I am using the MAX4466 microphone amplifier to calculate the db SPL level of sound. I have obtained the peak to peak amplitude in volts and I know that the microphone sensitivity is -44 db which translates to 0.0063096 V/Pa. 1 Pa is 94 db SPL.
so, say my voltage reading is 1.7 volts ; in db it = 20 log (1.7/0.0063096) = 48.6 db
Now acc. to a formula I found on this thread How to convert Volts in dB SPL
to calculate db SPL, I must add the mic sensitivity + 94 db SPL i.e 48.6 + 94 - 44 = 98.6 db SPL.
I don't completely understand why we do this?
Secondly, this formula is for unity gain. I don't know the gain of my device to subtract from the db SPL level and I can't seem to find this anywhere. Please help!