ligaments in the larynx. The vocal
cords in man are actuated by the air from the lungs. The size and
tension of the vocal cords and the volume and the velocity of the air
from the lungs control the tones of the voice. The more tightly the
vocal cords be drawn, other things being equal, the higher will be the
pitch of the sound; that is, the higher the frequency of vibration
produced by the voice. The pitches of the human voice lie, in general,
between the frequencies of 87 and 768 per second. These are the
extremes of pitch, and it is not to be understood that any such range
of pitch is utilized in ordinary speech. An average man speaks mostly
between the fundamental frequencies of 85 and 160 per second. Many
female speaking voices use fundamental frequencies between 150 and 320
vibrations per second. It is obvious from what has been said that in
all cases these speaking fundamentals are accompanied by their
multiples, giving complexity to the resulting wave-trains and
character to the speaking voice.

Speech-sounds result from shocks given to the air by the organs of
speech; these organs are principally the mouth cavity, the tongue, and
the teeth. The vocal cords are _voice-organs_; that is, man only truly
speaks, yet the lower animals have voice. Speech may be whispered,
using no voice. Note the distinction between speech and voice, and the
organs of both.

The speech of adults has a mean pitch lower than that of children; of
adult males, lower than that of females.

There is no close analogue for the voice-organ in artificial
mechanism, but the use of the lips in playing a bugle, trumpet,
cornet, or trombone is a fairly close one. Here the lips, in contact
with each other, are stretched across one end of a tube (the
mouthpiece) while the air is blown between the lips by the lungs. A
musical tone results; if the instrument be a bugle or a trumpet of
fixed tube length, the pitch will be some one of several certain
tones, depending on the tension on the lips. The loudness depends on
the force of the blast of air; the character depends largely on the
bugle.

Human Ear. The human ear, the organ of hearing in man, is a complex
mechanism of three general parts, relative to sound waves: a
wave-collecting part; a wave-observing part, and a wave-interpreting
part.

The outer ear collects and reflects the waves inwardly to beat upon
the tympanum, or ear drum, a membrane diaphragm. The uses of the rolls
or convolutions o