04/28/2026
"One way of increasing the efficiency of the vibrating system is to reduce the viscosity. But how can this be done? What control do we have over the composition of fluids in our vocal folds?
To appreciate this, consider the range of viscosities of various liquids in the body. Water has a viscosity of 0.01 poise, saliva 0.03 poise, and mucus in the respiratory tract 0.06 poise. (A poise is a standard unit of viscosity. Imagine a cubic centimeter of liquid attached to a vertical wall on one surface. If it were to sag downward under the force of gravity about one centimeter per second on the opposite free surface, its viscosity would be about one poise.)
The average viscosity on the inside of the vocal folds is more than 10 poise, much larger than the viscosity of the mucus deposited on its surface. We don’t know exactly what regulates the viscosity on the inside, whether it is the lymphatic system or the circulatory system, or whether the mucus on the outside is allowed to pe*****te through the mucous membrane (skin) to “thin out” the mucus on the inside. Whatever the case may be, it is clear that more watery substance delivered to the vocal folds, inside or outside, will lower the effective viscosity. This will minimize energy loss due to friction. "
from "An Additional Look at Vocal Fatigue: Part II" by Dr. Ingo Titze. First published in NATS Bulletin, a predecessor to the Journal of Voice. Nov/Dec. 1983
