Ahroon W A, Hamernik R P, Davis R I
Auditory Research Laboratory, State University of New York, Plattsburgh 12901.
J Acoust Soc Am. 1993 Feb;93(2):997-1006. doi: 10.1121/1.405406.
Industrial noise environments usually present a complex stimulus to the exposed individual. These environments often contain mixtures of multiply reflected impact noises and a relatively Gaussian broadband noise. Noise exposure standards do not consider the possibility of interactions between the two classes of noise that can exacerbate the amount of hearing trauma. This paper presents the results of a large series of experiments designed to document the hazard posed to hearing from complex noise exposures. Twenty-three groups of chinchillas with 5 to 11 animals per group (total N = 135) were exposed for 5 days to either octave bands of noise, impacts alone, or combinations of impact and octave bands of noise. Evoked potential measures of hearing thresholds and cochleograms were used to quantify the noise-induced trauma. The results show that, for sound exposure levels (SEL) which produce less than approximately 10 dB PTS (permanent threshold shift) or 5% total sensory cell loss, equal-energy exposures tend to produce equivalent effects on hearing. However, there is a range of at least 10 dB in the SEL parameter where hearing loss from equal-energy exposures at a particular SEL can be exacerbated by increasing the repetition rate of the impacts or by the addition of a Gaussian low-level noise. The exacerbation of trauma from the addition of a Gaussian continuous noise is dependent upon the spectrum of that noise.
工业噪声环境通常会给暴露其中的个体带来复杂的刺激。这些环境中常常包含多重反射撞击噪声和相对呈高斯分布的宽带噪声的混合。噪声暴露标准并未考虑这两类噪声之间相互作用从而加剧听力损伤程度的可能性。本文呈现了一系列大量实验的结果，这些实验旨在记录复杂噪声暴露对听力造成的危害。23组龙猫，每组有5至11只动物（总数N = 135），分别暴露于八度噪声频段、单独的撞击声或撞击声与八度噪声频段的组合环境中5天。使用听力阈值的诱发电位测量和耳蜗电图来量化噪声诱发的损伤。结果表明，对于产生小于约10 dB永久性阈值偏移（PTS）或5%总感觉细胞损失的声暴露水平（SEL），等能量暴露往往会对听力产生等效影响。然而，在SEL参数中至少存在10 dB的范围，在该范围内，特定SEL下的等能量暴露所导致的听力损失会因撞击重复率的增加或添加高斯低水平噪声而加剧。添加高斯连续噪声导致的损伤加剧取决于该噪声的频谱。
