The human ear serves two major special sensory functions--hearing (auditory) and equilibrium (balance). The stimulus for hearing is sound waves. The stimulus for equilibrium is gravitational forces.

a. Methods of Sound Transmission. The sound stimulus is transmitted in a variety of ways. Regardless of the actual transmission method, the sound stimulus is unchanged. Sound may be transmitted as:

(1) Airborne waves. These airborne waves have frequency (pitch) and amplitude (loudness or intensity).

(2) Mechanical oscillations (vibrations) of structures.

(3) Fluid-borne pressure pulses.

(4) Electrical impulses along the neurons to and in the brain.

b. Sections of the Human Ear (figure 11-12). The human ear has three major parts. Each part serves a specific function in the transmission and reception of the sound stimulus. The three parts are known as the external (outer) ear, the middle ear, and the internal (inner) ear.

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