Wednesday, October 22, 2014

A blade of grass makes sound- Sound Sandwich

If you pick a blade of grass or a leaf, stretched it in between your fingers or thumbs, and blow into the gap you will hear a high pitch sound. A lot of our students have had played with this effect. The working of a sound sandwich instrument, which can be made using simple items like craft sticks, a straw, one wide rubber band, two smaller and a narrow rubber band is no different in working as a blade of grass sandwiched between fingers and thumbs.
How to make a sound sandwich?
Stretch a wide rubber band length-wise over one of the craft sticks, and cut two pieces of straw, each about an inch to 1 ½ inches (2.5 to 3.8 cm) in length.
Put one of the small straw pieces under the wide rubber band, about a third of the way up from one end of the stick.
Take the second craft stick and place it on top of the first one, wrap one of the smaller rubber bands around the end of the stick a few times, about ½ inch (1.25 cm) from the end, on the same side where you placed the straw.
Make sure the rubber band pinches the two sticks tightly together. Take the second small piece of straw and place it between the two craft sticks, at the opposite end. This time, though, place the straw on top of the thick rubber band, so it sits just under the top craft stick. Wrap the second small rubber band around the loose end of the stick, about ½ inch (1.25 cm) from the end. When you are done, both ends should be pinched together and there should be a small space between the two craft sticks.
When your sound sandwich is complete, put your mouth in the middle, as if playing a harmonica, and blow. Notice that you can make different sounds by blowing through different areas of the instrument, blowing harder or softer, or by moving the straw closer together or farther apart.
What’s going on?
When you blow into the Sound Sandwich, you make the large rubber band vibrate, and that vibration produces sound. Long, massive objects vibrate slowly and produce low pitched sounds; shorter, less massive objects vibrate quickly and produce high-pitched sounds. The tension of a rubber band also will change its pitch: higher tension leads to higher-pitched resonance.
Reference: Exploratorium Teacher Institute (2009). The Exploratotrium Science Snackbook: cook up over 100 hands on science exhibits from everyday materials (revised edition). Robert J. Semper: United States of America. 

Tuesday, October 14, 2014

PET Bottle Membranophone

The PET (Polyethylene terephthalate, the plastic found in most platic bottles) bottle Membranophone is fun to make and even more fun to play. Using simple materials like a clean empty plastic bottle, a balloon, a rubber band, a straw, and A4 size paper we can make and play with one. This instrument produces sound from a vibrating stretched membrane or balloon.
 How to make:
Get a PET bottle and measure down about 3 inches (7.5 cm) from the top of the bottle. Using scissors, cut along the measured line. Make sure you cut evenly along the edge. Trim off any bumpy spots and recycle the bottom of the bottle. You will need the top half of the bottle to work with. Take out a punching machine and punch a hole near the cut edge of the top half bottle as far as you can get it. Put the straw through the hole to test it for size. It should be a tight fit. If the hole isn’t large enough for the diameter of the straw, re-punch in nearly the same spot to widen the hole a bit. Cut the neck off the balloon to form a sheet of elastic material- a membrane. Stretch the membrane over the hand cut opening of the bottle, making sure that the hole you punched in the side does not get hidden by excess material. Attach the membrane to the bottle with a rubber band. Wrap the rubber band around the bottle several times, making sure that the membrane is taut. Twist the cap off the bottle and set it aside. Roll a piece of A4 size paper into a tube, making it as tight and straight as possible. Put the rolled up tube into the neck of the bottle, where the cap had been. Let go of the tube when it barely touches the bottom of the membrane. It should fit securely in the hole. Tape it to the neck of the bottle so it stays in place. Insert the straw into the punched hole on the side of the bottle, and you’re ready to play.
Now that your instrument is ready, simply blow into the straw on the side of the bottle and your pet bottle Membranophone should play.

What’s going on?
As you blow into the straw, you create pressure in the space between the outer wall of the paper tube and the inner wall of the water bottle. That pressure forces the membrane to rise, allowing air to flow into the top of the tube and escape out the bottom.
As the air escapes, the membrane returns to its position. But as you continue blowing air into the instrument, you force the membrane to rapidly rise and fall, over and over again. If you place your finger over the top of the membrane, you can feel it vibrate. These vibrations produce sound.  


