Looking at the graph it's almost certainly USB noise. Have you tried another, better PSU? Alternatively, an extra ripple filter capacitor (2200 uF, 10 V) on the 5V rail could help too. In general, these USB mics have very little power filtering which makes them extremely susceptible to noise on som...

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So, I took a new sample from a video today and one can hear a "click" sound every second which I find wouldn't sound too much alike ground loop noise. Anyway here's a image of the frequency analysis:


Here is the spectrum.txt exported from audacity.

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Using this microphone I have some severe noise in the background. The more peripherals I plug in (camera, gertboard, wi-fi adapter) the worse the noise becomes. We've tried several different power supplies, however the problem still remains. The microphone seems to pick up some switching noise from ...