Response to "Comment on 'ISO estimates of noise-induced hearing impairment' " [J. Acoust. Soc. Am. 157, 2404-2407 (2005)].

The main thesis of the Michel et al. Letter to the Editor is an assumption that the committee drafting ISO 1999 [ISO (1990). (International Organization for Standardization, Geneva, Switzerland)] used hearing threshold levels (HTLs) in Annex A, taken from ISO 7029 [ISO (1984). International Organization for Standardization, Geneva, Switzerland)], to represent the non-noise exposed population HTLs, H, in its formula for predicting the effect of noise, N. This assumption is novel and undocumented. There is no reason to assume that the developers of ISO 1999 [ISO (1990). (International Organization for Standardization, Geneva, Switzerland)] used anything but what the authors of the [Burns and Robinson (1970). Hearing and Noise in Industry (Her Majesty's Stationery Office, London, UK)] and [Passchier-Vermeer (1977). (Research Institute for Environmental Hygiene, Bilthoven, the Netherlands)] models reported for their non-noise comparison populations.