The chinchilla animal model for noise-induced hearing loss has an extensive history spanning more than 50 years. Many behavioral, anatomical, and physiological characteristics of the chinchilla make it a valuable animal model for hearing science. These include similarities with human hearing frequency and intensity sensitivity, the ability to be trained behaviorally with acoustic stimuli relevant to human hearing, a docile nature that allows many physiological measures to be made in an awake state, physiological robustness that allows for data to be collected from all levels of the auditory system, and the ability to model various types of conductive and sensorineural hearing losses that mimic pathologies observed in humans. Given these attributes, chinchillas have been used repeatedly to study anatomical, physiological, and behavioral effects of continuous and impulse noise exposures that produce either temporary or permanent threshold shifts. Based on the mechanistic insights from noise-exposure studies, chinchillas have also been used in pre-clinical drug studies for the prevention and rescue of noise-induced hearing loss. This review paper highlights the role of the chinchilla model in hearing science, its important contributions, and its advantages and limitations.

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Recent findings from animal studies suggest that moderate-level acoustic overexposure can produce permanent cochlear synaptopathy while not significantly affecting hearing thresholds in quiet. It has been hypothesized that this hidden hearing loss may underlie difficulties some listeners have in noisy situations even with normal audiograms. However, this hypothesis has not been tested directly due to difficulties measuring behavior in animal models for which cochlear synaptopathy has been demonstrated, and the inability to measure cochlear synaptopathy directly in humans. We recently established a mammalian model (chinchilla) that has corresponding neural and behavioral amplitude-modulation (AM) detection thresholds in line with human behavioral thresholds, and which shows cochlear synaptopathy following moderate noise exposure. Here, behavioral AM-detection thresholds were measured in six chinchillas, before and after noise exposure, using the method of constant stimuli. Animals were trained to discriminate a sinusoidal AM (SAM) tone (4-kHz carrier) from a pure tone, in the presence of a notched-noise masker. Behavioral thresholds before noise exposure were consistent across individual animals and were in the range from -25 to -15 dB. Preliminary data collected following noise exposure do not show a substantial effect on AM-detection thresholds in this simple task. [Work supported by NIH grant R01-DC009838.]