plane wave or it is a spherical wave. So, let us also see how it responds this kind of a contraption how it works for a spherical wave. So, for a spherical wave the wave front forward going without any reflections wave front is P plus over r e minus j omega r over c and let us say my wave front is such these are spherical waves in this direction and the orientation of the diaphragm is like this, this is my diaphragm.   So, I will just rewrite this because I am going to do a boat plot here is P r omega cosine theta 1 over r plus j omega over c delta l. If I plot in decibels because of this particular term how will my boat plot look like this is log omega this is decibels for P d. A boat plot has a low frequency asymptote and high frequency asymptote what is the low frequency asymptote going to be flat line will be flat line and the high frequency asymptote will have a positive slope of 20 degree. And the actual curve will look something like the crossover point will be such that this is log omega naught where omega naught is equal to r c over omega naught equals to the wherever I am placing the microphone. And how far it is from the spherical source that here I have still not integrated now either in a hardware either you integrate it or you do not integrate it. So, in case of plane waves I had decided to integrate it because this is a flat response. So, let us see what it does in this case. So, once I integrate it basically my actual response curves looks like this basically the way you get it is you divide this whole bracketed term by omega j omega. So, this is again my decibels log omega this break point which is going to be somewhere here is going to correspond to omega naught above a certain point it starts between flat I mean this is going to be an asymptote. So, I should be more careful something like it becomes fairly flat, but at low frequencies you see a spike. The other thing we have not talked about is that there is a cosine theta term in both the spherical and as well as the plane wave expressions. What that means is that if my microphone is placed in the direction of the incident wave it will see maximum amplitude if it is placed at 90 degrees it will see 0 value. So, I draw polar plot and on a linear scale the curve looks like this these are supposed to be equal circles if this is a bad drawing, but this is supposed to be equal circles. So, this is 0 degrees the rate of the radius represents the magnitude I do not want to confuse with this length represents the magnitude. So, at 0 degrees the microphone will be very sensitive to incident pressure waves at 90 degrees it will have it will not record anything and at minus at 180 degrees it will again start recording at maximum level. So, the response here is bidirectional that is the first thing. Other thing is that in most of the cases you had unless you are really really far away from radiating you know single source in most of the unless you are really very far from you know point sources. Suppose I am speaking unless you are really far away from me this point source acts as a spherical source we have talked about it earlier. So, in most of the cases a microphone measures sounds emanating for point sources with act as radially propagating sources and what that means is that if I place this microphone very close to the source what will be the measurement it will faithfully record high frequency data because the response curve is flat in this zone, but it will record low frequency information at a higher decibel level. Now, when I play the same sound track in reality suppose I am speaking my low frequency sound or you know information gets recorded at a higher decibel level high frequency get record gets recorded at quote unquote normal level when I play the same sound track again I will sound like a person who has more bass this is a trick a lot of singers use that if they want to have a lot of their heavy voice they use this they use these kind of microphones and place microphone very close to there now you may have seen it like that. So, it is a base enhancing technique also a lot of discussions when you hear on radio you will see that we will feel that the person who is speaking he has a very heavy voice it is because of this artifact. So, this is the polar plot in absolute terms and if I plot the same thing in decibel terms the polar plot looks a little steeper it looks like a butterfly because the shape of these pictures is like a figure of eight these microphones are also called figure eight microphones there is some general. So, we have talked about microphones which measure pressure microphones which measure pressure gradients now there is a third category which rely on both. So, these are called some guys call it pressure gradient microphones type two, but that is not a very popular term, but it is pressure and pressure gradient microphones. So, the construction looks something like this again I have a diaphragm. So, I have a suspension system suspension stiffness here in these two wiggly things is a fairly rigid diaphragm and then there is a cavity of volume V naught which is filled with regular air and on the other side I have a perforated screen which offers an acoustic resistance R e my pressure wave is here in the pressure p 1 and the same pressure wave hits on the other side at the level p 2 and that length is delta l. So, I can construct a simple four point network for this for just the electrical acoustic portion of this thing. So, this is called Z A T I will explain what these terms mean this is C A this is R A pressure. So, Z A D is the overall impedance offered by the diaphragm C A is associated with the compliance of this cavity of volume V naught R A we have already defined its acoustic resistance p 1 is in pressure outside the diaphragm p 2 is pressure just outside the screen and this is what kind of model is this impedance model or mobility model because my pressure is the across variable. So, let us say my volume velocity which the diaphragm is seen is V V D and volume velocity which the screen is seen is V V naught two relations here V V D I am basically considering this loop loop 1 and then there is another loop loop 2. So, my p 1 is V V D times Z A D plus V V D times 1 over C A minus V V O times C A right. So, I will write that relation V V D times Z A D plus 1 over S C A minus V V naught times 1 over S C A minus V V naught equals P 1 S is my complex J omega and similarly for the second loop my relation is V V naught V V D times 1 over S C A plus V V naught acoustic resistance plus 1 over S C A equals minus V 2. So, let us say this is my relation 1. So, if I know p 1 and p 2 then I can figure out V V D and V V naught I know everything else in these two relations. So, what I will do is in next equation set of equations I will try to compute what is p 1 and p 2. So, p 1 is my incident wave p 0 e minus j omega x over C I am assuming again flat one dimensional wave without any reflections and p 2 equals p 1 plus del over del x plus del over del del theta p naught e minus j omega x over C times del L cosine theta. So, this becomes p 1 1 minus j omega over C del L cosine theta. So, now I know p 1 and I know p 2 I can plug these in one this is equation two. So, if I do so I can from two I can figure out what is V D and V V naught and I also know that p D equals p 2 minus p 1 pressure difference between the two sides of the system and so this is there. So, if I do mathematics with all these three equations at the end of the day I mean this is just regular math I can find the ratio E D over E 1 is this is a long term Z A D times R A plus del L cosine theta over velocity of sound times acoustic compliance.  So, you can play with these three relations to get E D over p 1 and you end up getting this. Now, just to make things look a little simple I define a quantity B such that B is delta L over R A times C times C A.  So, in case of a pressure differential mic we had just cosine theta in the term here we have 1 plus some constant times cosine theta. So, pressure differential mic was bi-directional just because of cosine theta terms. Here I have the flexibility to play with B B is basically delta L R A I cannot change C velocity of sound, but I can change all other parameters delta L R A and C A and depending on how I change it I can change the directional pattern of this pressure pressure and pressure this combination mic in whatever way I want it to be within the ream of feasibility. Let us assume that let us say that B is 1 we can assume we can construct a mic with specific parameters such that B comes to 1. So, in that case my polar pattern looks something like this. Someday I have to take a class in drawing this is called a cardoid shape. So, you get different form factors for this cardoid shape based on how you play with B essentially what this shows is that if I have mic pointing towards you it will sense your sound and if I am opposite you behind the mic it will not sense my sound. So, this is also directional mic, but I can change the shape of this by playing with B in different I mean to a certain extent. So, we have seen a pressure mic how it operates and what kind of features it has then we have seen pressure gradient mic and then combination of pressure and pressure gradient mic. I forgot to mention one thing that why is this called a combination mic or a pressure plus pressure gradient mic and the reason for that is that in the process when we are developing this entire relation somewhere in the middle we will come across a term we will come across a term where P d will be something a longish expression Z A d P 1 R j plus P 1 minus P 2 over j omega C a basically if you the way you get this is if you solve for V and V naught and then find P d from there you get this relation and what this shows is that pressure differential is a function of depends on P 1 minus P 2 and it also depends on P 1 that is why it is combination. So, from a mathematical standpoint this is what I wanted to cover today. So, now in next 25, 20, 25 minutes what we will do is we will just in a subjective sense we will go over we now understand at a basic level how different types of mics work, how based on their designs they can be directional in specific directions. So, based on that what we will do is we will discuss different type of microphones and how they are relevant for specific application. We have pressure mics and there are 3, 4 broad categories one is electrodynamic mic and electrodynamic. So, in pressure mic there are several categories first one is electrodynamic think about this if you have a transducer a speaker which we discussed in last several