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I'm working on a project to absorb sound energy and I'd like to ask for hints, or methods, of calculating the energy received by the microphone, or energy per second (power).

I took measurements using a very sensitive microphone which outputs a voltage to a DAQ card in a PC. Using labview I convert this voltage into Pascals using the sensitivity and pick-up or response of the microphone.

Now I have an FFT of the time trace showing me the amplitude in Pascals (I think...) and the frequency as domain. I'd like to now figure out how I can calculate how much sound energy the microphone is receiving at each frequency. (Then when I add in my acoustic damping I can say and measure the change in peak height at each frequency I can get a number for how much energy I'm asborbing).

I know that energy is proportional to the square of the amplitude, so I can get a "Factor of X decrease" in energy or power. But, I'd like to get an actual number in microwatts or microjoules of what effect this absorption has. I also know I'll have to make an assumption that the sound field is diffuse (or evenly spread). One quick question: pressure recordings should not depend on microphone orientation with respect to the direction of sound waves travelling, since pressure is directionless - correct?

I've tried some dimensional analysis starting with N/m^2, 1/s, and trying to "get" to units of energy, but it feels like there's a lot of different arbitrary paths to get there.

Suggestions, hints, provoking thought experiments, and the like, are more than welcome!!!

Best,

H2bro

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# Calculating power and energy based on frequency and amplitude (pascal)

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