Hearing Hazard Associated with Industrial Noise Exposure

描述：工业噪声环境通常由非高斯、非平稳、时变噪声组成。评估听力危害的另一个复杂因素是工人每天接触的间歇性。文献中几乎没有关于这种最普遍和最现实的工业噪声暴露类型的数据。我们建议建立这种暴露条件的基本特征模型，并确定暴露的听力学和组织学后果。所提出的实验数据将解决与我们对噪声效应研究中以下问题领域的理解相关的问题。这些都是当代的问题，对制定一个全面的损害风险标准至关重要。(1)等能量假设（EEH）构成了当前噪声暴露的损害风险标准的基础，对暴露的时间特征不敏感。EEH在什么曝光条件下适用？它的局限性是什么？峰度度量是Leq的必要附属物吗？(2)时变和间断的非高斯暴露条件对噪声性听力损失的影响程度有多大？(3)中断曝光所产生的“增韧”现象的影响（如果有的话）是什么？干扰能减少噪音引起的听力损失吗？以栗鼠（n-150）为动物模型，诱发反应听力学用于估计纯音阈值（听力图），表面制备组织学用于量化耳蜗感觉细胞的损失。提出的实验是我们目前工作的延伸，以更广义和现实的暴露条件。预计将获得的数据将有助于峰度度量的发展及其在风险评估中的应用。所有的暴露都将模拟一个理想的工作日/周（每天8小时，不间断，每周5天），持续三周。每次曝光（高斯或非高斯）将与具有等效能量和光谱的不变的、不间断的对照曝光（24小时/天，5d）配对。重要的是要了解现实工业噪声环境的哪些特征对听力构成最大的危害，并制定可靠的风险评估指标。将建立一个由大约150名受试者在18种不同的复杂噪声暴露条件下运行的结果组成的数据库。统计度量、峰度、峰值声压级和峰值/间隔直方图、波峰因子以及复杂噪声暴露的时间变化/中断模式将发生变化。为了确保在独立变量（噪声参数）和依赖变量（创伤测量）之间建立的相关性的统计能力，大样本量和广泛的暴露参数变化是必要的。

DESCRIPTION: Industrial noise environments typically consist of non-Gaussian, non-stationary, time varying noise. An additional complication for the assessment of hearing hazard is posed by the intermittent nature of the worker's daily exposure. There is virtually no data available in the literature on this most general and realistic type of industrial noise exposure. We propose to model the essential features of such exposure conditions and determine the audiometric and histological consequences of exposure. Data from the proposed experiments will address issues germane to our understanding of the following problematic areas in noise effects research. These are contemporary issues that are critical to the development of a comprehensive damage-risk criterion. (1) The equal energy hypothesis (EEH) which forms the basis of current damage-risk criteria for noise exposure is insensitive to the temporal features of an exposure. Under what exposure conditions is the EEH applicable? What are its limitations? Is the kurtosis metric a necessary adjunct to the Leq? (2) To what extent is noise-induced hearing loss affected by time varying and interrupted non-Gaussian exposure conditions? (3) What is the influence, if any, of the 'toughening' phenomenon, produced by interrupted exposures? Does interruption reduce noise-induced hearing loss? The chinchilla (n-150) will be used as the animal model, evoked response audiometry will be used to estimate pure tone thresholds (audiograms) and surface preparation histology will quantify cochlear sensory cell loss. The proposed experiments are an extension of our current work to more generalized and realistic exposure conditions. The data that will be acquired are expected to contribute to the development of the kurtosis metric and its application to risk assessment. All exposures will model an ideal work-day/week (8h/day with interruption, 5day/week) and last for a period of three weeks. Each exposure (either Gaussian or non-Gaussian) will be paired with an unvarying, uninterrupted control exposure (24h/day, 5d) having equivalent energy and spectrum. It is important to understand what features of realistic industrial noise environments pose the greatest hazard to hearing and to develop a reliable metric for risk assessment. A database consisting of results from approximately 150 subjects run through 18 different complex noise exposure conditions will be constructed. The statistical metric, kurtosis, the peak SPL and peak/interval histograms, the crest factor, and the pattern of temporal variation/interruption of the complex noise exposure will be varied. A large sample size and a wide variation of exposure parameters are necessary to insure statistical power for the correlations that will be made among the independent (noise parameters) and dependent (measures of trauma) variables.