title: How to calculate microphone audio input power in decibel unit
body: <p>Please help me calculate decibels from phone microphone. The microphone has a <a href="http://developer.android.com/reference/android/media/MediaRecorder.html" rel="nofollow"><code>getMaxAmplitude()</code></a> function. How I can I use it to calculate decibels? I read in some forums that the decibel calculation formula is <code>power_db = 20 * log10(amplitude / reference_amplitude)</code>. But I don't understand how to find the <code>reference_amplitude</code>.</p>