lecture instead of exciting it with a voltage if I do not excited with a voltage, but I just so sound energy at it. So, pressure ways hit the diaphragm what will happen the diaphragm is going to move and that will induce current in the voice coil that is how an electrodynamic mic works it is basically an inverted acoustic some people also call it moving coil microphone because the coil is moving and electrodynamic mic can have one membrane, but a membrane if it is this large it will have its own modes which will be which can be below a certain threshold. So, some mics some more fancy mics of electrodynamic category they have several membranes to get an extended frequency response for the system. So, this itself can be single membrane and then multi membrane is a fairly commonly used mic because it is a pressure mic is it omnidirectional or is it bidirectional or in one direction it is it is an omnidirectional senses pressure does not matter how the mic is oriented it will just sense the pressure at that point it is not sensing pressure differential. Sir, but it has a cost atom it is it has a cost atom in certain theta it will not sense, but other way it will sense. In theoretical from purely theoretical standpoint it should not have sensitivity to direction see you have a microphone like this and all it is sensing is pressure acting on this membrane. So, if I pressure acts in all directions at a point right pressure acts on all directions pressure gradients are direction specific if I make it like this pressure is still acting inside. The electrodynamic mics are fairly omnidirectional so if you place only omnidirectional mic and there is a crowd they can does not matter where the person is sitting if you have round table discussion you put a microphone in center people all around it their sounds would be picked up by the microphone. Also by nature of their construction these microphones are resistant to moisture which is an important thing. So, and they are fairly inexpensive to make. So, they are very widely used the second one is capacitor mic capacitor condenser we discussed this earlier today right where we are actually measuring the charge on the capacitor. Now, within this there are two types polarizing and non polarizing or others also call it electorate. So, in polarizing we have seen in the earlier part of today's lecture you have to put an external battery to provide an initial charge polarizing charge across the two capacitive plates that makes things very expensive. The polarizing type of mics are fairly very accurate and also they have a very flat frequency response because when we when we did a very basic analysis we saw that the relationship between pressure and omega is of a flat line right. By the way electrodynamics might may not have a flat frequency response as flat as capacitor slash condenser mic because as we saw the response of a regular speaker it is not flat it has different bands. So, electrodynamic mics behave in terms of frequency response similar to speakers we were on polarizing mics. Now electorate mics they do not have a charge provided by an external battery source rather what they have is that the two parallel plates are essentially made of dielectric materials and they have charge deposited on them to begin with. How do they do it? What they do is that when the thing is being made you take a dielectric material and then it is heated up when things are in heated state above a certain threshold the polarizing polar molecules in that dielectric materials they can move back and forth. So, they heat it the polar molecules have a propensity or freedom to move and orient themselves and in such a state they apply the manufacturing process such that an external electrostatic field is applied. So, you have a positive and negative and electrostatic field is passing through between the field you place this material which is made of dielectric material in a heated state. So, these polar molecules orient themselves accordingly in that state then the thing is cooled. So, then the molecules do not revert back to whatever other orientation. So, then you have a permanent charge built up on both the plates you have a positive charge and negative charge built up on both the plates. So, that makes things less expensive. So, because of this electric my probably today are the most popular microphones in the world. So, they are really cheap and this can be mass produced because basically a lot of these films are like pieces of plastic, cheap plastic and they deposit charge on them through this process. A drawback of these is that over a period of time this charge starts dissipated because of heat. But again these are also have these also by from a theoretical standpoint they have a fairly flat frequency response. If you make them small enough you can enhance the frequency spectrum the microphone to as much as you want. They are very reliable they are still not as good as the polarizing type of microphones and it is not that you cannot make these microphones as good as the polarizing microphones.  So, once you make things in very large volumes the quality or the fidelity of an instrument goes down. If you make one piece at a time and pay a lot of attention to every single piece you will do a better job. So, because of that reason because they are mass produced in general they do not have as high a quality as the polarizing microphones. But again they are only directional and these guys are used in a lot of applications. There is a microphone here sitting here in this tablet in your cell phones you have an electric most likely you have an electric my computers almost all places where you have you need very small microphones these things are sitting here. So, that is condenser the third one is piezoelectric again this is also a pressure my but what it does is it senses pressure by due to when pressure gets exerted the crystal generates a voltage that voltage is sent. So, that is the third category the fourth one is carbon resistance these are kind of but earlier especially in on in a lot of analog telephones you would have these mics and the way they operate is there is a small button in the device which is packed with carbon granules as the pressure wave hits a surface of this it presses. So, the resistance of the carbon granule changes accordingly in some predefined way that is resistance changes sense by the electronics and that gets recorded or converted. So, it was used a lot in old type of type of telephones really those black telephones you may still see some and also in recording industry. So, this is these are four major types of pressure microphones electro dynamic capacitor piezoelectric and carbon let us look at pressure gradient mics these are directional we have seen through the mathematics specifically they are bi-directional. So, at 0 degrees and 180 degrees they have maximum response at 90 degrees the response is virtually 0 given that if you have a public address system and the requirement is that the microphone should be able to pick up the voice of let us say the speaker and the voice of the crowd which is on front side people tend to use these type of microphone. So, it depends on the nature of the requirement while these microphones are used you have to pay more attention to the frequency spectrum you have to pay attention even in pressure mics I mean what is the frequency band, but here we saw that the frequency spectrum is booming at low frequencies and flat at high frequencies. So, one has to be careful as I mentioned earlier lot of singers also use it for the special feature that these microphones tend to produce more boomy sound at low frequency. And then the third category we talked about is pressure and gradient mics combo. So, again here you have the advantage of directionality and these mics as well as pressure gradient mics again both these are very frequently used in broadcasting system because of the directionality feature. In auditoriums suppose you have play happening on the stage or you have a bunch of singers you do not want this noise or the sound of the audience to get picked up by the microphone. So, you will use a combination of some of these.


I used to be a teacher full-time and now I make TikToks, do podcasts and teach other people how to make videos for a living. This is my little studio here and you can see the full setup on my YouTube channel, The Sevo Show. You can actually watch the episodes of where we record it, right? This is my whiteboard with all the stuff. This is an extra chair when we put an extra guest in here. This is where the producer sits. Notice that there's some switch cables and computers and stuff. This is the PC station for the people that come in and want to help me then only use PC, it's not Apple. And this is the Apple station for all the people that want to edit properly and use an iMac. Good thanks. Here's some of my lenses, some of my audio gear, some other random stuff like lighting, bags with flash photography and stuff. This is my main lighting source for the podcast. Been doing it for almost eight years. I'm having fun.


Good morning everyone. We are about to start. So thank you all for coming to the joint ENCODE and roadmap workshop. My name is Feng. I'm from Penn State College of Medicine. So I'm going to chair today's session. First of all, I want to thank you all for coming here so early on a Saturday morning. So that really made me really excited and that shows how much we like ENCODE and roadmap and hopefully they can be helpful for your own research. And by the end of this workshop, I hope you have learned something from us and it will always be here to answer all your questions. So today we have a tight schedule as you can tell on the screen. So we will not leave any time during the transitions but I do ask the speakers to stay after the workshop so we can be here for 10 or 15 minutes to answer all your questions. And then you are always more than welcome to email us about any potential suggestions for future workshops. And all our slides today has been uploaded to the ASHG app if you can find it. And then all the slides, tutorials including the videos and audios will also be available in that website, ENCODE.org, ENCODEproject.org early next week. That website can also find all the other tutorials we have done before. As a matter of fact, we just run a three-day ENCODE workshop back in July. It's three days so we can have more chance to interact with the speakers and the analysts who do the work. And we are in the process of planning another three-day workshop for next year. So look out for the potential emails or updates.