Tuesday, October 7, 2014

The sound and straw

By cutting the two lips of a soda straw, flattening the end, and blowing with just the right pressure, we can make sounds vibrate in the straw.
Flatten one end of the straw by sticking the end in the mouth, biting down with teeth, and pulling it out. Do this for several times to make flexible, flat-ended straw. Cut equal pieces from each side of the flat-ended so that straw has two lips at the end. Put the straw in your mouth and blow into the straw. You will probably have to experiment with blowing harder and softer while biting down with different amounts of pressure until you make the straw sing.
The monks here at CGI make straw reeds in same way to use it with Gyaling. Gyaling literally means "Indian trumpet" and is used during the monastery puja (chanting and prayer) and is associated with peaceful deities. All the monks know how to make and use this simple straw reed. Normally when they make them the reeds are shorter in length and can produce high pitch sounds. The reed goes on top of the Gyaling to make it sing.
So, the question we asked our class was ‘’What makes the straw reed produce sound?’’ To this question, the 20 students have responded with a few one-word guesses- air, pressure, vibration, high, low, hole etc. They were some pretty exciting responses. In fact, all the words that can explain the working of the straw reeds were spoken by them.
With supporting responses from the students, it was quite convenient for me to discuss the working of the reeds- when we blow through the straw, there is high pressure in your mouth. As air rushes through the straw, the pressure in the straw drops, and the high pressure outside the straw pushes the sides of the reed inward, closing off the flow. The pressure then builds inside the straw and pops the reed open again. This causes the vibration of the straw lips. When the reed vibrates at just the right frequency, there we hear loud, buzzing notes.

This is not only a good lesson on acoustic physics but also a fun way to reuse a straw.

Monday, September 29, 2014


With the end of the blessed rainy day and the beginning of the early days of the eight month of the lunar calendar, a few students have sown some more seeds in their gardens- such as bean, coriander, radish, spinach and lettuce.
The continuous rain water from the last few days has nurtured the soil making it favorable for seed’s growth, in this young season- FALL!
This time of  year is good for sowing spinach, bean, coriander, radish etc. For some vegetables we weren’t quit sure of the perfect time to plant - like egg plant, pumpkin etc- but we have decided to experiment with their growth in our garden by planting them now.
Working in the garden is a great opportunity for the students to learn with their hands. Right from the start of the garden work- digging an earth, holding a spade and pick axe and manually using one’s energy to unfurl the soil- there are many lessons being learned and many calculations being done mentally, but unconsciously.
The student’s decision to use a pick axe instead of  spade to open the soil has its own science behind it. The students are their own architects in the garden, shaping their own beds, calculating, measuring, and designing them in whatever way they desire. The depth, width and the line that they keep track of while sowing seeds are an estimation and math concept in themselves.
While there are so many things students can learn from the garden classes, the focus  in the last session was on finding an area and perimeter of their own beds. The students have used measuring tape to find the length and breadth of the beds. After they have collected their respective bed’s basic data they were ready to calculate and found the actual area of their beds. It was quite interesting to see the students measure and take their own responsibilities in their learning by doing from the context. I have also seen them cooperate with friends in finding the measurements.
From the previous planting we have now green sprouts of bean and squash that have grown from six to eight centimeters tall from the ground. The spinach and coriander have sprouted a centimeter above the bed, exposing their two leaves of early growth, ready for photosynthesis.

We all are waiting to see the gradual growth of our vegetables.

Wednesday, September 24, 2014

Sowing the seed

A squash sprout
It’s late in the seventh month of the lunar calendar, and Tshering Phuntsho, Pema Dorji and Leki Dorji have sown bean, spinach, and squash seeds in their gardens to experiment with the growth of different vegetables. 
The sowing of the seeds was accompanied by question marks in their head about the right time for planting in Dewathang. A few students have said that the sowing season in Dewathang is after the celebration of the Blessed Rainy Day or sometime in the eighth month of  the lunar calendar. However, we have decided to sow the seeds and check their growth. After three days of sowing seeds, we have checked the garden and to our excitement we found fresh squash, bean and spinach sprouts emerging out from the soil.
There are hopes from our students that these vegetables will grow, nevertheless rainy season in Dewathang is not yet completely stopped. Some students are concerned about the last heavy rain for the summer yet to fall, which would hamper the new vegetable sprouts in their gardens.
Samdrup Tshering and Leki Dorji transplanting cabbage sprouts.
On the other hand Leki Dorji and Samdrup Tshering have transplanted their cabbage sprouts in their beds. They have brought two bunches of the sprouts from the neighbor’s to plant in their gardens. Both of them were quite positive with their transplantings and were looking forward to productive growth. 
A bean sprout
Karma Phunstho has sown the lettuce seeds in his small bed and he was confident that his lettuce growth will be successful. A few students are willing to wait for the last heavy rain to go away before they sow their seeds and they are working to extend and add more new beds.

