Vibrating columns of air associated with wind instruments are seldom simple or even single. In a typical instrument, especially of the “reed” or “brass” classification, besides the air column that is usually considered, there is a second column or cavity on the air supply side of the “check‐valve” or member which by opening and closing, releases air intermittently from bellows or lungs. This check‐valve may be recognized as reed, tongue, lips, membranes or vocal cords. This air‐column or cavity back of the check‐valve has some control over the time of vibration, as was demonstrated by the author at Cleveland meeting of the Society, December 1st, 1931.
Usually the vibrations of the supply‐side air column are heard not at all or but faintly, because of restricted opportunity for sound emission. But special devices may be employed (the stethoscope is an example) to hear sound in supply side air column and reduce or effectively suppress sound from external air column (the only one ordinarily considered).
With a microphone in close contact with an individual's chest, an amplifier and loudspeaker will make audible the sounds picked up from internal air column, and with sufficient amplification, the normal sounds of speech and singing are faint in comparison with the other. This set‐up demonstrates that while the individual has pitch control on vibrations of the internal air column, he does not and cannot change the character or quality of the supply‐side tone by any of the vocal speech or musical efforts.
This result is taken to indicate that the vocal cords have but one mode of opening and dosing (at a given pitch) and play no part in determining the character or quality of vowels and other “vocalized” sounds.