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Summary: The Auditory System

The ear responds to pressure waves in the air gathered by the outer ear and directed down the auditory canal to the tympanic membrane or eardrum. Movements of the eardrum are amplified by a chain of three tiny bones in the middle ear: the ossicles.

The cochlea of the inner ear is the part of the auditory system responsible for transduction (conversion of energy from one form to another). Before doing transduction, the cochlea converts movements of the oval window into standing waves along the cochlear membranes.

Hair-like cells along the cochlear membranes respond to movement by producing electrical potentials. Ultimately these stimulate nerve impulses sent to the brain along the auditory nerve. Normal adults hear frequencies from about 50-15,000 Hz.

Vibrations below 50 Hz can sometimes be felt as pressures waves, and vibrations from 15-20,000 may be heard by young people or detected in music as greater "presence."

Sensory hallucinations can be quite vivid and realistic. They occur in all the senses. When people lose normal input to sensory cortex due to accident or old age, the brain tissue may grow irritable and generate its own activity.

Normal perception is also a construction, but normal perception is constrained and guided by the sensory input. That is how our perceptual systems produce results dependable and accurate enough to be treated as veridical or faithful to reality.

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