Okay, thanks. Yep. Yep. Yeah, it's been on. Yeah, Leslie did have that last time. Okay, so yeah, thanks for everyone for sticking around. So so Laurie and I, this is a talk that we initially thought of when we were together at Prague at the LinuxCon there about how a lot of the things that we've seen in our careers is really about collaboration and open source is obviously all about that. But we think it also provides a lot of business value. So we've got some examples from our business lives. Okay, so we'll introduce ourselves, Laurie. Hi, so yeah, I'm Laurie Apple. I'm a cartoon character and a senior program manager at Workday, which is HR financial management software company based in California, but with offices worldwide. I'm in the Dublin, Ireland office. My colleague Ali is in the back row. Hello. Thanks for joining. And I'm not really doing open source work these days anymore. But my, the teams that I work on are using Kubernetes Helm and a variety of other open source software programs. So so yeah. Okay, I'm Eric Redell. I was most recently spent nine years at Dell EMC building large scale storage clouds. I've been involved in open source probably 20 years, 25 years as an engineer, 15 years as an engineering leader and director. So I've built teams building open source. I've done open source projects across the industry. Before open source, we used to call them standards projects in the hardware space. But it's very similar in collaboration. So a lot of experience with with teams and collaboration. So we're going to try to share some of those with you today. So on our menu for today is communicating in technology. And of course, an open source, which provides unique opportunities to communicate in different ways than you might in your day to day work. Communication magic. Eric will go into what that's all about. Empathy is skill as a skill. That's me shared goals. I think that's both of us and inclusion and collaboration across cultures, which you might have to speed through as we wind down. But hopefully we will get to the exercise included there and then Q&A at the end. So communication is an art form. And to practice an art form successfully usually requires a bit of discipline. And so this slide is inspired by the work of Eric Fra, whose art of love was quite influential in psychoanalysis circles and psychology. That happens to be a hobby in an interest of mine, psychology, brains, neuroscience. So I saw it was at the end of the book. And I thought, well, golly, that's pretty applicable to how we talk to each other in software development. And when we're disciplined, things tend to go pretty well. And I'm not talking about rigid rules, but an expression of one's will, something that we develop organically over time, a disciplined approach to communication, communicating effectively, communicating clearly, and communicating in a friendly, warm, inviting, collaborative way. Concentration helps us to develop this discipline by becoming better and better over time through different exercises, exposing ourselves to different experiences, doing mentoring or asking for mentoring and how to be a better communicator. And it really is about introspection and listening to others, gathering feedback on how we communicate so that we can continue to do so more and more effectively. And then patience because this is a discipline or an art form that's going to take a lot of time. We all build habits over time and some of those are bad habits and it takes a while to break them. It also takes time to shift our bad habits into better habits. So these three elements which Eric Fromm had identified is essential to the art of loving people successfully in a very organic, natural, not rigid, not forceful, not controlling way. And also being able to really connect with other people that we're trying to love really, for me, because I'm, seemed perfect for this, for our world. A lot of times we think we are doing discipline, concentration and patience. We go to work, we show up on time, we go to the meetings, we work on our teams, but just doing those things on their own doesn't necessarily mean that we're living the spirit of discipline, concentration and patience if we're kind of on autopilot or we're not really contributing proactively to those activities of, you know, meetings, like do we enable or empower others during those meetings? When we're working on our teams, are we actually talking to our team members? Are we just sort of hoping that they understand this and letting it go? Hierarchies, which are pretty common in old school companies, don't make us collaborative either, even though they kind of assert that they are creating structure for all of us to collaborate, but it's really quite automatic in many cases. And if there are toxic hierarchies, then people are going to rebel, which is obviously not discipline at all. Okay, so if, what we listed out here is some common problems in tech projects, right? We've got missed deadlines, probably no one in this room, you're all well organized and never missed your deadlines, but it happens out in the tech world, right? There's complaints about low productivity, maybe somehow tied to the time, but if we only had more time or more people as comes lower down, maybe there's poor quality, right? And then people issues, often there's high turnover and everyone complains about the difficulty of recruiting, finding, you know, quote unquote good people, right? And I think many of us, there's certainly many of the industry that I regularly interact with just feel like it's always like this, right? That this is just the way that technology is, that it's always things are always going to be late, things you're always going to have to make compromises, etc. It's just the cost of doing tech business, right? And so the question is, does it have to be that way? Of course, everything on the previous slide is true. Projects do get slow, inefficient, they're unpopular to work with, they're not pleasant to work with on. But if we just give in to the lowest common denominator, we're never going to get better. We're never going to really maximize our potential. And collaboration can be the way out of that sad state of affairs. So let's talk about talking. In open source, these are some of the key ways that we talk to each other, GitHub issues, the pull request and code itself, Slack, meetings, meetups, Zoom calls, Google Docs, social media, one-on-ones, conferences. Think about which channels are most challenging to you. And also think about which channels you use most frequently and which ones seem to pay off, rape the most benefits for you. Maybe in technology, the assumption is a lot of us are not extroverts. So we don't really want to go out in front of a lot of people or we're not getting our energy out of these big, cloudy, social interactions that might require a lot of conversation. So maybe we do all of our communication online. But how do we do that communicating? Is it clear, effective, structured? Do we think about how the reader is going to be able to intercept information, really understand our point of view, and also not be hurt or offended by it, because it's rude or insensitive in some way. How, if you are struggle with communicating or you're just kind of new to the scene and entering a project for the first time or community and you really want to do well at collaborating and communicating, it's a priority for you. You can learn a lot from the land of therapy and psychology. So this slide lists 10 principles for what's called intentional relationship design, which is a popular concept in therapy relationships. So when a client goes to see a therapist for the first time, the therapist can't just be their friend. It can't just, you know, it can't be like going to meet your friends for coffee and telling them about your day. There has to be a boundary set to make the relationship effective. And, you know, that boundary can be easily smashed if the therapist isn't deliberate and vigilant about maintaining it. And so they also don't want to necessarily lead the client on to the conclusions. They have to be able to allow the client to arrive at conclusions themselves. And so these 10 principles were developed to help therapists manage that relationship successfully. So I'm not going to read them all out because they're right here for you, but being self aware, learning, which you know, we call growth mindset in the tech world, focusing on activities instead of like ideas or plans, but like actually doing things. So having results orientation, cultural competencies so that one can communicate and collaborate with as many people as possible, and mindful empathy, which, you know, will help retain. If you're running a project, if you're empathetic to the contributors and users, you'll retain them over time because they can, you're engaging with them. So why would one want to be intentional? Well, I think I've hinted at it already in the previous slide, but in open source software reasons would be to reduce or eliminate conflicts or drama, which are negative and toxic forms of communication collaboration, you know, collaborate on a big Twitter mess, you know, something goes wrong in community can all this point on Twitter at the outrage that ensues. Not a great use of time that happens quite often. That's waste and delays of energy, goodwill, contributors, time, effort. If you're intentional, you can avoid those by setting your boundaries early and often in the expectations for how everybody can work together. Confusion, again, setting boundaries can clear that up. Here's what we all expect from each other. Now let us go forth and collaborate. Misalignment, common in projects. Again, being intentional helps people to align. So and check in frequently to make sure they remain aligned, instead of just kind of going off on tangents. It protects collaboration builds trust, which is essential to any collaboration being successful, reduces cognitive load by replacing all that drama and awfulness with focus and sharing of cell and celebrating of work done. And it drives experimentation because instead of arguing and fighting, you're thinking about how to collaborate and brainstorm together and you actually had the time to do it. When we're not being intentional, we do all those terrible Twitter outragey conflict things. We make assumptions and jump to conclusions based on emotions. So that prevents collaboration because we're coming at a situation from a place of fear or anger. We don't ask for what we need because we don't think we can get it. We just give in. It's just opposite of being aggressive. It's being passive. We become frustrated and ruminate again being passive. This means we lose opportunities, because we don't ask for what we want or figure out how we can get it. And then we rely on my handwriting powers that we don't have. So we don't open up a conversation. We just assume that we know what the other person's thinking and give up. So we don't want to try these exercises here because there's not really time. But if you actually want to practice some communication skills, here are a couple of examples of ways you can do that. And you can actually apply these in your open source collaboration efforts.  