Sound. Sound, the stimulus for
hearing, is made up of a series of pressures, usually of air, that can be represented as waves.
Sound waves have three characteristics—amplitude, frequency, and purity—each of which is related to a psychological experience. Greater wave
amplitudes are related to greater
loudness; wave frequency is related to
pitch; and
wave purity is related to
timbre.
The hearing system. The
outer ear, the
pinna, collects sound waves and funnels them through the
auditory canal to the
eardrum (which separates the outer and middle ears) and causes it to vibrate. (See Figure
1 .) The
middle ear contains the
malleus (hammer), incus (anvil), and
stapes (stirrup), which move and transmit the sound to the
oval window, which separates the middle ear from the inner ear. Beyond the oval window is the
inner ear, whose main structure is the
cochlea, a snail-like structure that has a membrane, the
basilar membrane, stretched along its length. When the stapes vibrates against the oval window, the fluid in the cochlea moves and causes the basilar membrane to vibrate. The receptors for hearing, the
hair cells, lie in the basilar membrane and convert the vibrations into
neural impulses. The neural impulses, in turn, move along the
auditory nerve to the lower
brain stem and then ascend to the auditory part of the
thalamus and on to the
auditory cortex in the temporal lobe. Input from each ear is received on both sides of the brain.
Psychology: Measurement and Statistics
Psychology: Sensation
