of engineering and administrative noise controls remained; in addition to other facets of a hearing conservation program (including noise monitoring, employee notification, audiometric testing, worker training, access to information and training materials, and exposure and audiometric recordkeeping), the amendment specified the use of HPDs in more detail.
Perhaps the most significant addition, at 29 CFR 1910.95(i), was (1) that “employers shall make hearing protectors available to all employees exposed to an 8-hour time-weighted average of 85 decibels or greater at no cost to the employees. Hearing protectors shall be replaced as necessary” and (2) that “employers shall ensure that hearing protectors are worn: (i) by an employee who is required by paragraph 1910.95(b)(1) of this section to wear personal protective equipment [i.e., mandatory HPD use at exposures equal to or greater than 90 dB(A) TWA] and (ii) by any employee who is exposed to an 8-hour TWA of 85 decibels or greater, and who” has not had a baseline audiogram, or who has experienced a standard threshold shift (as defined by OSHA). In addition, employers were required, under paragraph 3, to provide “a variety of suitable hearing protectors” for the employee to select from; under paragraph 4 to provide training in the use and care of all hearing protectors; and under paragraph 5 to ensure proper initial fitting and supervision in the correct use of all hearing protectors. Finally, in part (j) the amendment specified computational procedures for evaluating HPDs for adequacy of protection in specific noise exposures, with the requirement that the protected exposure levels be brought to less than or equal to 90-dB(A) TWA, or to less than or equal to 85-dB(A) TWA if the worker has experienced a standard threshold shift.1
The OSHA Hearing Conservation Amendment greatly impacted the requirements for hearing protection, and the numbers of HPDs supplied in occupational settings dramatically increased as a result. Although engineering or administrative controls were still required for TWA exposures above 90 dB(A), the amendment provided, at no cost to workers, a selection of HPDs to everyone exposed to 85-dB(A) TWA or above. The 5-dB(A) difference between the 90-dB(A) OSHA “criterion” level imposed as a result of OSHA (1971) and the 85-dB(A) OSHA “action” level imposed as a result of the 1983 OSHA Hearing Conservation Amendment defined an exposure window wherein thousands of workers who had not been protected by law were now to be supplied with a selection of suitable HPDs.
In this sense the new 85-dB(A) TWA action level was a major step forward in protecting workers against the hazards of noise exposures; however, the OSHA Hearing Conservation Amendment should not be understood as an indication that HPDs are preferable to engineering noise controls, which do not require human intervention to protect workers’ hearing and prevent noise-induced hearing loss.
The labeling of HPDs has been the subject of debate for more than two decades, much of it about the differences between on-package EPA-required attenuation data and the actual protection provided for users in the field (Berger and Casali, 1997; Casali and Robinson, 2003). To comply with OSHA (1983) and other applications, the adequacy of an HPD for a given noise exposure is determined by subtracting, in a prescribed way, the attenuation data required by the U.S. Environmental Protection Agency (EPA) from the TWA noise exposure for the affected worker (see OSHA, 1983, Appendix B: Methods for Estimating the Adequacy of Hearing Protector Attenuation).
Attenuation data are obtained from psychophysical real-ear-attenuation-at-threshold tests at nine 1/3-octave bands with centers of 125 to 8,000 Hz performed on human listeners; the signed, arithmetic difference between thresholds with the HPD and without it constitutes the attenuation at a given frequency. Both the spectral attenuation statistics (means and standard deviations) and the broadband single-number noise reduction rating (NRR), which is computed there from, are provided, and either of them can be used to estimate HPD adequacy for a given exposure, per OSHA (1983) Appendix B.
Labeled ratings are the primary means by which end users compare different HPDs and determine if they will provide adequate protection and OSHA compliance in a given noise environment. Therefore, the accuracy and validity of label ratings are very important.
The labeling of hearing protectors is controlled by EPA via federal law per 40 CFR Part 211, Subpart B, which was promulgated in September 1979 and remains in effect as of this writing. This section of the law applies to “any device or material, capable of being worn on the head or in the ear canal, that is sold wholly or in part on the basis of its ability to reduce unwanted sound that enters the user’s ears” (40 CFR Part 211, Subpart B). Unfortunately, the law references an outdated, superseded ANSI standard (1974) for obtaining the real-ear attenuation of threshold data on which the EPA label, which includes an NRR, is based.
The data on HPD packaging are obtained under optimal laboratory conditions with properly fitted protectors worn by trained, well-practiced human subjects. However, numerous research studies (e.g., Berger et al., 1998; Berger and Casali, 1997; Park and Casali, 1991) have shown that the “experimenter-fit” protocol and other aspects of the EPA-