Simple rating of hearing-protector effectiveness

Abstract

Although hearing protectors should ideally be rated according to how much attenuation they provide in the actual noise in which they are worn, testing them that way is impractical. Compromises have been suggested; all are based on the ANSI “Measurement of the Real-Ear Attenuation of Ear Protectors at Threshold” (Z24.22-1957, R1971). In general, the effectiveness in noise of an ear protector is calculated from the Standard measurement of attenuation and from the spectrum of the noise. If the noise spectrum is unknown, the protector's average response in a number of typical noises is used. Such estimated attenuation values may be calculated to show the likely effectiveness for the worst case in any proportion of the population of users. Thus, a rating number might refer to the ear protector's performance with 50% of the population or any other preselected percentage. This paper describes two- and three-digit figures-of-merit for rating the effectiveness of ear protectors in most noise environments and for a range of percentages of users. Each digit is selected to represent the performance of the device-under-test relative to the performance of a large number of similar devices. Although the procedure for computing the number is complex, its meaning is simple and should be easy for most prospective users to understand.