ON SPATIAL VARIABILITY IN THE ATTENUATION PERFORMANCE OF ACTIVE HEARING PROTECTORS

As noise cancellation (ANR) hearing protectors enter the market-place, the question is being asked, `How should we assess their attenuation performance?'. With the introduction of new European and international standards for hearing protectors, there is a need to evolve appropriate attenuation test methods. One particular issue which relates to this type of device is the variability in cancellation achieved throughout the ear-muff cavity, and consequently the level of attenuation perceived by the user. Experimental data are presented to illustrate the effects of alternative design approaches to the problem.