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?
Here is the FFT spectrum of a silent room:
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.
Hi, what type of tool do you use to plot audio FFT?
I think I used Audacity. That’s the Mac version, but it’s cross-platform and free.