Calibrate MicW i437L

mgolden

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.

benfaber

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.

stenand

Hi mgolden,

just bought the same mic and I'm curious to know if you ever came around to check your calibration?

Best

benfaber

According to MicW's current instructions, you should set the device gain to Mid and the device units to FS. Then, set the sensitivity for the input channel according to the value that was written on the sheet that came with your i437L (e.g. 19.9 Pa/FS). (Make sure input channel units are set to Pa.)

We just tested this, today, with an iPhone X and XS Max, and the results agreed within 0.1 dB of a 94 dB field calibrator on both devices.

Keep in mind that the sensitivity given by MicW is valid for the Mid gain setting, only. If you want to measure higher or lower SPLs which would require Low or High gain, respectively, you would need to perform a calibration at the chosen gain.