title: Low-frequency sound affects active micromechanics in the human inner ear.
abstract: Noise-induced hearing loss is one of the most common auditory pathologies, resulting from overstimulation of the human cochlea, an exquisitely sensitive micromechanical device. At very low frequencies (less than 250 Hz), however, the sensitivity of human hearing, and therefore the perceived loudness is poor. The perceived loudness is mediated by the inner hair cells of the cochlea which are driven very inadequately at low frequencies. To assess the impact of low-frequency (LF) sound, we exploited a by-product of the active amplification of sound outer hair cells (OHCs) perform, so-called spontaneous otoacoustic emissions. These are faint sounds produced by the inner ear that can be used to detect changes of cochlear physiology. We show that a short exposure to perceptually unobtrusive, LF sounds significantly affects OHCs: a 90 s, 80 dB(A) LF sound induced slow, concordant and positively correlated frequency and level oscillations of spontaneous otoacoustic emissions that lasted for about 2 min after LF sound offset. LF sounds, contrary to their unobtrusive perception, strongly stimulate the human cochlea and affect amplification processes in the most sensitive and important frequency range of human hearing.
authors.affiliation: German Center for Vertigo and Balance Disorders (IFB) , University of Munich , 81377 Munich, Germany ; Department Biology II , University of Munich , 82152 Martinsried, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Kugler
authors.affiliation: Department Biology II , University of Munich , 82152 Martinsried, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Wiegrebe
authors.affiliation: Department Biology II , University of Munich , 82152 Martinsried, Germany.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Grothe
authors.affiliation: Institute for Cell Biology and Neuroscience, Johann Wolfgang Goethe University , 60438 Frankfurt/Main, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Kössl
authors.affiliation: German Center for Vertigo and Balance Disorders (IFB) , University of Munich , 81377 Munich, Germany ; Department of Otorhinolaryngology, Head and Neck Surgery, Grosshadern Medical Centre , University of Munich , 81377 Munich, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Gürkov
authors.affiliation: German Center for Vertigo and Balance Disorders (IFB) , University of Munich , 81377 Munich, Germany ; Department of Otorhinolaryngology, Head and Neck Surgery, Grosshadern Medical Centre , University of Munich , 81377 Munich, Germany.
authors.forename: Eike
authors.initials: E
authors.lastname: Krause
authors.affiliation: German Center for Vertigo and Balance Disorders (IFB) , University of Munich , 81377 Munich, Germany ; Department of Otorhinolaryngology, Head and Neck Surgery, Grosshadern Medical Centre , University of Munich , 81377 Munich, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Drexl
keywords: cochlea; low-frequency sound; noise-induced hearing loss; spontaneous otoacoustic emissions