The Hearing Process
Ears are sensitive instruments that detect the mechanical forces of sound waves. These sound waves are picked up by the pinna, the visible part of the ear, transferred into the external ear canal, and sent into the cochlea where stereocilia, also known as hair cells, trigger neurotransmitters along the auditory nerve. The brain receives the stimulation, reconstructs the information, interprets the sound recognition, conducts a speech analysis, and determines directional awareness if the sound occurs from behind (Brownell, 1997).
Sound waves are described in decibels (dBs), which provide a measure of the volume of sound, and in hertz (Hz), which provide a measure of the frequency or pitch of the sound. Audible volumes for humans range from zero to ten dBs as in soft breathing; from 50 to 60 dBs as in normal conversation, to more than 110 dBs, a volume loud enough to elicit pain (Noise Sources and their Effects, n.d.). Humans can hear frequencies between 20 Hz (low vibrations) up to 20,000 Hz (Cutnell & Johnson, 1998).