Ahroon W A, Hamernik R P
Auditory Research Laboratory, Plattsburgh State University of New York, 12901-2681, USA.
Hear Res. 1999 Mar;129(1-2):101-10. doi: 10.1016/s0378-5955(98)00227-5.
The auditory system, toughened by an interrupted noise exposure, has been shown in several reports to be less affected by (or protected from) a subsequent high-level noise exposure. Exposure to 115 dB peak SPL, 1 kHz narrow band (400 Hz) transients presented l/s, 6 h/day, to four groups of chinchillas produced a 10-28 dB toughening effect across the 0.5-8.0 kHz test frequency range. Following either a 30 day or an 18 h recovery period the animals were exposed to the same impulses but presented at 121 or 127 dB peak SPL for five uninterrupted days, thus producing an asymptotic threshold shift (ATS) condition. Comparisons between toughened and untoughened control subjects showed: (1) During the 121 dB exposure there was a statistically significant reduction of 10-25 dB in ATS across the entire test frequency range. Thirty days following the 121 dB exposure there were no significant differences in the postexposure permanent effects on thresholds and sensory cell loss. (2) During the 127 dB exposure only the group with the 30 day interval between the toughening and traumatic exposures showed a small (approximately 10 dB), statistically significant, frequency-specific (8 kHz), reduction in ATS. Thirty days following the 127 dB exposure a statistically significant protective effect on threshold was measured only at 16.0 kHz. However, both toughened groups showed less inner hair cell loss at and above 1.0 kHz, while only the group with the 18 h interval between the toughening and traumatic exposures showed less outer hair cell loss at and above 1.0 kHz. There were no systematic differences in the response of the toughened animals that could be attributed to the 30 day or 18 h post-toughening interval.
几份报告显示，经间歇性噪声暴露强化后的听觉系统，对随后的高强度噪声暴露影响较小（或受到保护）。对四组龙猫每天6小时、每秒呈现1次115 dB峰值声压级、1 kHz窄带（400 Hz）瞬态噪声，在0.5 - 8.0 kHz测试频率范围内产生了10 - 28 dB的强化效果。在30天或18小时的恢复期后，让这些动物暴露于相同的脉冲噪声，但峰值声压级为121或127 dB，连续暴露5天，从而产生渐近阈值偏移（ATS）状态。强化组与未强化对照组的比较结果表明：（1）在121 dB暴露期间，整个测试频率范围内的ATS在统计学上显著降低了10 - 25 dB。121 dB暴露30天后，暴露后对阈值和感觉细胞损失的永久性影响没有显著差异。（2）在127 dB暴露期间，只有在强化暴露和创伤性暴露之间间隔30天的组，显示出ATS有小幅（约10 dB）、统计学上显著的、频率特异性（8 kHz）降低。127 dB暴露30天后，仅在16.0 kHz处测量到对阈值有统计学上显著的保护作用。然而，两个强化组在1.0 kHz及以上频率处的内毛细胞损失均较少，而只有在强化暴露和创伤性暴露之间间隔18小时的组在1.0 kHz及以上频率处的外毛细胞损失较少。强化后间隔30天或18小时的强化动物的反应没有系统性差异。
