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Re: ear defenders/sound attenuation

The National Institutes for Occupational Safety & Health (NIOSH) has a Hearing Protector Compendium online. 
You can search over 250 types of hearing protectors via a variety of methods, many of the passive devices have become more sophisticated in terms of flatter attenuation responses or varying degrees of attenuation dependent upon the need for protection and communication demands.
Perhaps the compendium would be helpful to others; it can be found at 
Deanna Meinke Ph.D.
Assistant Professor of Audiology
University of Northern Colorado
College of Natural and Health Sciences
Audiology and Speech-Language Sciences
Campus Box 140
Greeley, CO  80639
Voice:  970-351-1600
Fax:    970-351-2974


From: AUDITORY Research in Auditory Perception on behalf of Mike Ravicz
Sent: Fri 2/10/2006 3:02 PM
To: AUDITORY@xxxxxxxxxxxxxxx
Subject: Re: [AUDITORY] 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