Since the human voice will be the main subject of this blog we might as well ask ourselves: What ís the human voices, and how does it come into being ?

I think we can say that if we “use our voices” we create sound. And sound is: vibrations that travel through the air (or another medium) and are processed by the ear and perceived by the brains as a sound ‘sensation’.

How can we, humans, create these air vibrations to make “voice” ?

I will try to explain it simple. If you want to know more details, I can recommend some nice books…but maybe you don’t need too much detail to understand a little bit better what our body, our instrument, needs to do to make “voice”. Still, you may want to read the following text another two times before you get the picture… 🙂

When we want to make a sound with our voice, our brains will give orders to certain muscles to start a complicated process in our body.

The brain will give orders to muscles situated in the larynx, to close the vocal folds firmly. We call this the process of adduction of the vocal folds. At the same time, muscles that control our breath get the order to increase the air pressure in the lungs. The most important breath-muscle is the diaphragm that will start to move a little bit upwards. This reduces the volume of the lungs and as the air cannot escape (because the vocal folds are closed…), the pressure in our lungs, or more correctly: the pressure under our vocal folds known as the “sub-glottal pressure” will increase. This refers to the “glottis”, the name for the opening between the vocal folds.
At some moment the air pressure becomes so high that the vocal folds are blown open because the muscles of adduction cannot resist the air pressure anymore. When the vocal folds open, air can escape and flows through the folds. 

And then, there is a law of physics (Bernouilli’s law) that says that when air is flowing, its pressure is reduced (!). As a consequence, the adduction forces in the vocal folds become stronger than the air pressure and the folds close again. As soon as they are closed, the air-pressure in the lungs (the sub-glottal pressure) builds up again and rapidly opens the vocal folds… 

This process of opening and closing the vocal folds is repeated over and over again and creates a tone with some frequency, the number of times the process of opening and closing is repeated in a second. So, if we sing on a A4 we create a vibration in which the vocal folds open and close 440 times a second (440 Herz). Just imagine how fast that is ! 

Hmm…not an easy subject…right ? 

let’s take another example of the law of Bernouilli: When you think of a train that passes in a railway station very fast…did you ever experience that you felt drawn towards that train ? It is because of the fast moving air and the reduction of its pressure that you were drawn towards the train…

The muscles that control our breath (diaphragm and intercostals) and the muscles of adduction create together the sub-glottal air-pressure we need to blow open our vocal folds. And especially the diaphragm creates this constantly maintained airflow we need for the law of Bernouilli. 

If we want to come to grips with the process of creating the human voice we need to train all those muscles mentioned above to do a proper and well co-ordinated job…

This isn’t an easy subject so… if you have any questions or remarks…please send me a message !!


11 antwoorden
    • Lieve Geuens
      Lieve Geuens zegt:

      …thank you dear Esther…I will do my best but I am very happy that I am surrounded by good books and people who know about the voice like Gerrit Bloothooft. When I am not sure about something I will ask them for advice.

  1. Fuensanta
    Fuensanta zegt:

    Very interesting, I didn’t know this!
    If an A4 is 440 ‘fold openings’, what’s the relation between air pressure/tilting of the larynx/activity (firmness) of the glottal muscles/frequency of fold openings and pitch?
    It’s not very clear to me, maybe you have some ideas?


    • Lieve Geuens
      Lieve Geuens zegt:

      Dear Fuen, Welcome !! That are some good questions !
      Very soon I will publish an article of Gerrit Bloothooft where he will talk about this !! I will send you a mail when I can place it in my blog.

      But to give already a clue:
      The higher the sub glottal air pressure is, the harder the muscles of adduction have to work to keep the vocal folds closed.
      When will you increase the sub glottal pressure ? First: when you want to sing louder, and second: when you want to sing a note on a higher pitch.

      When you want to sing louder, and you increase the sub glottal pressure and the muscles of adduction work harder, the vocal folds will be closed with more “mass” and will be closed longer. This gives a louder sound.
      When you want to sing in a higher pitch in modal (or mode 1/ chestvoice/ not tilted) the musculus vocalis in your vocal folds will become more tight. Therefore the vocal fold will vibrate faster (which gives a higher pitch). But to make a vocal fold vibrate that is tighter you will need a higher air pressure… do you get this?
      When you are in falset (or mode2/headvoice/tilt) the thyroid cartilage will come down and stretch the vocal folds so you can sing even higher : as I already said: the tighter (and in this case also thinner) the vocal folds are the faster they will vibrate. Just think of tuning your double bass: when you want the string to be in a higher pitch you will stretch the string more….
      (I didn’t mention the mixed voice: I will write something about that in another post…)

      So the muscles in your vocal folds (musculis vocalis) that can stretch your vocal cords, and the crico-thyroid muscles that can make the thyroid tilt are responsible for the pitch you sing in.

      If you sing an A1 (or international A4) your vocal folds will vibrate 440 times a second (=Herz) , just as the strings on your double bass or in the acoustic piano will do. When you sing an (International) A5 they will vibrate twice as fast: 880 times a second. A3 is 220 Herz; the strings or vocal folds will vibrate 220 times a second.

      Did I answer your questions ? If not….ask again ! X

  2. Fuensanta
    Fuensanta zegt:

    I think it’s clear, thank you for your great response! I’m looking forward to that article also and the piece on mixed voice.


  3. Ingrid Smeenk
    Ingrid Smeenk zegt:

    Dear Lieve ,

    I have read the information a few times . It ’s complicated for me but I understand your article as you ve explained it in a very clear manner.
    So about the Bernoulli effect if I understand correctly ,the higher the sub glottal pressure the harder the vocal cords/muscles have to work to get closure before they are blown open again in the opening closing cycle to make sound or they open for breathing.
    So you need more mass for heavier closure of the vocal folds (the adductor muscles need to work harder for closure with more mass)This gives a louder volume sound.(Modal,mode 1 ,chest voice)
    Than when you want to sing in falset (Tilt,Headvoice ,mode 2) you need also more sub glottal pressure for the vocal cords muscles to lengthen (stretch)and tighten . I am trying this now with two elastic bands so I can make it visual for myself.
    So in Falset the thyroid comes forward a little bit and the larynx goes up and than to get good closure tp prevent the folds from opening you don t need the mass as you want the cords to stretch and tighten and thin, but also for that you need the same sub glottal pressure ? Did I understand this correctly ?

    • Lieve Geuens
      Lieve Geuens zegt:

      Dear Ingrid, welcome again ! 🙂
      Yes, the 3 little groups that make your vocal chords close will have to work harder when the sub glottal pressure increases.
      I am not sure if I understand your second question right but you will have a louder voice when the vocal chords are closed for a longer period. When there is more mass involved it is easier to have a longer closure of the vocal chords.
      It is not the sub glottal pressure that lengthens your vocal chords in mode 2 but (as you write) the tilting of the Thyroid cartilage. The larynx does not have to go up: classical singers will keep the larynx in quite a low position. Non-classical singers will often lift the larynx in higher notes.
      The higher the note, the more glottal pressure you need:
      In mode 1 the vocal chords will have more tension in higher notes because the musculus vocalis will tighten. The higher the note, the more the musculus vocalis will tighten. In mode 2 the vocal chords will be lengthened by the tilting of the Thyroid cartilage.

      And now scientists are talking about the idea that there is something like a mixed voice in which probably the musculus vocalis is working while the Thyroid cartilage is already tilting…

      Did I give answers to your questions ?


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