# Volts to decibels using microphone's transfer function

I'm attempting to convert a voltage signal originating from a microphone to decibels. However, I do not have the "microphone sensitivity" in terms of dBV/Pa which is used in this previous conversion. Instead, I have the microphone conversion factor as sensitivity.

Given the details below, how would I go about converting this voltage to decibels?

Approximate sensitivity: 250mV/Pa

Pre-amp gain setting: 12 dB

Approximate input-referred self-noise Level (bandwidth: 30-50 kHz): 18 dB SPL

• how are you planning on calibrating the decibel readings? – jsotola Feb 5 '18 at 21:11
• I wasn't planning on calibrating the microphone myself, although I could. My crude understanding was that if I had the microphone's sensitivity rating in terms of the voltage output for a given pressure on the microphone, I could get back to a decibel reading. From previous posts, this seem like it should be the case, but am I wrong about this? – E. Camus Feb 5 '18 at 21:22
• Remember that decibels are a differential reading, though some have assigned ref points such as 130 dB for a jet engine, etc. – Sparky256 Feb 5 '18 at 21:33
• @E.Camus, are you aware that 250 mV is equal to -12 dBV? – davidmneedham Feb 5 '18 at 21:38
• @davidmneedham I assume you are getting -12 dBV from 20*log10(0.250), where 0.250 is the sensitivity in terms of volts per pascal? If so, how do I use this to calculate a reference voltage so I can use the somewhat standard decibel calculation, 20 * log10 (V/Vref)? – E. Camus Feb 5 '18 at 21:53