Outer hair cells sit where basilar membrane vibration is greatest

Evidence

The function of the outer hair cells is less well known, but they do not transmit information to the brain because they are connected to neurons that send information from the brain. It is believed that the outer hair cells affect the way the basilar membrane vibrates such that there is local amplification of the movement when that place is being stimulated acoustically. When they are stimulated via the neurons from the brain, it has been shown that the length of the outer hair stereocilia change (Hakizimana et al., 2012). This has the effect of mechanically amplifying the basilar membrane response within an auditory filter. Plack (2005) suggests that this amplifies frequencies perhaps half an octave above the center frequency of the auditory filter, rather like “pushing a swing at the right time” (p. 97), and that the amplification “maximum gain may be about 50 dB, but it is not the same for all levels” (p. 98). — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 561

Categorization

• XREF: The active cochlear amplifier connects to the general theme of why the ear is not a passive receiver; links to later material on nonlinearity and loudness perception. — connects to: Efferent stimulation maximally suppresses basilar membrane vibration near the characteristic frequency; Outer hair cell loss reduces hearing sensitivity by up to 60 dB — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 228
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 561