I know I can get the visible absorption spectrum of water, but how does one go about getting and testing what the absorption spectrum is for a glass of water in the audio range of (0hz to 20000hz)? I know nasa uses water to absorb sound. How can I measure what the sound absorption spectrum is in a glass of water?
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Why a "glass of water" ? If the sound is created outside the glass, you have to deal with two interfaces: air-glass and glass-water. If the sound is created inside the glass, are you simply looking for absorption/decay over an unbounded range of water?
Setting up experiments to measure the absorption would require at the least some high-quality hydrophones and an Olympic-sized swimming pool. I don't recommend trying to reproduce what's been done by scientists with bitchin' gear.
That said, a simple LMWTFY finds this calculator for seawater, and a stack of formulae for fresh water.
answered Feb 2, 2017 at 13:00
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1$\begingroup$ The second link is for calculating the speed of sound, not the absorption. Just to add a bit (given the vagueness of the question): if you're talking about just how loud a sound is after travelling through water, you'd also need to take into account the inverse square law. And in a glass, you'd also have to deal with almost infinite reflections and their associated phase-cancellation, meaning that for any given position in the glass it'd be almost impossible to calculate the exact amplitude of a given frequency... $\endgroup$ Commented Feb 3, 2017 at 0:19