Mechanical Filtering of Sound in the Inner Ear

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 250; no. 1327; pp. 29 - 34
• Main Authors: Brown, A. M., Gaskill, S. A., Williams, David M.
• Format: Journal Article
• Language: English
• Published: London The Royal Society 22.10.1992; Royal Society of London
• Subjects: Acoustic Stimulation; Adult; Basilar membrane; Basilar Membrane - physiology; Biological and medical sciences; Biomechanical Phenomena; Cochlea; Cochlea - physiology; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Ear canal; Ear, Inner - physiology; Female; Fracture mechanics; Frequency ranges; Fundamental and applied biological sciences. Psychology; Hearing - physiology; Humans; Male; Octaves; Outer hair cells; Perceptual Distortion - physiology; Stereocilia; Tectorial membrane; Tectorial Membrane - physiology; Tonal regions; Vertebrates: nervous system and sense organs; Human; Basilar membrane; Filtration; Acoustic stimulus; Cochlea; Sound; Mechanical filter; Tectorial membrane; Inner ear; Organ of hearing
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.1992.0126

We have studied the distortion generated by the cochlea to gain insight into the mechanisms responsible for the sharp tuning or ‘frequency selectivity’ of the inner ear. We used two stimulating tones of moderate intensity which are progressively separated in frequency, and measured the ear canal cubic distortion components which are generated as a consequence of the stimulus interaction in the cochlea. We inferred that the distortion is generated from the frequency region of the higher of the two stimulus tones and that it is then band-pass filtered by a structure which is tuned to a frequency just over half an octave below that of the high-frequency tone. We suggest that the structure responsible for this band-pass filtering is the tectorial membrane, and we conclude that our results support theories of cochlear mechanics in which resonances due to the tectorial membrane interact with those of the basilar membrane to enhance the frequency selectivity of the inner ear.