I belong to a Voice Geek Forum on Facebook and recently there was talk about how to make belting safe. One member Ken Bozeman posted a brilliant comment that really struck me. Here it is below –
What I am saying these days is, that it is not the subglottal pressure alone that determines the risk–it is the transglottal pressure difference, that is, the difference in pressure from below to above the glottis.That is the pressure load that the glottal resistance is bearing/resisting.The greater that load (difference) the harder the folds have to press together, the more likely the build up of tissue inflammation and damage.The way to keep it comfy is to find acoustic strategies that raise the supra-glottic pressure along with the higher sub-glottic pressure, so the difference is kept manageable. The other thing I think (opine) is that while sufficient airflow is needed, air blast is not helpful.Getting efficient glottal closure with a relatively clean glottal signal is safer.I suspect that for genres using distortion, other structures in the area (false folds, arytenoids)work better, but since I am not a specialist in those sounds, I would defer to them on that.
The glottis is the space between the vocal folds, so really just the vocal folds themselves. What he is saying is basically that the difference in air pressure from below the vocal folds to above is what determines the risk! The major take away is that you can’t blow air. You have to create pressure from above that goes back on to the vocal folds. So how does one increase Supra Glottic pressure (above vocal fold pressure)? What are these acoustic strategies? The belt sound itself is one great way to increase supra glottic pressure. The sound itself is an acoustic strategy. Other ways is to increase ring or twang in the sound. Ring in the voice creates pressure back onto the vocal folds allowing you to be louder for less effort! Another great way is to use Semi – Occluded Vocal Tract Exercises (SOVT – partially closed mouth). These exercises as well create pressure back onto to the vocal folds. Here is one of my videos on SOVT exercises.
Here’s a video on Belt Vowels you can try!