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The Greenwood function correlates the position of the hair cells in the inner ear to the frequencies that stimulate their corresponding auditory neurons.Empirically derived in 1961 by Donald D. Greenwood, the relationship has shown to be constant throughout mammalian species when scaled to the appropriate cochlear spiral lengths and audible frequency ranges.
In audiology and psychoacoustics the concept of critical bands, introduced by Harvey Fletcher in 1933 [1] and refined in 1940, [2] describes the frequency bandwidth of the "auditory filter" created by the cochlea, the sense organ of hearing within the inner ear.
Human ear anatomy, with the cochlea "uncoiled" showing frequency mapping to different regions of the basilar membrane. Cross-sectional view of the organ of Corti within the cochlea. The basilar membrane is labeled "basilar fiber." The basilar membrane and the hair cells of the cochlea function as a sharply tuned frequency analyzer. [3]
Assessment of transient evoked otoacoustic emissions (TEOAE) in an adult. An otoacoustic emission (OAE) is a sound that is generated from within the inner ear.Having been predicted by Austrian astrophysicist Thomas Gold in 1948, its existence was first demonstrated experimentally by British physicist David Kemp in 1978, [1] and otoacoustic emissions have since been shown to arise through a ...
Harbour porpoises emit sounds at two bands, one at 2 kHz and one above 110 kHz. The cochlea in these dolphins is specialised to accommodate extreme high frequency sounds and is extremely narrow at the base. Type II cochlea are found primarily in offshore and open water species of whales, such as the bottlenose dolphin. The sounds produced by ...
The superior frequency range in mammals is partly due to their unique mechanism of pre-amplification of sound by active cell-body vibrations of outer hair cells. Frequency resolution is, however, not better in mammals than in most lizards and birds, but the upper frequency limit is – sometimes much – higher.
Three methods are traditionally used for testing a subject's perception of a stimulus: the method of limits, the method of constant stimuli, and the method of adjustment. [4] Series of descending and ascending runs in Method of Limits Method of limits In the method of limits, the tester controls the level of the stimuli.
This pressure wave travels along the BM of the cochlea until it reaches an area that corresponds to its maximum vibration frequency; this is then coded as pitch. [13] High frequency sounds stimulate neurons at the base of the structure and lower frequency sounds stimulate neurons at the apex. [13] This represents cochlear tonotopic organization.