Calculate Decibel by Amplitude - Android Android Recorder

Question

How to calculate decibel from maxAmplitude, I wrote an Android application to get maxAmplitude at regular intervals, I need to show o / p to the user in decibels.

Answer 1

decibels are relative units, they express the power of your signal with respect to some reference power.

If you work with amplitudes, then the formula:

power_db = 20 * log10(amp / amp_ref); 

(See http://en.wikipedia.org/wiki/Decibel#Field_quantities ).

Note also that maximum amplitude is usually not a very good indicator of volume (or even power). Generally, you should measure the RMS power of your signal and convert it to dB instead.

Answer 2

Regular telephone microphones are not calibrated to measure absolute volume, so this is not possible without using a sound meter to calibrate the phone for the first time. As Olya mentions, you can calculate the relative change in volume, but I expect you to want to play a real sound level meter.