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Re: acoustic shielding

a couple of points:
* the difficulty with sound insulation is blocking low frequencies -
high frequencies are generally solved if you meet your low frequency
* you might be able to estimate the characteristics of the desired
material using the simplistic assumptions of the 'mass law' for sound
the mass per square metre of material = 10^((attenuation+42)/20) / frequency.
That equation assumes normal sound incidence (not random incidence,
for which you probably need a bit more mass per square metre).  It
also has many other assumptions which may not apply, but it might be
a good start for a flexible material.
* one more hint - it is important to seal all air paths - the
material must be airtight.

Hi Satra,

you could try with small pieces of thick foam should do the
trick. this foam which is used for acoustic treatment: pads,
bass-traps and so one. not sure what it would give in only 8mm


On Fri, Jul 02, 2004 at 01:01:55AM -0400, Satrajit Ghosh wrote:
 Dear List members,

 We are trying to increase the external attenuation of a set of headphones.
 Do you know of any non-metallic, non-magnetic, thin [less than 8mm],
 pliable material that can provide noise suppression upwards of 10dB upto

 > Satra
 > --
 > Satrajit Ghosh
 > Department of Cognitive and Neural Systems, Boston University


Dr Densil Cabrera, Lecturer in Audio and Acoustics
School of Architecture, Design Science and Planning
Wilkinson Building G04
The University of Sydney, NSW 2006, Australia
Telephone +61 2 9351 5267
Fax +61 2 9351 3031