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I had a question about sound measurement in air using a B&K microphone. In the acquired time resolved sound measurement signal I can see both negative and positive voltages/ pressure values. I was wondering does the negative values associates with the rarefaction events in time at a fixed position in space and correspondingly positive value associates with the compression events ? If this is correct the mean value of the time signal should represents the ambient pressure in the absence of the sound?

  • Voting to close as this question might be better answered on dsp.stackexchange.com (or another acoustics oriented website) – audionuma Apr 25 '16 at 20:27
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A microphone usually measure pressure variation or pressure gradient of the acoustic sound wave at the transducer location. That means that the atmospheric pressure (what you possibly call ambient pressure) does not generate output on a microphone.

What you are actually measuring at the output of the microphone is the acoustic wave pressure oscillating around the atmospheric (quasi) constant pressure.

To measure atmospheric pressure, you need a barometer.

  • @Thanks for your feedback. This means that microphones can actually sense both the rarefaction and compression of air which occur around the atmospheric pressure. My intention was to understand the output signal of a sound measurement system. – Ramin IJ Apr 18 '16 at 12:44
  • @RaminIJ : what is your ultimate goal in these measures ? industrial noise measure ? Room treatment ? Automotive ? Knowing what your intent is might help providing better answers. – audionuma Apr 21 '16 at 10:45
  • I have measured the pressure variation within a1D standing wave in time and space using a 1/8" B&K microphone. I would like to further understand the signal I have acquired. – Ramin IJ Apr 25 '16 at 19:38
  • Your comment makes me think that your question does not fit into this stackoverflow group and might be answered on another one. – audionuma Apr 25 '16 at 20:30

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