Abstract
Several real-ear attenuation at threshold (REAT) standards govern the attenuation testing of hearing protectors internationally. A characteristic common to many is the requirement of a diffuse sound field and the toleration of a wide range of reverberation times, allowing testing in an anechoic or a reverberant test room. This study explored the degree to which the diffuse environment can be degraded without significantly affecting the attenuation tested under ANSI S3.19-1974. In addition, the study compared a diffuse sound field generated in a reverberant room (as required by ANSI S3.19-1974 and CSA Z94.2-M1984) with a diffuse sound field generated in an anechoic room (as allowed by ANSI S12.6-1984, BSI 5108:1983, ISO 4869-1(E):1990, and SS 882151). Results indicate that degrading the diffusivity will result in statistically significant changes in attenuation, but the magnitude of change is small. In addition, small but significant differences exist between the two test chambers. Interpretation of these results depends upon the purpose of the testing. For applications where accuracy is critical, the statistically significant differences should not be ignored. However, for noncritical applications, such as simply predicting the amount of attenuation a particular worker is receiving with a specific hearing protector, the small magnitude of these differences do not preclude the use of these alternative environments. Therefore, actual protection levels achieved in the field can be empirically verified in either sound field.
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