# Converting voltage to dB SPL

Hello all,

I currently have a microphone the is outputting voltage values to the Arduino serial monitor.

What calculations would i have to perform on this voltage to convert it to dB SPL?

A calibration curve.

To expand:

Youll need to either find the output voltage vs decibel graph provided by the microphones spec sheet.

OR

Make your own graph using known sound levels and plotting a function/ Look up table.

Have you tried a Google search?

In particular:-

(If) Your microphone has a sensitivity of -46dBV/Pa , this gives 0.005012 V RMS/ Pa 1 Pa (pascal) equals 94 dB sound pressure (SPL)

The dB equation for voltage is 20×logV1Vo

where V1 is the voltage being measured, and Vo the reference level

If we do an example calculation for the measurement of 2.5v (assuming a unity gain for the amplifier) we get

20×log2.50.005012=53.96dB

so the SPL will be (-46) + 53.96 = 7.95 + 94 = 101.95 Db SPL

We assumed a unity gain for the preamplifier, if the actual gain was 20dB then the SPL becomes 101.95 - 20 = 81.95 Db SPL

if the actual gain was 10dB then the SPL becomes 101.95 - 10 = 91.95 Db SPL ...

OldSteve: Have you tried a Google search?