Eliminating background noise on MEMS microphone

Hardware
1

Hi all,

I have an ADMP401 MEMS microphone + (66 V/V gain) opamp from SparkFun connected to a Photon and streaming audio over the web using @rickkas7 library.

There is some low frequency noise (<100Hz) coming through… any ideas what this might be? Antenna effect picking up 60Hz? Noise from the voltage regulator?

Also, when the USB power is plugged in, there is a higher frequency harmonic (1kHz) coming in…

Do you think adding some bypass capacitors at the power lines (1.0uF?) will help clean this up?

Thank you!

Here is the FFT spectrum of a silent room:

Pasted image1356×954 51 KB

2

I’m glad my code worked! I had disassembled the circuit I used, but I still had some recorded samples saved. I was connected by USB and didn’t get the 1 kHz noise, but I did have some low frequency noise. Some of that was probably air conditioning noise. I’d give some caps a shot; no harm in doing so and it might help.

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3

Hi, what type of tool do you use to plot audio FFT?

Thanks,

4

I think I used Audacity. That’s the Mac version, but it’s cross-platform and free.

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