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Early indicators of noise-induced hearing loss: issues for consideration.

Murphy WJ; Stephenson MR; Franks JR
Spectrum 2005 Feb; 22(Suppl 1):24
The precursor of noise-induced hearing loss (NIHL) often is manifested by a marked shift in the hearing at audiometric frequencies 2 to 6 kHz with a recovery at frequencies above the shift. The noise-induced notch index has been proposed as the difference between the pure-tone averages of 2, 3 and 4 kHz and the pure tone average at 1 and 8 kHz [Rabinowitz and Dobie, Spectrum, 20:8-11, 2003]. The notch index and two variants of the calculation were tested against a set of 3320 audiograms collected from subjects that participated in the National Health and Nutrition Examination Survey (NHANES IV) during the years 1999 and 2000. A strict notch definition yielded 397 audiograms that contained a notch. Three variations of the notch index were tested using the subset of audiograms. The average difference in pure-tone averages using 2, 3 and 4 kHz had a mean notch index of 0.5 + 6.1 dB. The average difference in pure-tone averages using 2, 3. 4 and 6 kHz had a mean notch index of 4.1 + 2.9 dB. The average area difference using 2, 3, 4 and 6 kHz had a mean notch index of 7.4 + 6.3 dB. The results of the analysis demonstrate that the notch index is more effective when 6 kHz is included in determining whether a subject has a noise-induced notch.
Noise-induced-hearing-loss; Audiometry; Hearing-loss; Noise-exposure; Noise-frequencies; Audiofrequency; Noise-levels
Publication Date
Document Type
Abstract; Conference/Symposia Proceedings
Fiscal Year
NIOSH Division
Priority Area
Disease and Injury: Hearing Loss; Construction
Source Name
Spectrum: the National Hearing Conservation Association newsletter
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division