Acoustics

Abstract

The voice starts with the so-called vocal cords. These organs are in the form of a double reed: in effect a pair of lips, not unlike the lips of the human mouth. The edges can be brought together, and air from the lungs can be forced through between them. They will then be set in vibration and will produce a periodic interruption of the air blast, much as do the lips of a bugler or cornet player. The pitch of the note produced depends on the thickness, tension, and vibrating length of the two cords, factors that can be varied. The two cords lie in the same horizontal plane and run from front to back. They open widely during the act of breathing, and are about three-quarters of an inch long in the case of men, about half an inch in the case of women. The “cracking” of the adolescent boy’s voice is due to a comparatively rapid change in the length of the cords to about twice the previous value. The male speaking voice has an average fundamental frequency of about 145 cycles sec^-1, female 230, each with a range of about two octaves (i.e., a factor 4). The lowest frequency of a cathedral-choir bass is about 66 cycles sec^-1, the highest fundamental of a soprano about 1056. (There are exceptions going as much as an octave higher.)