Groups of chinchillas were given a series of noise exposures of approximately equal energy ranging from 22 minutes at 120 dB SPL to 150 days at 82 dB. For all exposures involving levels of 112 dB or less, the same average permanent hearing losses (15-20 dB) and degree of outer hair cell destruction (8-10%) resulted, thus confirming the validity of the total energy principle for assessing the hazard associated with single continuous exposures at moderate levels. The 22-minute, 120-dB exposure, however, produced a 60-dB hearing loss and massive hair cell destruction (70-80%), indicating that some critical level had been exceeded, thus producing acoustic trauma. Further histological study suggests that the massive destruction is a result of breaks in the organ of Corti, produced by severe mechanical stress, that permit the mixture of endolymph with perilymph, thus creating a hostile environment for the hair cells.

Animals↗

PubMedDate not supplied

Hyperlipidemia and noise in the chinchilla.

Chinchillas were maintained on a 1% cholesterol diet for 6 months. Auditory Brainstem Response (ABR) measurements were obtained before and at 1, 3, 5, and 6 months after initiation of diet. Compound Action Potential (AP) measurements were obtained at sacrifice at 6 months. A significant reduction in ABR was seen at 5 months-on-diet. At 5 months, the animals were exposed to a 2 octave bandpass noise centered at 1 kHz at 105 dB for 220 min. One month following noise exposure, the cholesterol-fed animals exhibited a greater ABR latency shift at low intensities, and an elevated AP threshold at higher frequencies, vis-à-vis a control group.

Animals↗

PubMedDate not supplied

Diet-induced hyperlipidemia and auditory dysfunction.

Chinchillas rendered hyperlipidemic by a 1% cholesterol diet or maintained on a normal diet were either exposed to a 2-octave bandpass noise (700-2,800 Hz for 220 min at 105 or 114 dB) or else not exposed to noise. The animals were assessed with tone-burst (2-16 kHz) elicited compound action potentials (CAP). Compared with normal diet animals, the hyperlipidemic animals: not exposed to noise exhibited elevated thresholds at 8 kHz and higher frequencies; exposed to 105-dB noise exhibited elevated thresholds at 16 kHz; and exposed to 114-dB noise exhibited elevated thresholds at 2-16 kH. Surface preparations were made of the left cochleae of all noise-exposed animals. There was essentially no difference in hair cell counts between hyperlipidemic animals exposed to the 105-dB noise and normal animals similarly exposed. The hyperlipidemic animals exposed to the 114-dB noise exhibited a greater hair cell loss in the first turn of the cochlea than did similarly exposed normal animals. We conclude that maintenance on a high-cholesterol diet can cause a high-frequency hearing loss, probably due to vascular pathology resulting from a hyperlipidemic state. Furthermore, maintenance on a high-cholesterol diet can increase susceptibility to noise-induced hearing losses.

Animals↗

PubMedDate not supplied

Take a scientific look at the noise hazard.

Explore the source record for details and available documents.

Audiometry↗