Quote:
Originally Posted by jacko  In theory to absorb a wave we need a porous absorber that is 1/4 wave length deep. Why fiberglass panels absorb lower frequencies? My panel is 8" deep (6" fiberglass spaced 2" from the wall). It should absorb frequencies down to 425Hz (8" is 1/4 of a 425Hz wave length) but in fact it is very effective down to 60Hz. Could someone point me to some documents where it is explained? |
It's not that an absorber should be 1/4 wavelength thick but that it should be
positioned at 1/4 wavelength from the wall.
What's important is for the wave to pass through the absorber, which can be
of any thickness. The 1/4 wave bit is just that at that distance from the
wall the velocity of the wave will be at its highest so it's the best place to
stick your absorber.
Paul P