ABSTRACT
Hearing protectors, unless specifically designed, attenuate the higher frequency sound energy more than lower frequency energy. Because such a nonuniform attenuation characteristic can be less than optimal for certain high-fidelity requirements, acoustically tuned hearing protectors were developed. These include the ER-15 and the ER-25 earplugs that-as the name suggests-provide a uniform attenuation of 15 dB and 25 dB, respectively. To obtain different attenuation characteristics, modifications of these earplugs are clinically possible, but they will lose their uniform attenuation property. Such earplugs can be used in the performing arts and in industrial settings with noise levels below 100 dBA. The ER-20 (or HI-FI earplug) noncustom earplug also is available. Objective techniques, such as microphone-in-real-ear (MIRE) and the use of acoustical test fixtures (ATF), and subjective techniques, such as real ear attenuation thresholds (REAT), are two valid methods for assessing the effects of hearing protection. Regardless of the technique, the resulting data can be expressed in a single number rating scheme such as the Noise Reduction Rating (NRR).
KEYWORDS
Attenuation - hearing protector - ER-15 - NRR - noise
