An acoustic head simulator for hearing protector evaluation. II: Measurements in steady-state and impulse noise environments.

The attenuation characteristics of hearing protection devices (HPDs) were measured using a modular acoustic head simulator. The effect in changes in the head configuration was assessed in a steady-state diffuse sound field. The use of artificial circumaural skin had a relatively small influence on the insertion loss of earmuffs (max. 6-7 dB at low frequencies). This contrasts to the very large effects found for the artificial intraaural skin on the insertion loss of earplugs (in excess of 40 dB at low frequencies for some devices). Results were also compared with real-ear attenuation at threshold (REAT) data (ANSI S3.19-1974). In general, there is good agreement between the two methods, especially for earmuffs. Design improvements are proposed for earplugs. The result of an exploratory study aimed at measuring the complex (amplitude and phase) insertion loss of HPDs using an impulse noise source are also reported.