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Low-frequency sound affects active micromechanics in the human inner ear
Kathrin Kugler1, Lutz Wiegrebe2, Benedikt Grothe2
1German Center for Vertigo and Balance Disorders (IFB) , University of Munich , 81377 Munich, Germany ; Department Biology II , University of Munich , 82152 Martinsried, Germany.
Royal Society Open Science
|June 12, 2015
Summary
Low-frequency sound, though perceived as quiet, significantly impacts the cochlea. This study reveals that even brief exposure to unobtrusive low-frequency sound disrupts the amplification processes crucial for hearing.
Area of Science:
- Auditory Neuroscience
- Otoacoustic Emissions
- Human Hearing Physiology
Background:
- Noise-induced hearing loss is a common auditory pathology from cochlear overstimulation.
- Human hearing sensitivity and perceived loudness are poor at very low frequencies (<250 Hz).
- Inner hair cells inadequately driven at low frequencies limit perceived loudness.
Purpose of the Study:
- To assess the impact of low-frequency (LF) sound on cochlear physiology.
- To investigate LF sound effects using spontaneous otoacoustic emissions (SOAEs) as a marker of outer hair cell (OHC) function.
Main Methods:
- Exposure to a 90-second, 80 dB(A) LF sound stimulus.
- Monitoring of SOAEs, which reflect cochlear active amplification processes.
- Analysis of SOAE frequency and level oscillations post-exposure.
Main Results:
- A short exposure to perceptually unobtrusive LF sound significantly affected OHCs.
- LF sound induced slow, correlated oscillations in SOAE frequency and level lasting approximately 2 minutes.
- These oscillations indicate a strong stimulation of the cochlea by LF sound.
Conclusions:
- LF sounds, despite poor perception, strongly stimulate the human cochlea.
- LF sound exposure affects the active amplification processes in the cochlea's most sensitive frequency range.
- This finding has implications for understanding auditory pathologies and hearing protection.
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