A PROTOTYPE ACTIVE NOISE-REDUCTION IN-EAR HEARING PROTECTOR

The acoustic performance of five prototype in-ear hearing protectors was measured in the laboratory and in a military vehicle. Where a conventional or Active Noise Reduction (ANR) circum-aural headset is worn over a protective hood and/or respirator an acoustic leak occurs, degrading the hearing protection. In a noisy environment which contains a predominance of frequencies below 1 kHz and where it is essential to wear other headgear, a possible solution is offered by ANR in-ear hearing protection. The acoustic performance was measured using the in-built sense microphone. Noise at the ear was reduced from a sound pressure level of 112 dB(A) to below 90 dB(A) with the ANR 'on'. The combined passive and active attenuation provided better protection than passive attenuation only. The acoustic performance of these prototypes was satisfactory, but the prototypes need to be easier to fit and more robust for military applications.