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Re: ear defenders/sound attenuation

Hello Gerry,

It's been a few years since I've looked at this, but... My recollection is that the performance among inexpensive commercial dielectric earmuffs/ear defenders with both large and small earcups is all pretty similar at moderate and high frequencies (above 500 Hz or so) but that earmuffs with smaller earcups were worse at low frequencies: 2-5 dB less attenuation at a few hundred Hz. By looking in a handful of industrial and laboratory supply catalogues we found a wide variety of choices - maybe 12-15 different models. Such catalogues usually give just a frequency-average NRR value, but a little poking around on the Web can usually provide attenuations at different frequencies.

Keep in mind that anything to disrupt the seal between the earmuff cushion and the subject's skin will degrade performance (e.g., hair, glasses, prominent jaw, etc.). Some people have looked at heavier gel cushions - I think they provide more attenuation (and perhaps a better seal) at low freqs.
- Mike Ravicz

Mike Ravicz, Eaton-Peabody Lab., Mass. Eye & Ear Inf., Boston MA 02114 USA
+1 (617) 573-5591; FAX +1 (617) 720-4408; mike_ravicz@xxxxxxxxxxxxxxxx
"Are you going to come quietly, or do I have to use earplugs?" - Spike Mulligan