Analysis of industrial noise for hearing conservation.
NIOSH 2001 May; :1-24
Noise measurements made for the purpose of hearing conservation practice has as their objective the extraction of some physical metric from the noise that can be used to estimate the hazards to hearing from prolonged exposure to noise. Current practice continues to rely primarily upon a time averaged, integrated approach to quantifying a noise exposure. Temporal variables are completely neglected. A variety of recent experiments have shown that an understanding of the temporal structure of a noise is critical to predicting the hazard to hearing. The objectives of this grant were to explore new and more generalized ways of quantifying industrial noise environments, especially those approaches that would result in metrics which incorporate the temporal and statistical properties of a nonGaussian noise. The metrics [frequency and time domain kurtosis and the joint peak-interval histogram] and the methods by which they can be obtained were developed as a result of this grant. These metrics can differentiate among noises that have the same energy and spectra but very different temporal patterns which have a profound effect on hearing hazard. Frequency domain kurtosis was obtained from an application of wavelet analysis to the noise waveform. Higher-order cumulant based inverse filtering was used to extract timing and peak amplitude information from a noise waveform having randomly occurring transient components. From this analytical process, the joint peak-interval histogram was obtained from which the cumulative distribution of both the timing and peak amplitudes of the repetitive components in a time-varying and highly nonGaussian waveform were also obtained; i.e., a timing interval histogram for a given amplitude or a peak-amplitude histogram for a given interval was derived from the joint peak-interval histogram. The temporal/statistically based metrics produced as a result of this grant (FDK and joint peak-interval histogram metrics), in conjunction with the energy metrics can provide a more complete set of measurement tools for evaluating noise environments in the assessment of the hazards to hearing. What remains to be done is to exhaustively test these metrics in an animal model of NIHL in order to evaluate their predictive value. If substantially improved correlations among cochlear pathology, measures of hearing and the new noise metrics are found, these new metrics can be incorporated into computer-based instrumentation for evaluating industrial noise environments. These metrics may also have engineering applications for identifying features of the noise that can be reduced at their source or for incorporation into the design of hearing protective devices.
Noise-measurement; Hearing-conservation; Hearing-disorders; Noise-exposure; Hearing-loss; Noise-waves; Analytical-processes; Noise-induced-hearing-loss; Animal-studies; Animals; Hearing-protection
Final Grant Report
NTIS Accession No.
Research Tools and Approaches: Exposure Assessment Methods
National Institute for Occupational Safety and Health
State University of New York, Plattsburgh, NY