So to avoid that, create scripts or templates in advance to help set up an empathetic response. So here's an example that we give you. Thank you for trying to understand my point. However, I think where we're still misaligned is blank. You know, what do you think? And then that's inviting somebody to communicate with you and it's a lot better than like, no, you're wrong. Goodbye. Another example would be, thank you for your enthusiasm. I've noted your concerns and believe we might handle this concern or situation by and then you make your proposal.  We don't have time.  And that's the magic that you can add to your project and your interactions and getting further into magic. Now is Eric. Oh, right. Yes, I just want to give you a microphone. I'm good for to communicate better, right? Yeah, so there's a so that those the types of things that that that Laurie talked about there are sort of guideposts in communications, right? And so so I want to kind of change a slightly different story from from my recent experience on my most recent project. So so as an engineering project, large corporation, like I said, we're building big cloud storage systems at the height. This was a 250 person development team spread around the world, you know, only maybe a dozen people in any geography altogether. So there was there was a lot going on right a lot of a lot of communication. And and one of the explicit decisions that we made in the leadership team at the beginning is that that we were going to over communicate in this in this project. So there was a lot of communication. And and what we we took away from that was that there was a lot of benefits, right? A lot of secondary benefits that maybe we hadn't quite intended, right? So we so what we did the way we initially implemented this starting maybe five five years ago is we did these massive mailing lists. So so there was, you know, at the beginning, maybe there was only 30 of us. But even as we grew to 250 people, when a new person joined the group, they were added to an alias that was a list of all the engineers on the team. And there was also an alias for escalations if there was a problem with a customer that was a link to the list of all the engineers on the team. And there was an alias for new design ideas if someone wanted to propose some new aspect of the system. And it was a link to the same distribution list of all the engineers. So you can imagine, you know, people had all kinds of filters for their email. A new employee was warned that, you know, within two days of joining the group, they'd be added to these email lists, and they'd be getting, you know, up to maybe 100 messages a day. But what it embodied more than just sending out lots of emails was that the information was available for people. And that was used in actually a lot of ways. For example, like the archival history meant that folks that were coming to a problem fresh that maybe they hadn't paid attention to, they actually, so most, the way this happened most often was an escalation.  My team was responsible for the hardware, for example. There'd usually be a bunch of debugging and diagnosis and other things would go wrong before someone would decide that it was the hardware's fault, right? But we had, in our inboxes, whenever something like that would occur, we would have a long archive that we could go back to even if it first happened a month ago with this particular customer, as long as we had the right keywords, the information was right there. And the same thing with design discussions, right? So like I said, we had, you know, an alias, the design discussions that went to everybody and people got used to kind of ignoring, hey, this is really not my part of the system, et cetera, but you had that archive, right? In addition, there were often folks that were in remote geographies or maybe they were, you know, new to the team and were acting a little bit more in a support role. The QE team was also included in this, as part of the engineering team. And so there was a lot of people that had small, that were able to pick up small bits of information because we were spreading it very widely. Whereas if we had just centralized the information or tried to work out different streams of who needs what information, which all of us had experienced in previous projects, we would always miss somebody, right? So that was a great way to do shared state. And sort of luckily for our email inboxes, about two years into the project, we started using Slack. So we were also able to introduce with Slack and the combination of the emails a way to have more real-time responses so people didn't have to constantly monitor their email. But the important point that I wanted to, you know, that I would take away from this is that we massively increased the amount of information that flowed through the organization.  But the baseline was that we sent probably an order of magnitude 10x as much information into the organization as any of us had experienced on past projects. And it was better rather that the upsides far outweighed the downsides of, you know, the scary new person who's like, oh my gosh, I'll never be able to recover again from all the emails. So there's an example. Okay, next part. So thinking about that person and recovering from the email shows empathy. So let's talk a little bit about empathy and how it's a skill. And this isn't an idea that we came up with. It's kind of floating around the internet. Andrea Goulet, who's the CEO of Corgi Bytes in I think Virginia. She's on Twitter. I think she's writing a book about legacy code and empathy involved in managing her legacy code. She kind of propagated this idea a couple years ago. And it's a good one. So just so we know what empathy is. Here's the old online dictionary definition. It's a psychological identification with or vicarious experiencing of the feelings, thoughts or attitudes of another. The second one isn't so pertinent to our purposes here. But it's really emphasized what this word is about. It's really trying to identify with somebody. It's different from sympathy where you actually feel sorry for someone, which could even be like a power dynamic, you know, I feel so sorry for you all. But empathy is like, I understand you, I get to. I'm going to do things so that you feel like a real person that matters, because this is how I know that, you know, how to make that possible for you. By building a great software project that's not hard for you to use, but has a great user interface, has good documentation. I'm going to be nice to you so that you have a good experience in that way. If you're a contributor or user, you're going to feel comfortable coming back to me in my community. So this is how you empathize. One good thing to do every once in a while is do an empathy audit of ourselves. And why would we do this? Well, just to make sure where as empathetic as possible. This is, again, a discipline like communicating that one can develop over time and constantly get better at. And there's lots of benefits of doing so. You know, we all tend to like friendly or empathetic people, because they make us feel good. So on a scale of one to five from low to high, how would you rate your own empathy? You know, that might be hard, because you're like, well, I don't know. I don't know how to do that. But go to the internet and find examples of read about empathy and how to be empathetic and then get, you know, figure out your own metric. When you aren't communicating empathetically enough, what does that feel like in your body and mind? Usually when we're not communicating effectively or nicely, we'll feel it. You know, feel a little twinge of guilt. So, you know, what is that? Reckon with that feeling. Reckon with the thought of that. Oh, I should have done better. You know, like sit with that and think about, well, how could you do better next time? When you're communicating empathetically, how does that feel? You know, we might feel very good about that experience and it's good to sit with that feeling too. And then, finally, do you reflect on your communication to improve your collaboration? Do you regularly think about how you communicate and ask people for feedback and see how you can do better? Some exercises to reinforce your empathy journey is that when you're frustrated with somebody or something, just stop.  So, like, I've heard this before in certain open-source communities. Well, you know, we're just so busy, merging all this pull requests and reviewing all this code. You just can't stop. You can't stop. We're like robots. But you know, what if you're, you know, that's kind of a perception that we develop in ourselves. You can stop, even if it's for a few moments, before you say or do something that you might regret. Like, you're rude to someone. So, you know, pause. It's the easiest way to avoid a lot of trouble. Just pause. If somebody really makes you angry, just get up, walk away, come back.  