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Old 18th June 2009
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The design of a modular sound absorber for very low frequencies

i get the feeling that our method on this forum favours "porus absorbers" (as bbc refers to them) and a couple of types of diffusers exclusively... i am sure there are many, many possibilities we are not paying attention to...

I hope I am not violating any copyright laws... the title of my post is straight out of a bbc paper, pointed out to me by a member here (thanks avare...)...

if i am correct, it suggests that "porus absorbers" (exposed insulation materials... OC703, OC705, rockwool, whatever?) are most effective at frequencies over 120 Hz (or more)... to tackle deep bass in the range of 50-100 Hz, a membrane trap is suggested... bbc's working model seems to be 8" of "supawrap 600 loft insulation" stuffed into a box of 184 mm depth (slightly less than 8", so the insulation is compressed and directly in contact with the membrane...?), with sides and back of 9.5 mm plywood and front of 3.2 mm hardboard...

i hope this is of use to somebody... i invite discussions on whether and how this would work in reality...

jai shankar.