Cochlear toughening, protection, and potentiation of noise-induced XXXX by non-Gaussian noise.

@entity1442 @entity16811 @entity130 @entity393
An interrupted noise exposure of sufficient intensity, presented on a daily repeating cycle, produces a @entity1442 ( @entity1442 ) following the first day of exposure. TSs measured on subsequent days of the exposure sequence have been shown to decrease relative to the initial @entity1442 . This reduction of @entity1442 , despite the continuing daily exposure regime, has been called a cochlear toughening effect and the exposures referred to as toughening exposures. Four groups of chinchillas were exposed to one of four different noises presented on an interrupted (6 h/day for 20 days) or noninterrupted (24 h/day for 5 days) schedule. The exposures had equivalent total energy, an overall level of 100 dB(A) @entity16811 , and approximately the same flat, broadband long-term spectrum. The noises differed primarily in their temporal structures; two were Gaussian and two were non-Gausssian, nonstationary. Brainstem auditory evoked potentials were used to estimate hearing thresholds and surface preparation histology was used to determine sensory cell loss. The experimental results presented here show that: (1) Exposures to interrupted high-level, non-Gaussian signals produce a toughening effect comparable to that produced by an equivalent interrupted Gaussian noise. (2) Toughening, whether produced by Gaussian or non-Gaussian noise, results in reduced @entity130 compared to the equivalent uninterrupted noise, and (3) that both continuous and interrupted non-Gaussian exposures produce more @entity130 than do energy and spectrally equivalent Gaussian noises. Over the course of the 20-day exposure, the pattern of @entity1442 following each day's exposure could exhibit a variety of configurations. These results do not support the equal energy hypothesis as a unifying principal for estimating the potential of a noise exposure to produce @entity393 .
