Hi I've recorded sound(field sound) using six microphones with sensitivity 5mv/pa by zoom recording device the results were obtained by dBFS unit and i need it in dBSPL, Is there any way to convert it? because I have read several articles and come to the do not directly convert between the two units and need to calibrate the device and determining the gain, but I recorded directly without doing anything . Another question whether the output values of positive values and negative do it represent the pressure deviation? I'm sorry but I do not have sufficient knowledge with the sound recording instruments. thanks
You could try to go back and retroactively "calibrate" your original recordings. But that requires these things.
- FIXED RECORDING LEVELS Your original recording must have been done at some FIXED and unchanging recording level/gain from beginning to end. If you changed the recording levels at one or more points during the recording, then you have no way that any of the next steps will make any sense. Note this includes using any kind of "automatic gain" as that completely destroys your data.
- REFERENCE SOUND You need some sound that was captured in the original recording which you can RELIABLY REPRODUCE. That gives you the "link" between your original recording and something that you can actually MEASURE.
- SPL METER You need an actual, calibrated SPL meter. There is no substitute for this if you want believable SPL data.
- CALIBRATED REFERENCE MEASUREMENT Reproduce your "reference sound" and measure the SPL with the calibrated SPL meter. Then you can use that peak level to measure against your recording levels.
Unless you calibrated the microphones AND the recorder at the time of the recording the absolute dB SPL reference is lost and unrecoverable. The reason is that you don't know what what the REAL sensitivity of the microphones are. "5mv/pa" is only the nominal design target. It does not necessarily represent the ACTUAL sensitivity. And only calibrated instrumentation microphones have a known and reliable SPL to voltage output ratio.
Furthermore, you used some unknown amount of gain in the recorder. So even if you had calibrated microphones, you would have no reliable reference unless you calibrated the microphone preamp gains and the recording levels.