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POGet decibel values whilst recording sound?
 

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  1. POGet decibel values whilst recording sound?
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    <p>Is there a way of getting the decibel value of sound whilst it's being recorded? I'm using <code>MediaRecorder</code> to record the sound at the moment</p> <p>I can't use any applications on the Marketplace as I can't be sure the user will have it installed on their phone e.g. Audalyzer</p> <p>I'm using the following formulas but not sure if they're correct or if my results are correct!</p> <pre><code>short data[] = new short[bufferSize]; read = recorder.read(data, 0, bufferSize); double p2 = data[data.length-1]; System.out.println("p2: " + p2); double decibel; if (p2==0) decibel=Double.NEGATIVE_INFINITY; else decibel = 20.0*Math.log10(p2/65535.0); System.out.println("p2/65535: " + (p2/65535.0)); System.out.println("decibel: " + decibel); </code></pre> <p>Current results: </p> <pre><code> 01-11 16:43:03.821: I/System.out(14530): p2: 0.0 01-11 16:43:03.821: I/System.out(14530): p2/65535: 0.0 01-11 16:43:03.821: I/System.out(14530): decibel: -Infinity 01-11 16:43:03.911: I/System.out(14530): p2: 0.0 01-11 16:43:03.911: I/System.out(14530): p2/65535: 0.0 01-11 16:43:03.911: I/System.out(14530): decibel: -Infinity 01-11 16:43:04.001: I/System.out(14530): p2: 0.0 01-11 16:43:04.001: I/System.out(14530): p2/65535: 0.0 01-11 16:43:04.001: I/System.out(14530): decibel: -Infinity 01-11 16:43:04.091: I/System.out(14530): p2: 0.0 01-11 16:43:04.091: I/System.out(14530): p2/65535: 0.0 01-11 16:43:04.091: I/System.out(14530): decibel: -Infinity 01-11 16:43:04.191: I/System.out(14530): p2: 0.0 01-11 16:43:04.191: I/System.out(14530): p2/65535: 0.0 01-11 16:43:04.191: I/System.out(14530): decibel: -Infinity 01-11 16:43:04.281: I/System.out(14530): p2: 0.0 01-11 16:43:04.281: I/System.out(14530): p2/65535: 0.0 01-11 16:43:04.281: I/System.out(14530): decibel: -Infinity 01-11 16:43:04.371: I/System.out(14530): p2: 0.0 01-11 16:43:04.371: I/System.out(14530): p2/65535: 0.0 01-11 16:43:04.371: I/System.out(14530): decibel: -Infinity </code></pre>
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    1. COI assume you are trying to get the signal level in dB? In this case, 0db is the maximum, and everything else is negative. However, if you are trying to measure SPL, this is impossible. Your application is not aware of the microphone, gain structure in the audio device, etc. You would have to provide your own calibration method.
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    2. COIf everything else is negative how do I get a valid dB value from that?
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    3. COit *is* valid, but isn't sound pressure level... rather, it is the signal level relative to nominal (0dB, the highest representable signal level). Sound pressure level measured in dB is entirely different than signal level measured in dB. Measurements in dB are just measurements relative to something else. Again, without calibrating the microphone/device, you cannot convert from the signal level to SPL.
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