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Activities: NIOSH Funded Research Grants

Hearing Hazard Associated with Industrial Noise Exposure

This project is relevant to the mission of the NIOSH Hearing Loss Cross-Sector Program. This program seeks to reduce the prevalence of occupational hearing loss (OHL) through research, prevention, engineering controls, personal protective equipment, and improved understanding of OHL through surveillance and investigation of risk factors.

The equal energy hypothesis (EEH) is the basis of current noise exposure criteria. However, the application of the EEH in many industrial environments severely underestimates hearing loss. Project researchers have been studying in an animal model the effects that the statistical properties of a complex noise exposure, as embodied in a single number metric, the kurtosis [(ßt)], have on hearing. The kurtosis has been shown to be important in identifying and quantifying the hazard to hearing from complex industrial noise environments. This project has a single specific aim: to develop an understanding of how the variables that define a complex noise affect hearing loss for a fixed value of the kurtosis. One issue that must be addressed to establish guidelines for using [(ßt)] in noise assessment and measurement practice is to understand how peak, interval, and impact duration levels affect hearing trauma at a constant ß(t). Such data is a necessary prerequisite to the application of ß(t) to industrial hearing conservation/noise measurement protocols. This data will also contribute to our continuing evaluation, application, and understanding of the EEH.

The proposed research is aimed at developing a new noise measurement and evaluation strategy that will predict the potential of an industrial noise to produce hearing loss. For a given sound pressure level and spectrum of a noise, any realistic combination of the three 'primary variables' that yield the same value of ß(t) will produce the same hearing loss. If this hypothesis can be shown to be true, then the evaluation of industrial noises for hearing conservation purposes will be greatly simplified by using an energy metric and an appropriate ß(t) value.