AN ALTERNATIVE MODEL FOR COMBINING NOISE AND AGE-INDUCED HEARING-LOSS

Bies and Hansen [J. Acoust. Soc. Am. 88, 2743-2754 (1990)] have proposed an alternative formulation of the relationship between noise exposure and noise-induced hearing impairment to that presented in International Standard ISO 1999 to demonstrate that the interpretation of the standard is not unique. J. H. Macrae [J. Acoust. Soc. Am. 90, 2513-2516 (1991)] has shown that neither the Bies and Hansen formulation nor the International Standard accounts for observed deterioration in hearing threshold levels at 4000 Hz associated with aging in war veterans with noise-induced permanent threshold shift (NIPTS). Thus Macrae has shown that at present there is no formulation which accounts for all epidemiological data. It is shown that Macrae's data provides an opportunity to extend the formulation of Bies and Hansen without altering in any way their representation of the International Standard database to represent the new epidemiological data for post exposure provided by Macrae as well. A similar extension of the formulation of Kraak and co-investigators may be shown. If the International Standard is corrected, as suggested by Macrae, and the extensions of the formulations of Bies and Hansen and of Kraak and co-investigators are accepted, then there will be three formulations which account for all of the epidemiological data.