And if this is a real problem for you, like, if you are kind of wired to be, like, going after folks on a regular basis or you have anger management problems, journal, talk to a peer, go seek help. It will make you happier in the long run, because it really doesn't feel good if we're always just going off on people. We're going to help you get started now. We're going to throw in a minute of meditation for you. So, if we can set the clock, I guess we have it right here.  Who actually does meditate on a regular basis. Okay, a couple people. Yeah, it's gotten popular. So, if you haven't done it before, here's your chance. So, count your breaths. As you inhale, we're starting the minute here. So, as you inhale, just silently think one. So, breathe in, one, and then exhale, two, and then inhale, three, exhale, four. Inhale, five, exhale, six, inhale, seven, exhale, eight. Inhale, nine, exhale, ten. Inhale, one, exhale, two. Inhale, three, exhale, four. All right, so that's a minute. You can do this three times. You can do this 100 times at home. There's other ways to meditate.  Think about your feet. Think of your thoughts as little pieces of ice floating down a river. You know, there's always you can do this. But the idea is that you could just kind of think about your thoughts and detach from like all of the craziness that goes on in all of our brains. You know, we're constantly thinking about things, usually in a very rapid fashion. And if we don't take a step back sometimes and we just allow this to happen, we can get very stressed out very quickly and also not become in touch with the effects of all of these racing thoughts on our mood. So I think we only have two minutes, two minutes left. Oh really? Oh well, okay. So I guess we'll hurry up. So a couple of ways to empathize with people in addition to becoming a Zen master and chilling out and being mindful or setting up a personal readme. We all know what readme's are so just make one for yourself. How do you operate? What are your pet peeves? What will make you ragey and stressful or annoyed? How would you like to be communicated with so that you don't have a negative mood response? These are some of the things you can do. Yeah, I still don't need that. So then there's another section here in the slides that you can look off offline about building shared goals among a team with brainstorming techniques, other kinds of techniques to get the team communicating together. Obviously that's, you've seen now a big theme in my experience is getting people working together, brainstorming ideas, deciding goals together, rather than working off of lists or some kind of top-down. It's a great way to operate within a team. Actually a lot of, a lot more details. A lot of details there in ways that you can focus. Like I say in a future talk we can get you updated on that. And then the last part we wanted to talk a little bit about is inclusion and having that perspective. I don't, do we want to try to do another exercise or? We can tell them we're in a hallway. Yeah, okay. So why don't you, so why don't we leave you this as a homework exercise afterwards and then we can take a couple questions. So the way that we set this up was, you know, think about some of the things that make you more aware of how you're responding, you know, why you might have difficulties with a certain communication, other communications, etc. There's a lot of background to that. And the exercise that we did when we did this in Edinburgh would to ask people to talk with the person next to them and talk about two cultural things that may not be obvious from just physically looking. And we're not going to ask you to do it here because in Edinburgh we lost control of the room. When we asked people to talk to each other, we were really afraid that no one was going to talk to each other and everyone was just going to stare and we were going to be stuck and ultimately everyone just kept chatting and we were like wait, we're still here, we have two microphones. So we'll leave you this as an exercise after the fact, but this is is super powerful even in a work setting, you know, not sharing everything about yourself, etc., but having a way to connect at, you know, at a cultural slash human level. Yeah, you might find your next collaborator here, if you're an event tonight and you say like oh, what are two things about you I would never expect. Oh, here are two things about me, and then you can start a conversation as our group, our audience did in Edinburgh, like that you might not want to stop, but we won't be there to tell you to stop. Right, or you could do it after after Leslie does the housekeeping, lets everyone go. So we can, I guess we could take some questions, I guess we have both microphones, so we, our own.


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Turn it over to Dustin for the Q&A. Dr. Philippon and Dr. Mack, a lot of people are interested in some details on FAI screening. And each of you spoke about physical examination, Dr. Mack spoke about 3D biomechanics. When do you go from physical examination guiding your screening to deciding that you need to step up and start with some imaging and then how do you pick your imaging at that point? Dr. Philippon, do you want to take it first and then we'll switch over to Dr. Mack?  So initially we have a fast screening process, like a demonstrator with a favor distance, the impingement test, asymmetric range of motion. But sometimes we can have a patient where there's a label separation. And sometimes I'm trying to quantify how big it is. And what I like to do at that point, because sometimes we try, we have paid athletes, especially they come in, and they're trying to decide if they want to pursue their season or not pursue their season. And sometimes what we'll do is we'll use the ultrasound and I think it's very effective. Use the ultrasound, do an axial distraction test, and also put the hip inflection and just look at the conflict. See how large it can, how much displacement there is with the labrum. And if the labrum is not too unstable, sometimes we'll suggest to our patient, hey, let's get an injection. Let's wait, let's work on our muscles, and we'll try to do this at the end of the season. So for me it's very helpful to do an ultrasound, clinically, just to decide if we should postpone the intervention, surgical intervention, or just try to stay conservative for a little while longer. Okay, and Dr. Mack, do you have any additional comments on that question? So I would agree with what Dr. Philippon has said. I've had a similar experience, and we use dynamic ultrasound as well in our clinics. Oftentimes we will get preoperative MRI. I don't personally do Arthrogram. I haven't found it useful, but others have. I am a very big proponent of the diagnostic injection. Using corticosteroid injections under ultrasound guidance has been helpful to me if athletes need to get through a period of time. However, I do not allow them to have more than one, and I caution them they cannot play within a few days of having the injection, so the numbing medication must be worn off to ensure that we are not masking any potential pain protective mechanisms of the hip. So in those two fashions we try to get individuals through their ability to play their sport. That being said, obviously ultimately if the hip continues to be symptomatic and they are playing through pain to the point where they can't, then that becomes a surgical situation. So Dr. Mack, you discussed the corticosteroids. What are your thoughts on the, and Dr. Philippon will bring this to you next. What are your thoughts on the current state of orthobiologics for FAI patients and for soft tissue lesions, and then the future? What do you think the future is taking us? Dr. Mack, we'll go to you first. Sure. So we do a fair amount of research on that, specifically as it pertains to the cartilage that I presented. And the conclusions we've had is, candidly, we're not there yet, but we probably will be. We have a number of trials going on currently where we can take individuals, both polydactyly cells from kids that don't need it. We can culture them and are actually in an early clinical trial utilizing that, and that can be placed arthroscopically. As far as non-surgical biologic utilization like PRP, stem cells, things like that, my own perspective is the data is not there yet. As far as stem cells are concerned, maybe it will be one day. We don't use it currently. As far as PRP is concerned, it has a role. Lucasite poor PRP has been utilized well in my patients as well as others. As far as symptom management, it's not obviously going to protect the hip from damage or anything of that nature. But to get a hip to calm down, Lucasite poor PRP has decent success. It's something that we use ourselves. It also has very little condor toxicity, unlike cortical steroid injections. So we use that in our athletes for that reason. Dr. Philippon, I know your center is doing a lot of research in this area. What additional thoughts do you have, and especially looking towards the future? Yeah, I agree with Dr. Mack. I think right now we're starting a trial where we'll NIH fund a trial, where we'll look at bone marrow aspirates and look at the effectiveness on the culture generation. Also, we're very interested in synolytics. We're looking at it as well, phycetin, cursetin, and pre-bone marrow aspiration to minimize the senescent cell and have a good yield of good stem cells. So we're doing a lot of research on that. What I do in certain athletes, I'm not saying we have a 100% success rate. A lot of them, to get them through the season, will do an ultrasound guide injection over the conrolable separation with PRP, lococyte-poor. And we've had good success, and maybe a third, a fourth of our, a third to a little more than a third of our patient with that. And that, what it does in our opinion, create a little inflammation, it'll scar and