Key ideas

• Sound waves are created when a vibrating object pushes nearby air molecules, creating a wave pattern that travels through the air.
• A sound wave's frequency determines its pitch, while its amplitude determines its loudness.
• Sound waves vibrate the eardrum, pass through three tiny middle-ear bones into the cochlea, where hair cells transduce the vibrations into neural signals.
• The brain localizes sound by comparing the tiny differences in when and how loudly a sound reaches each ear.
• Conduction deafness means sound can't get in through the outer or middle ear; sensorineural deafness means sound gets in but the inner ear can't send the signal.

Key terms

sound wave

A wave pattern of moving air molecules created by a vibrating object.

frequency

How quickly a sound wave repeats each second; it determines pitch (higher frequency = higher pitch).

pitch

How high or low a sound is heard, determined by the wave's frequency.

amplitude

The strength or intensity of a sound wave; greater amplitude is heard as louder.

eardrum

The structure that vibrates when sound waves enter the ear.

cochlea

The inner-ear structure where hair cells transduce vibrations into neural signals.

hair cells

Tiny receptor cells in the cochlea that transduce sound vibrations into neural signals.

sound localization

The brain's ability to determine where a sound came from by comparing timing and loudness at each ear.

conduction deafness

Hearing loss from a problem conducting sound through the outer or middle ear, such as an eardrum that doesn't vibrate properly.

sensorineural deafness

Hearing loss from damage to inner-ear structures, such as cochlear hair cells, often from aging or loud sounds.

Watch out