Subject: Re: ear defenders/sound attenuation From: "Meinke, Deanna" <Deanna.Meinke@xxxxxxxx> Date: Fri, 10 Feb 2006 15:50:41 -0700The 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 http://www.cdc.gov/niosh/topics/noise/hpcomp.html 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 Deanna.Meinke@xxxxxxxx ________________________________ From: AUDITORY Research in Auditory Perception on behalf of Mike Ravicz Sent: Fri 2/10/2006 3:02 PM To: AUDITORY@xxxxxxxx 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@xxxxxxxx "Are you going to come quietly, or do I have to use earplugs?" - Spike Mulligan