stabilize the conrolable junction temporarily. And I've had a few patients where we inject PRP and they can go on for a year or a year and a half and postpone surgery. Now, it's not going to treat the impingement, obviously, but it's a good way sometime. Let's say the Olympic cycle, someone is ready for the summer Olympic, we'll try to get them through the Olympics if they get hurt a few months before because they cannot have surgery and get them through if it's possible. And as I said, for us in our hands, a little more than a third of our patient can have a good response to that. A lot of people are interested in return to activity rates after hip arthroscopy. And from my experience in working with both of you for a long time with Team USA athletes, I actually don't know of any athlete who did not return in our program, which is pretty impressive and I don't think is in the literature. But I know you guys know the literature by heart. Dr. Philippon first, how does return to activity after hip arthroscopy look for elite athletes? Well, that's a great question. Now, if we look, there's different cohorts. If you look at the pro athletes, we looked at it by sports and we have published that in the American Journal of Sports Medicine and other medical journals. So we look at ice hockey players, for example, high soccer players are cohorts and NHL hockey players return to play was 100%. Baseball player in the 90 plus percent return to play, measuring baseball pressure, NBA basketball player. We just published that recently, 100% return to play. So I would say an NFL actually was a little lower. It's I-80s. Overall, you could say that return to play at the professional level after an intervention like we do is at least 90% plus chance of return to play at the same level. Now, in the recreational athlete might be a little different because you're dealing with different muscle structures, muscle strength and training and all that. But overall, let's say return to sports at the same level. That's it's certainly around 90% plus. That's phenomenal. Dr. Mack, what additional thoughts do you have on that topic? I think you might be under. So I would agree completely with what Dr. Philippon said. And that's it was the part of this talk that you just heard was the specific differences between recreational and professional athletes. And there are very big differences that I think it has to do with the stresses on their hip. And one would think that elite athletes have higher stressors and they do, but they also are far more able to accommodate and they have better neuromuscular kinematics. So our experience has been the same that the study that I quoted that showed a 74% return to sport in my experience, that is unquestionably on the low end. And my experience has been the same as Dr. Philippon's where we're upwards in the middle, middle to high 90s. NBA athletes interestingly are a unique cohort depending on the specific position you're in. It may have a higher or lower percentage, but I think elite athletes are unique and surgery works when it's indicated when elite athletes extremely well. And I would caution the audience that these results are definitely better when you have a very experienced surgeon. This is a fairly new technique and they're inexperienced surgeons. And we've seen that when we use very experienced hip arthroscopists we see phenomenal results. Our next question is for Dave. Dave, people had a lot of questions about the athlete 360 program. Is it something that can be bought? How is it developed? Can you expand on the history and the current state of the athlete 360 program? This is a bespoke program where we've actually partnered with our team at KINDUCT. It started off the back of, as Dustin and I sort of presented in our presentation, that it was initially just a screening program that coupled with something that inspired actually out of World Bar's questionnaire that he mentioned earlier today. And then it's progressed across time. It just started with one team. Now we're servicing over 500 Olympic and Paralympic athletes across probably what we would say, 17 different NGBs. And I heard that term mentioned earlier in 26 different sporting groups. We're not quite to the whole of Team USA, but we're definitely our outreach is continuing to expand. And especially during this time where we're sort of distance-based training and contact with our athletes has been imperative in us understanding their wellness and that individualized training load. All right, so we're out of time for this panel. Thank you, Dr. Mack and Dr. Philippon for everything you've done for Team USA. We're extremely appreciative of your expertise and for your centers contributing to our national medical network. And that's the end of this session. We're going to kick it over to Charlie.


अगर जो सकब नाग़ बद्ख्षत्री ने जगैंगे लिए मिलगतार, षक्द्ष ख़र, जी चो बाग़ा जोगा पद कुँँँँँँँँँँँँ, आंम of the random walk and we have discussed separately with drift then we have discussed separately with drift then we include the trend, when will there be a pure random work? Solve a trend in random work Then, what type of shape will come Then we discuss this type of shape separately Now we are going to discuss the comprehensive model of random work to discuss which options are possible in the possible options we have three options we have the random work आनका books अं। इंका आनका अग्छ हमा उआनने कि आद्चा integer अद्चा楠 dengan औगग अगर अप् YEAH । अदर् pin आदर तर minim लेग, after this we will know that if the constant of the value of the value of the value is zero, then if beta is not equal to zero लेग सी, it means like a constant, there is a drift in the model लेग सी, and beta is not equal to zero, it means there is some determinisctin in the model लेग सी, and beta is equal to one, it means there is non stationary series या ती मैंस वान्त की एक कलूज एस्वॉस्याशिएशन अगजिष्त करती है और इसके बाद हमारे पास जो नया माडल बनेगा this is yt is equal to β1 plus β2t plus yt minus 1 because its coefficient value is equal to 1 and we can say this is random work with drift and deterministic trend now how can we explain it, we have the example we graphically look at it, in this lower portion of this graph you can see AR1 with constant and trend here you can clearly see a trend that there is a positive trend when there is a positive trend, we have applied the AR1 process or we have defined the difference when we have defined the difference, the trend will be over and the trend will be over now your values will be over this is de-trending and in de-trending you can see the mean is constant with the passage of time and the variance is also constant because you can see the mean is here and here the mean is here and the mean is here in every next step, the mean is almost constant now the upper portion of this graph you can see there is a minor difference upper and middle again, if we look at the mean and variance of this graph this is again almost constant but in the lower portion of this graph you can see the mean with the passage of time is increasing now when the mean increases the situation will be different in the middle portion, the mean is constant and in the upper portion, the mean and variance are constant there is a minor difference in the upper portion, there is no trend there is no drift because the value starts from zero but when we come to the middle portion there is value of 1.5 1.5 is starting 0 is not starting if the value is starting from zero it means the random walk is with drift and without drift the idea will be that if the upper portion of the graph starts from zero we will say this is without drift but in the middle portion 1.5 is starting it means there is drift in the model and in the lower portion you have a deterministic trend so from here we will have an idea that when we ask for the option that you are going to include the drift or not so first of all you have to look at the graph so from the graph you will have an idea whether there is a deterministic trend you will have an idea that you have to include the drift or not to include the drift so the first step in the time series when you plot the time series the idea will be that this is deterministic this is pure random walk there is drift there is no drift how to detrain it how to take a difference you will have an idea of this from here


Researchers have just found a gene that links East Asians to educational attainment and is this the most stereotypical thing in the world? Let's talk about it. Yeah, you know, we're talking about new genes, but apparently we're born with a nerve gene. A study conducted by Korean medical researchers in collaboration with the Taiwanese team involved a genome-wide association study Andrew with samples from 176,400 individuals and they discovered that they were tracking extra high on this chromosome that has been labeled edu years That's a funny name for the chromosome, right? So basically Andrew Potentially being nerdy and good at school is a little bit genetic Hold up. Hold up. We're gonna talk about this because does that mean? Nature versus nurture. What does it mean to have this gene show up a little bit more or a little bit less? Maybe it doesn't matter. Maybe it's more on the place that you're born into anyways guys, please We're gonna get into it.  