iMM6 - Background noise

[pa sk]

Hello all!

Could you share the spectrum of the quiest environment you were able to measure?

By "spectrum" I understand the octave measurements which are gathered during Leq measurement.

I use the iMM-6 mike with calibration file applied and additionally "Cal. Offset" is set using standard +94 dB 1 kHz audio calibrator as a reference. The result I got looks quite noisy to me and I wonder if it is due to my phone, mike or maybe something else.

My results (flat, tleq = 10 s, det. = medium, resolution = medium):

Paweł S.

[pa sk]

Anybody?

[Julian Bunn]

Hi Pawel,

It might be interesting to measure the spectrum with the mic input shorted, so that all you measure is the internal noise spectrum of the audio input (ADC etc.) of the phone.

Julian

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[pa sk]

Of course you are right Julian - I should have included that characteristic too, especially that I had it already measured then.

That said, here is the complete graph:

Interstingly, measured background noise characteristic, corrected by the internal circuitry noise, is very close to 1/f noise spectrum up to 4 kHz (for 8 kHz and 16 kHz values are too close to each other to give reasonable results, and even 0.2 dB difference in any of the values changes the graph drastically, so I would risk and say that that 1/f-like slope is valid also for that higher range ).

Anyway, I am asking again if anyone could share some background noise measurements.

Has anyone done such measurements at all?