Faber Acoustical Forum

Faber Acoustical iOS Apps => SoundMeter => Topic started by: mgolden on August 28, 2017, 01:10:13 PM

Title: Calibrate MicW i437L
Post by: mgolden on August 28, 2017, 01:10:13 PM
I hope someone can help.  I just got one of MicW new i437L microphone with a lightning connector. This seems to be a digital microphone which I have not really used before.  The unit comes with a tested sensitivity of 24.8 Pa/FS.  The nominal sensitivity on the datasheet is -27.5dBFS (94dB SPL @ 1kHz).

In the input options of the I/O Configuration I have set the Device Units to "FS" and the Gain at "Mid".  Under Input Channel menu, I have set Units to Pa and entered in the tested sensitivity.

It is the gain setting that I am not sure of.  Changing gain changes the SPL.  Mid seems to give the result that is closest to what I think the measurement should be.

Next time I am near an acoustic calibrator I plan on checking the calibration. 

Thank you in advance.
Title: Re: Calibrate MicW i437L
Post by: FaberAST on November 27, 2017, 04:50:01 PM
Unfortunately, the i437L presents itself as if it were a standard headset jack. This means that apps like SoundMeter cannot automatically distinguish between an i437L and a standard headset jack.

Your approach is correct (i.e. Device Units = FS, Channel Units = Pa, Gain = Mid). We do not know the precise input gain used by MicW when testing the sensitivity of the i437L, but using the Mid gain setting in SoundMeter seems to work well.

It's too bad MicW didn't take advantage of the opportunity to produce a digital microphone that presented itself uniquely to iOS. That would have allowed automatic loading of sensitivity information, similar to what SignalScope does with the Digiducer digital accelerometers.