Originally Posted by Ethan Winer
It's tough to imagine any absorber that could shift even 20 percent let alone 300 percent!
The larger difference here is the speed of sound inside
the absorber instead of outside. Edit: Also FOH was mentioning speed, not frequency.
If you think about light passing in and out of water:
It travels at the speed of light through air
Hits the water, slows down, bends
Leaves the water at the speed of light again, bends back, amplitude has been decreased due to absorption and reflection.
However, the frequency of the light wave is the same inside and outside of the water, so my previous description actually does not
explain the shift in frequency of peaks.
As per the law of conservation of energy, light (or sound in this case) is slowed down in speed and in frequency, but only inside
the water (or porous absorber).
The only thing that really changes is the phase and the the position.Edited by GIK Acoustics - 3/9/13 at 11:56am