Karma Phuntsho's Lettuce garden 

Saturday, September 13, 2014

The calculator on the finger tips- Math trick

There is very convenient Math Trick to easily multiply the numbers from 6 to 10 using ones own fingers. We call this, calculator on the finger tip. It is used to teach children to learn tricks about multiplication time tables without any external resources. It also provides our students an opportunity to perfect it, anywhere and anytime just playing with their fingers after learning the trick.  
After teaching this trick in the class, most of the students who have struggled to memorize the times tables before, have admitted it to be very easy for them to calculate. It was amazing to see how handy the fingers are to calculate, besides providing mental calculation opportunity for an individual.
I remember how my students struggled to memorize the times table, especially starting from 6 to 9.  For some, they even took so long to memorize up to 5. Besides, it was of less practical memorizing, when there are gaps of few weeks and few months. The students keep on forgetting and they have to rememorize again (however not so difficult this time).    
So, in the following paragraph I am going to show you the trick. Well, first put your both hands in front of you and ascribe values from 6 to 10 to each finger starting from little finger to thumb. So, the values of  little fingers are 6, 7 for ring fingers, 8 for middle fingers, 9 for forefingers and 10 for thumbs.
How to multiply?
Step 1: Choose the numbers to multiply. For Example: 7x8   
Ste      2: Put together the fingers, whose values you want to multiply. Here, it is ring finger of the left hand and middle finger of the right hand.
Step 3: Now, count the touching fingers and the ones below them. Each of this finger will have the value of 10. So, if there are 5 fingers then the values are five times ten (5*10), which is equal to 50. Mentally retain this number in your head. 
Step 4: Now, multiply the fingers above the ones touching fingers. So, multiply 3 on left hand side with 2 on right hand side. We will get (3*2) 6.
Now mentally add 50 and 6 (50+6), the answer will be 56.
We can use this trick to calculate the times table of 6, 7, 8, 9 and 10, what amongst are the most difficult to calculate and memorize for almost all the students.

Tuesday, September 9, 2014


On last two Saturdays, our twenty students were drenched in sweat to make a vegetable garden and compost pit beside the residence of Drubgyud Tenzin Rinpoche. Rinpoche was very kind to offer his garden to the class as a learning space for the students. The continued monsoon rain in Dewathang has loosened the soil and it was quite easy for us to dig the earth. So far we have dug 20 small beds and we are getting set to sow seeds in a few weeks of time.
It’s been quite some time, waiting for a bright and dry day to begin work in the new vegetable garden. We will be experimenting in the garden with growing different seeds that are locally grown in Dewathang and also few other seeds from other place.
It was quite surprising for us to come up with long list of vegetables that can be grown in Dewathang: potato, eggplant, coriander, spinach, bean, pumpkin, squash, spring onion, cabbage, cauliflower, ginger, cucumber, tomato, radish, carrot, turnip, lettuce, etc. The list goes on. There are abundant vegetables we can grow in our garden.  
We also discussed about the right time to sow seeds in Dewathang. Students have pointed out that the summer season is usually not a good time for sowing seeds because of heavy rain fall. A few of them said we can sow seeds after blessed rainy day (which falls sometime in late September). Tshering Samdrup, a student from our class has called his parents, to ask about sowing seasons and few others have enquired to villagers. I'm happy to see how they take their responsibilities in learning.
It was quite a challenging for all of us, especially to make a bed on steep slope and leveling it, however with joined effort and cooperation we could managed to make the beds. The students have used unwanted logs and planks to make a supporting wall for the beds and to make it hold in a position they have used strong pegs.

Now, jointly we have agreed to sow seeds after the blessed rainy day. The beds are yet to finalize this weekend.