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Frequency Selectivity and Nonlinearity in Hearing
Discover how the inner ear analyzes frequency, generates its own phantom tones, and suffers permanent damage from the noise of modern life.
Lecture guide · Written by AI from the lecture. For the lecture’s own words, open the Transcript tab.
Examines the mechanical properties of the inner ear that govern frequency selectivity and nonlinear auditory responses. Josh McDermott explains how behavioral masking experiments and notched-noise methods allow researchers to infer human filter bandwidths, and details the level-dependent amplification provided by outer hair cells that generates a compressive response function and aural distortion products. Finally, the session explores hearing loss, contrasting conductive and sensorineural impairments, reviewing otopathological evidence of age-related hair cell loss, and discussing the impact of noise exposure.
This lecture assumes
- Neural Networkstaught in Artificial Intelligence at 43:38
Key Takeaways
- The cochlea functions as a bank of bandpass filters whose frequency selectivity can be indirectly measured using masking techniques.
- Outer hair cells act as a level-dependent amplifier that boosts low-intensity sounds and produces sharp tuning curves at low sound levels.
- Nonlinearities in the inner ear create a compressive response function and give rise to measurable aural distortion products and combination tones.
- Hearing loss is divided into conductive losses affecting mechanical transmission and sensorineural losses involving inner ear transduction.
Concepts Explained21
Inner hair cells—The sensory receptors in the cochlea that move in response to sound and transduce mechanical energy into a voltage change.
Outer hair cells—Receptor cells that change shape in response to electrical signals.
Characteristic frequency—The special frequency to which an auditory nerve fiber responds best with the lowest sound intensity threshold.
Beating—An acoustic phenomenon that occurs when multiple frequencies are present, resulting in a waxing and waning in amplitude.
Examples, Proofs & Derivations
Works & Sources Cited22
Primary Document
American Standards Association, 1960—Definition of masking cited on the slide.
Paper
Egan and Hake (1950)—Masking of a target pure tone graph
Paper
Moore et al. (1993)—Data for threshold of a 2 kHz sinusoidal signal plotted as a function of a noise masker
Paper
Critical bands—Fletcher, 1940, cited for measuring frequency selectivity by masking.
Paper
Notched-noise method—Patterson, 1976, cited for better estimates of frequency selectivity.