The Flow

Weekly Teaching Tip – January 11, 2016
by Dr. Curt Stock, MD

Several years ago as I was introduced to the World of Voice and Singing. I was bombarded with terms like Chest and Head voice which to a scientific mind were totally foreign. I heard terms like passaggio, breath support, Harmonics and Formants. I set out on a quest to understand these terms and for the most part through personal study, conferences and mentors like Hubert Noe MD, Dean Kaelin (Maestro) , Don Miller PhD, Anna Siciliano SLP and Teri Stock (CFO and CEO of the Stock family and voice teacher extraordinare) I have gained a fairly decent understanding of these concepts. The most enigmatic term however is breath support. I have read and reviewed many articles and heard most recently discussions on this subject and feel I am achieving a basic understanding on this subject. Terms like Bel Canto, Appogiarsi, Cantare sul fiato and Flow phonation have a definite meaning even though I am not an accomplished singer. Here is my take on this complex subject.

Intuitively and scientifically I understand that increasing pressure with the abdomen without adjusting the vocal folds is damaging to the vocal fold mucosa through increased pressure. Imbalance of the pressure to the valve is counterproductive. The human abdominal muscles produce 200 watts of energy as opposed to 2 watts created by the vocal folds, giving the vocal folds an unfair disadvantage. Certain principles apply, for every reaction there is an equal and opposite reaction, also energy is not created or destroyed, just manipulated. Hence this energy created from the respiratory tract needs to be manipulated in order to not damage vocal fold mucosa. It is manipulated by the glottis in concert with a consistent air pressure from below. The constant airflow needs to be sufficient to set the vocal folds in motion with proper undulation and needs to be constant as the notes are sung, both in chest and head. This is accomplished by the glottis (Cricothyroid and Thyroarytenoid muscles) and lower respiratory tract working in opposition and in concert.

To better understand this relationship we need to review some basic Laws and Principles of Physics. The Bernoulli principle; Hydrodynamica 1738 . Fluids and gases moving faster than the surrounding area possess lower pressures. An example of this is an airplane wing; the air flowing over the wing moves faster and therefore there is less pressure than the air going under the wing which causes lift. This conforms with Newtons 2nd Law which states if a fluid is moving from an area of high pressure to lower pressure, then there is more pressure behind than in front. This principle is used in carburaters where gas is pushed through a smaller tube from high pressure to a lower pressure. This produces a net force on the volume (air or Liquid) which accelerates it along in a streamline. The highest speed occurs where there is less pressure. This brings us to another interesting law that comes into play. Boyles law states that pressure and volume have an inverse relationship as long as temperature is held constant. Gases moving from a wider pipe into a narrower pipe accelerate and the volume of the gas moving a given distance in a given time does not change. To achieve this the fluid or gas must move faster. An example of this is a river as it flows from wider to narrower channels. The amount of water passing along the channel remains at a constant volume. This means the pressure and speed change but the volume is constant, if not the river would back up, like placing a dam in the middle. The energy of the fluid must also remain the same. This energy switches back and forth from static to kinetic energy , but the total energy remains the same.

So what does all this have to do with flow? I have talked about laws of gases and fluids, but only where they apply to both. As we generate air volume and pressure from the lower respiratory tract there is greater pressure in the larger trachea. As the air flows upward, the trachea narrows into a conical passage called the subglottis and finally comes into contact with the vocal folds. Remember there is less pressure in the narrower glottic opening and the air accelerates through the vocal folds. This opening is controlled with the CT and TA muscles. As the air flows past the vocal folds it causes them to undulate from the bottom surface to the top and creates the Vertical Phase Difference. If the glottic valve is narrowed the air moves faster and the voice goes higher and with the vocal folds stretching tighter and vibrating faster with the air pressure holding constant by the accomplished singer. Remember the volume of air coming from the lower respiratory tract has to be equal to the volume of the air going through the narrowing glottis so it has to accelerate or damming affect will occur. If the air pressure is increased too forcefully, this air pressure cannot flow through the glottis and causes damage to the vocal folds and mucosa. Therefore, the vocal folds have to be the controller and the airway pressure needs to be constant or at least titrated slowly to accommodate the change in the area of the glottal valve and rate of the gas (air) passing through this valve.

Curt R Stock MD

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