phonation threshold pressure
After my last blog post I got a question about support and breathing so I thought I could write a bit more about it. First a disclaimer: I'm trying to balance between being specific and clear so probably I will fail miserably in both.
We all know that air flowing out of the lungs is needed for the vocal folds to start vibrating (of course you could produce sound by inhaling too but let's leave that out for now). In order to keep the vocal folds vibrating the airflow must be kept up. Phonation threshold pressure (PTP) is the minimum subglottic pressure needed to keep the vocal folds vibrating. If the pressure stays under the threshold there is no vibration. PTP is affected by the fundamental frequency and also the amount of adduction and stiffness of the vocal folds as well as the shape of the vocal tract (see eg Titze 2000).
In singing the PTP is changing constantly. So the suitable pressure to make different sounds is changing. Let’s make it a bit more simple and think what happens if we produce one long tone in one pitch without changing the quality. We need both a constant subglottic pressure and vocal fold setting. Because the air is flowing out while we sing the lung volume diminishes too. You can perceive that around chest and abdomen. Singers have been observed to have different strategies on whether the chest or the abdomen goes in first. Anyway it’s simply not possible to keep them both extended while singing a phrase. The pressure would drop too low.
It doesn’t matter much how exactly you produce the necessary pressure as long as you do it. Because singers are different there are probably many viable training strategies. There are two that I advice to avoid though. First one is trying to keep the whole torso expanded which will lead to insufficient pressure. The other one to avoid is to tense muscles suddenly. That will often lead to subglottic pressure first increasing and then decreasing which will probably have an effect on the sound quality and pitch.
Things that are utter nonsense can work as learning tools for singers. I come up with all kinds of images when I’m teaching. Often they prove to be useful. However, I always remind that they are just that, images. They don’t represent how things actually work. So even if I said earlier that you shouldn’t keep your torso expanded thinking about doing it might actually work in some cases.
While on the subject I’ll give a little critique on how support is presented in Complete Vocal Technique. Cathrine Sadolin describes support as if holding back the breath (Sadolin 2018). The idea is that after we have inhaled our lungs want to let the air out. We should work against this urge by engaging our abdominal and back muscles. I guess this could be true in theory if we would only sing until our lungs reach their resting volume. You can find your resting lung volume by inhaling and then letting your breath out with a relaxed sigh. You will find that it is possible to exhale even after that. In order to do that we need to engage our abdominal muscles. Those muscles Sadolin describes as support muscles (which would mean that according to her they hold back the breath).
I believe that the muscles of both inhalation and exhalation should work together from the beginning of a phrase so that we can better regulate the subglottic pressure. More intensive phonation and higher fundamental frequency require higher subglottic pressure. PTP is higher and vocal folds won’t vibrate if the pressure stays too low. I find it pretty logical that muscles of exhalation can assist in controlling the pressure.
So what is holding back the breath if not support muscles? That is vocal folds (adduction and stiffness I mentioned earlier). For this reason I think it’s useful to include vocal fold function when training “support”. In practice this could mean doing the same exercise several times and changing the focus between laryngeal function and support muscles.
So PTP is changing depending on the pitch and intensity. This means that also the intensity of the muscle work to produce the pressure is changing. I believe that if there is an option of achieving the artistic expression with smaller pressure change you should aim for that. I have some interesting observations about this, one from the study I did together with Johan Sundberg (Sundberg et al 2017). However, I’ll write more about them later.
This post got a bit too long as it is but I’m happy to continue discussing the subject in the comments. Next weekend I’ll be heading to London to attend the conference ‘Towards Best Practice: Teaching Singing in Higher Education’. I’m going to write a more in-depth post about it later but you can tune into my Facebook and Instagram for some real-time updates.
― Ville ―
Sadolin C. (2018). Complete Vocal Technique mobile application. Complete Vocal Institute.
Sundberg J., Holmberg A., Bitelli M., Laaksonen V. (2017). The "Overdrive" Mode in the "Complete Vocal Technique": A Preliminary Study. Journal of Voice.
Titze I. (2000). Principles of Voice Production. Iowa City: National Center for Voice and Speech.