You're on the right lines regarding the wavelength of the waveform. With longer waveforms
there's more power, this about the meters on a mixer - it's takes a lot less bass to get
them to peak than any other frequency. It also depends on the thickness of the
object/wall. A good approximation is that you need something at least a quarter of the
wavelength thick to absorb sound at that frequency.
wavelength is approximately (off the top of my head) about 3.6 meters long. Therefore to
absorb 80Hz you would need an object 0.9meters thick.
It then all depends on
how the wall/surface is built - if there are any holes or vents then the sound will escape
through that - think about the difference between double glazing being opened 0.5cm and
shut - loads of sound comes through when it's only opened a tiny bit.
there's the material's absorption co-efficient - different materials absorb different
frequencies at different rates.
Hope this helps a little.
hundreds of books out there that go into way more depth, but it's a field that people make
a career out of so you can see the scope!
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