| 1. |
- Grenner, Jan, et al.
(författare)
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Action potential threshold elevation in the guinea-pig as a function of impact noise exposure energy
- 1988
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Ingår i: Audiology. - : Informa UK Limited. - 0020-6091. ; 27:6, s. 356-366
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Tidskriftsartikel (refereegranskat)abstract
- Eighteen groups of guinea pigs were exposed to a simulated impact noise for periods of 1.5-24 h. The peak level was kept constant at 131.5 dB and the repetition rate was varied to give seven different equivalent levels (Leq) between 96 and 117 dB. The auditory thresholds were assessed by electrocochleography after 1 month and compared with those of a control group. Significant damage occurred even at the lowest exposure energy used. When the total exposure energy was expressed on a decibel scale, the threshold elevation (1-10 kHz) increased 1.07 dB for each decibel increase in the exposure energy, regardless of the combination of Leq and exposure time. The results of the study thus support the equal-energy hypothesis under these conditions.
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| 2. |
- Grenner, Jan, et al.
(författare)
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AP threshold elevation in the guinea pig following exposure to a broadband noise
- 1989
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 86:6, s. 2223-2228
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Tidskriftsartikel (refereegranskat)abstract
- Sixty guinea pigs were exposed to a steady-state broadband noise with a falling frequency spectrum. The sound-pressure level was varied between 96 and 117 dB SPL, and the duration of the exposure was varied from 3 to 12 h. After 4-5 weeks, the auditory thresholds were determined by electrocochleography at 14 frequencies, and the results were compared with a control group. With increasing sound-pressure level, the thresholds became elevated at all frequencies. The maximum threshold elevation also exhibited a slight shift toward higher frequencies. With increasing exposure time, the threshold elevations increased and shifted into the high-frequency region, whereas the low-frequency region was less affected. Linear regression analysis showed that the average threshold elevation between 1 and 20 kHz did not deviate from that predicted by the equal-energy hypothesis. However, the high-frequency loss at 5-20 kHz was very dependent on the exposure time, whereas the 1- to 4-kHz loss was not. There was no sign of any critical intensity with sudden increments in threshold elevation.
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| 3. |
- Nilsson, P, et al.
(författare)
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Impulse noise and continuous noise of equivalent frequency spectrum and total sound energy
- 1987
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Ingår i: Acta Oto-Laryngologica. Supplement. - : Informa UK Limited. - 0365-5237 .- 0001-6489 .- 1651-2251. ; 104:S 441, s. 45-58
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Tidskriftsartikel (refereegranskat)abstract
- It has been proposed that impulse noise and continuous noise affect the inner ear differently and investigations have found impulse noise to be harmful to both the inner hair cells and the outer hair cells. Scanning electron microscopy and non-standard methods for statistical analysis have facilitated the evaluation of different types of morphological changes after exposure to various kinds of noise. Morphological differences were compared in groups of guinea pigs exposed to either impulse noise or continuous noise of equivalent duration, spectral content and energy. Functionally, the groups also showed similar threshold elevations. In order to separate the two groups, subtle hair cell changes were recorded and evaluated either alone, in combination with each other or with hair cell loss. It was found that both the inner hair cells and the outer hair cells were affected differently by impulse noise than by continuous noise even though the auditory thresholds were similar.
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| 4. |
- Rydmarker, S, et al.
(författare)
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Impulse noise of different durations
- 1987
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Ingår i: Acta Oto-Laryngologica. Supplement. - : Informa UK Limited. - 0365-5237 .- 0001-6489 .- 1651-2251. ; 104:S 441, s. 3-23
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a comparison between auditory threshold elevations and morphological cochlear changes evaluated with scanning electron microscopy in order to identify cochlear defects in guinea pigs exposed to impulse noise of varying durations. There was a significant difference in the auditory threshold shifts between animals exposed for 3 and 12 hours. Hair cell loss is generally used as a morphological correlate to noise-induced hearing loss. Minor stereocilia changes, quantified with non-standard statistical methods have been used as a complement. Morphologically, it was not possible to separate cochleas exposed to impulse noise for 3 and 12 hours when only lost hair cells were evaluated. Quantitative evaluation of subtle morphological changes are valuable in the correlation of noise-induced hearing loss with morphologic changes.
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