No chur. I will say this By the way, Andrew the study also followed up by saying while the study unveiled a genetic link the researchers Caution against using these variants to predict an individual's educational achievement Emphasizing the influence of social and environmental factors Andrew They also did a quantitative estimate saying that this extra if you like rank really high on the edu years chromosome It estimating it only gives you a 10% of variance in total education attainment However, it's 10% a lot if you get slotted into different lanes early in life Well, we're gonna talk about it man because I guess I got some thoughts on this because I think that Assuming that this is true. I mean these are researchers. They did find this gene I'm not in the lab with them. So I'm not gonna tell them that it's not true But I think the debatable part is how much of an impact that has on your life Because your life is made up of a ton of different factors It's not just the brain that you're born with it's literally the family. You're born into the environment Do they care about education all these other things? Do you care about education? Maybe you find out you're into other things and then you don't go into Because education attainment what they're talking about is literally attaining like a degree But you can be very smart and not attain it or it could be street smart. Yeah, it could be merchant smart I mean, there's different levels and different types of intelligence. Well, well, let's just get into some stats Andrew How true is this because 6% of the Asian American population is Asian But they make up 41% of the students this score over 1400 on the SAT. So obviously like it's not like anybody was really like I Mean, I guess it's like a stereotypical Doesn't is it does it not sound stereotypical like did you know there's also studies about Kenyan lung capacity? Because Kenyans typically win all the long-distance sports in the Olympic in the Olympics and Jamaicans are heavily Overrepresented in the sprinting sports, right? There's actually studies around this. Yes. Yes. Yes I mean, I guess you would say very athletic people. They generally have a higher What fast twitch count in their muscles? I have to do something between the transfer of oxygen through the blood through blood pass.  But so then it's higher, but then there's still obviously a lot of athletic non-black people.  Well That's not mind-blowing Right the black guys dunk in the ball the Asian guys dunk in the books Yeah, that's what you're meant to do now now due to our genetics We're all meant to do that but it only accounts for 10% and really your environment is gonna count for everything else However, it is true that in America, let's say for example, Andrew We're slotting kids into like different lunch tables that 10% could make you excel at something and then make you identify with that thing And then that lane in life, whichever one lane you end up getting slotted into your cultural position and do the fishbowl You're born into it keeps on rolling from my right, right. Yeah, but then at the same time I mean, there's a lot of people who fall out of academics who are smart a lot of people are born smart that never, you know Maximize their capabilities. There's this one quote from another study. That's part of this article and it's written by the scientist The conclusion I draw is that despite the relatively high genetic irritability shown in most brain processes associated with learning meaning that yes some level of brain power is inherited. We this is not shocking, right? Educational practices are a key contributor to a student development allowing genetically based skills to be enhanced or alternatively Diminished therefore one of the main goals of education in a changing and uncertain world should be to form Adaptable and versatile people who can and want to make the most of their capabilities So it's all about maximizing yourself at the end of the day for sure And there's this whole new field of epigenetics which means in the first three three to five years of your life Your genetics can actually shift a lot of people thought your genetics were like stuck in a womb or whatever like that I'll say this growing up in a I would say highly academic Chinese family Andrew I'll say this being conventionally academically smart from like a metric Analytically trackable level was extremely important. It was your identity It was your self-worth and for better or worse Andrew, obviously, we know not all Chinese families are like this But a lot are right your self-worth and how you see yourself in the mirror is tied to how well you are doing at school Social pressure is huge And then once you kind of get into that flow once you've been pushed to achieve high and then you can already achieve High and things become easier then you're just gonna keep doing that and it makes sense, right? But well, that's what you do as a person. That's what you're built for essentially at that point It's not what you're born for it's what you're built for like building Happens throughout your life being born is one thing and you are born a certain way But there's also things that can change you in your early in the truth It's not everybody has a huge ass energy bar to take every rep of everything They do in their life with 10 out of 10 intensity, right? But I'll tell you this in a nerdy Chinese family or nerdy Asian family Andrew any math problem science problem Verbal thing related to the SATs you're taught to approach every rep So seriously and it kind of reminds me of the way Denzel is training his son at basketball and he got game Or I looked I was looking up some footage Andrew of Luca Donchich training when he was 12 years old with these crazy rubber bands around him People are hitting him with like the training sticks and he's shooting jumpers with rubber bands tied around his body Look at how intense they're taking those reps, but just imagine that But for something more academic, right? So yeah, it's just all about your training and Yeah, anyway, let's just get into the comment section Somebody said garbage study did not consider social historical cultural geographic attitude considerations meaningless I mean they didn't mention that in the article. They mentioned that Educational attainment is a very specific thing. So it takes a lot of environmental and factors and structures Because you can't attain any education if there's no school in your village, right? You're saying let's say for example, you have really high edu years chromosomes, right? But you're born into a country that has no political stability or a lot of infrastructure instability or like natural disaster You're born on a farm 50 miles away from the nearest school How are you gonna achieve high in school when there is no school for sure for sure? You I guess you'll never get to utilize those things You know what it kind of reminds me of to enter there's a lot of P Really tall players that are born in Africa right now, but they're not getting the NBA training to go to the league Right, they're playing soccer growing up until somebody finds them, right? Anyway, this comment is from a white guy. It says that's bogus. It's the culture Western society has put past all the glory years and now everybody is just going towards a balanced life Asians aren't there yet. So they are still mostly driven by their parents and they say Asians are now at the forefront And want to succeed a competitive world. This is Asia's time essentially, right? This white guy is basically saying like come on man. We already did all that man last 300 400 500 year We just chillin now, right? So I guess Asians are still got that like Kind of like hey, I'm new to this. I'm working hard type like I'm an immigrant. No, I mean There's some truth to it like let's see and or let's analyze the old money families in America The guys who like built up all that wealth in like 1890s or 1920s, you know like Rothschilds or something The Rothschilds that exist now. They're just chillin, right? But the guy somebody had to do the work somewhere, right? Um Some guy says this study is so goofy. Why are Japanese so low on the Educational attainment chart compared to other like for example like Indians when you said Japan is a much better country But actually what people don't understand is it does have to do with immigration waves because most of the Japanese that immigrated to America in the early 1900s Andrew were actually uneducated farmers Like that's you know what I mean like from to Hawaii or the West Coast, right? Right, right. Right. So like like we said this guy was also pointing out that immigration ways how people came Also explains a lot of like group inequities, right, but there I guess they're ranking Asians in Asia because they did Taiwan and Korea so the study is with Taiwanese and Koreans not in America, but you know, but people were verifying this study with undergraduate attainment statistics in America So that's why you know no like it correlates interesting ultimately man, I'll say this I'm not really that surprised I don't even know how much I believe in it But I just know that the culture you're raised in and what you are taught to see in the mirror every day And what that person is supposed to deliver on every day That's about a function of like ten thousand or at least a thousand different factors when you're being raised Yeah, I agree, you know, I mean let's say The attainment accounts for 10% what's the other 90% right the other 90% is big Yeah, obviously if you're smart from a young age and you're told that you're smart and You do feel smart then you're gonna identify as a smart person and then you're gonna continue to do smart things That's and you're going to develop normative behaviors with a reference group that you also identify Yeah, and then you're gonna hang out with smart kids Your friends are gonna be smart blah blah blah I knew this girl who was an adopted Chinese girl Okay, and she was born into a family with one other adopted girl that was from Chinese and one biological sister And she said that she was the only one that identified with the nerdy Asians growing up in the suburbs of North Carolina Of Chapel Hill and then ended up getting a scout full ride scholarship to college when neither of her other siblings did Right they grew up in the same family Because she said they grew up in the same family But she just happened to relate to that like boba drinking meme sharing crowd that was like all into it That was her friend group. So she developed normative behaviors. She hung out with the SAT squad Yeah, because she looked like them, but then she said even her adopted other sister didn't do that Yeah, well, you can even be from the same family and experience different things Is it just her 10% gene that made her want to just be so much smarter. There's other factors too. So I guess I Guess, you know achieving a Educational degree there's so many more factors to that than there are even to just Being smart and having a high IQ, right and even achieving a high IQ There's probably still factors that play into that. So everything Yeah, it is true that if we want to get into ancient history Literally East Asia or Confucius or like Confucian culture or scholastic culture or like China invented national exams though Yeah, I mean wouldn't the people who invented something Typically be pretty into it. Yeah, that's a whole nother story though I'll pop up some links anyway guys Let us know what you think of this study in the comment section below Is it valid not valid valid nature versus nurture versus nurture? Who knows? We encourage the debate until next time with a hop-hop boys. We out. Peace


