Roberto M, Zito F, Hamernik R, Ahroon B, Case C
Cattedra di Bioacustica, Università di Bari.
Acta Otorhinolaryngol Ital. 1995 Apr;15(2):61-4.
The EEH (Equal Energy Hypothesis) postulates that permanent hearing loss (PTS) produced by exposure to noise is a function of sound energy of the exposure. The validity of EEH for continuous noise exposure was confirmed by large scale demographic studies and experiments in controlled laboratory setting. However, for impulse noise, EEH may not be as valid. This study was designed to test the applicability of EEH in impulse noise exposure in chinchillas. 9 groups of chinchillas were exposed to impulse noise. The intensity of the impulses (113, 125 and 137 dB SPL) and the rate (900, 3,600 and 14,400 impulses/hour) of the 9 exposure conditions were counterbalanced so that the 9 groups received the same total energy. PTS was obtained at 0.5, 2. and 8.0 kHz, by recording the evoked potentials from a chronic electrode implanted in the inferior colliculus. The cochleas were dissected and evaluated using conventional histological surface preparations and examined through scanning electron microscopy (SEM) employing a JEOL 35 microscopy. In our experimental conditions only the 113 dB SPL exposures were consistent with EEH (PTS less than 20 dB). The 125 dB SPL peak level is a critical value in that the validity of EEH also depends on exposure duration. As duration increases, so does PTS. At a 137 dB SPL peak level, EEH is not applicable. The amount of PTS is higher than 50 dB. It slightly increases when the impulse rate per hour becomes higher. In all cases examined PTS is less at 0.5 kHz than at 2.0 or 8 kHz. In these animals excellent informations concerning the sensory cell losses and cells damage was obtained with SEM.
等能量假说（EEH）假定，暴露于噪声导致的永久性听力损失（PTS）是暴露声能的函数。大规模人口统计学研究以及在受控实验室环境下进行的实验证实了EEH对于连续噪声暴露的有效性。然而，对于脉冲噪声，EEH可能不太适用。本研究旨在测试EEH在栗鼠脉冲噪声暴露中的适用性。9组栗鼠暴露于脉冲噪声。对9种暴露条件下的脉冲强度（113、125和137 dB SPL）和速率（900、3600和14400次脉冲/小时）进行了平衡处理，以便9组接受相同的总能量。通过记录植入下丘的慢性电极诱发的电位，在0.5、2和8.0 kHz处获得PTS。解剖耳蜗并使用传统组织学表面制剂进行评估，并通过使用JEOL 35显微镜的扫描电子显微镜（SEM）进行检查。在我们的实验条件下，只有113 dB SPL的暴露符合EEH（PTS小于20 dB）。125 dB SPL的峰值水平是一个临界值，因为EEH的有效性还取决于暴露持续时间。随着持续时间增加，PTS也增加。在137 dB SPL的峰值水平下，EEH不适用。PTS量高于50 dB。当每小时的脉冲率变得更高时，它会略有增加。在所有检查的情况下，0.5 kHz处的PTS低于2.0 kHz或8 kHz处的PTS。在这些动物中，通过SEM获得了有关感觉细胞损失和细胞损伤的出色信息。