Hello friends. My name is Mahirubali. I am an assistant professor in WIT, Singapore. Today we are going to learn about activated sludge process and its analysis. So what are the learning outcomes from this session? Basically we are going to learn about what is the analysis of activated sludge process in wastewater treatment. So let's study that how we are going to do whole this process just to create the activated sludge process with a proper quantity. How much we have to add the BOD? How much we have to fix the detention time of aeration? Then how much we are going to fix the nutrient content? For these whole questions, we are going to study about the four analysis and the four criteria for activated sludge process. Let's study first one is hydraulic retention time that is HRD which is mostly focused on the detention time of wastewater in the aeration tank. The second one is volumetric BOD loading. How much BOD we are adding in the aeration time? Organic loading which is F by M ratio. What is F and what is M? We are going to study further. Fourth one is solids retention time that is SRD. Let's study the first one hydraulic retention time. It is mostly the volume of aeration time with respect to the detention time on which we are putting the wastewater into the aeration time. How we can calculate it? We are calculating by using the formula V by Q into 24 where V stands for volume of aeration tank in meter cube and Q is the flow rate in meter cube per day. So understand the concept of formula. Here it is a volume and it is a discharge. So by dividing it, we are getting the time parameter and what it is representing? It is representing the time of wastewater in the aeration time. The next one is volumetric BOD loading. So how it is different than the HRD? BOD loading means how much carbonaceous matter which is present in the wastewater is going to applied in the aeration time. Now we have to understand see the volume of wastewater is different and the BOD loading is different. It may happen that a required volume of water can be increased BOD and it can be with the reduced BOD. It means the typical volume of wastewater can have higher rate of carbonaceous matter present in it or lower rate of carbonaceous matter present in it. So while adding the wastewater into the aeration time, we have to calculate how much carbonaceous matter we are adding into the aeration time. So for that we have to calculate a BOD applied per unit volume. How much carbonaceous matter we are going to add? Because the carbonaceous matter and the quantity of carbonaceous matter will give us a proper formation of microorganisms and secondarily a activated microorganisms. That's why we have to calculate how much BOD we have to add. So how we can calculate it? First we have to calculate by experimentation how much BOD is present in the wastewater and it is termed as LA and it is measured in MG per liter. So it is multiplied by the flow rate of wastewater and divided by volume of aeration tank. This formula will give us a volumetric load in terms of Kg BOD5 per meter cube. Now what is F-bomb ratio? Here F means food. What is our food? It is carbonaceous matter which we are going to degrade. It is the food which is measured in terms of BOD5 which is coming into the aeration tank and M stands for microorganisms which are present in the aeration tank. They can be coming up from the activated sludge or they can be coming up with the food also, with the influent wastewater also because the influent wastewater also contains some amount of microorganisms. So addition of activated sludge microorganisms plus the influent microorganisms totally it will give us the microorganisms present in the aeration tank. Don't confuse which microorganisms basically we are going to take in it. For the particular proportion which we want to get in the aeration tank with respect to the nutrients which we had seen in the earlier, the C into N raised to P we maintain the nutrient proportion in the aeration tank for the proper degradation of carbonaceous matter. For proper proportion we have to fix the F-bomb ratio. So how much we keep it? Typically it is kept by 0.25 to 0.6. If you see here this is our food and these are our microorganisms in the aeration tank. So for the proper decomposition of proper degradation of carbonaceous matter by microorganisms we have to provide a proper food and proper microorganisms. If anyone of these fails to maintain this ratio whole activated sludge process is going to give us the poor efficiency. For a greater efficiency we have to fix our food also and our microorganisms also because these both points are very much important for us. There must be one producer and there must be one decomposer. Then and only then the food chain will properly grows the food chain is properly maintained and the same logic has been applied in the activated sludge process also. So how the F-bomb ratio is important for us and where we are focusing on. In the earlier session we had studied about the declination of food in the tank and the increase of microorganisms to the peak and declination and going towards the regeneration process of microorganisms we have studied. In this growth phase where our food to microorganisms ratio is going to be focused is more important for us. If you see if we are putting the higher F-bomb ratio it means the food is present too much at a higher than the microorganisms at that time the dispersed growth will be form of microorganisms it means a very less quantity of microorganisms are going to form. So these stage will not give us a proper activated microorganisms which we are required as the activated microorganisms. So these phase will going to fail us. Now the second one is ideal F-bomb ratio. In the ideal F-bomb ratio the microorganisms are very higher rate than the food. Here the food is in the minimum condition and the microorganisms are relatively higher. What they will do they will take all this food from here and they will decrease the food and they will increase themselves. Fine in the aeration tank and then a large quantity of a flocked formation region will be there in the aeration tank. So this condition is our ideal condition. This condition will maintain the food to microorganisms ratio because food is continuously coming up. It is not a batch process it is a continuous process. So food is continuously coming up and it is going down continuously coming up and going down. That is what we wanted. These food we have to decrease it and we have to maintain the microorganisms to the higher level. If we are putting the microorganisms in the higher level then and only then the activated microorganisms are going to increase. So this condition is our favorable condition. Fine then if we are putting the low food to mass ratio. Now you have to understand here the microorganisms are going to decrease and relatively the food is very much lower. That's why the food to microorganisms ratio is what we call a lower ratio. Now you have to understand here also a very dispersed flock generation will be there. Therefore these microorganisms will giving out our dispersed flock. That's why we don't use these kind of food to microorganisms ratio. Now how we can calculate the food to mass ratio. Here we use F-bomb ratio where the food is calculated in terms of BOD in mg-polluter and microorganisms is calculated in terms of PPM or mg-polluter of MLSS. That is our small XT. Where F-bomb ratio is calculated as Q into La divided by V divided by 1000 into Qt. What does it mean? Q is a flow rate, La is our BOD and V is the volume and XT is our microorganisms in MLSS which we calculate experimentally. The fourth one is solids retention time. Here as we are adding food as we are calculating the microorganisms and simultaneously we are calculating the carbonaceous matter. After eating there is some degradation and there is some formation of sludge. Whatever the sludge and the MLSS combined together and the presence of such kind of a combination in the aeration tank gives out SRT. It is a time in which this sludge is present in the aeration tank so SRT is highly different than HRT. HRT is the volume of wastewater and SRT is the volume of sludge or MLSS which is present in the aeration tank. So both are different. SRT is donated as Qc and it is formulated as X divided by delta X divided by delta T. Where X is a total microbial mass present in the reactor which is our aeration tank and delta X divided by delta T is the total quantity of solids withdrawn daily including solids deliberately wasted and those in the effluent. So let's have some review questions. First one is increase in HRT reduces efficiency of ASP. True or false? F by M ratio reduces by increase in and reduced by CRT. Third one in ASP increase in return activated sludge increases. So answers for the review questions are increase in HRT reduces the efficiency of ASP it's true. F by M ratio reduces by increasing the COD and reduced BOD. In ASP increase in return activated sludge increases F by M ratio SRT, BOD file loading rate and all of the above. These are the references I have used for the making of this PPPT. Thank you.