Mysterious 30 Hz signal

Hi RS Forum

I moved my RS to a new location and there is now a persistent 30 Hz signal in the spectrogram
day and night.
What would produce 30 Hz?
How can I get rid of it?
Please see attached:

Most likely an electric motor, or some device driven by one (assuming you are in a country with 60Hz power).

As for getting rid of it, I see two options: 1) Find the motor and turn it off. 2) Put your Shake somewhere else.

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Hello rmurawsk,

Yes, as Philip said, that is clearly something relatively close-by which is always on (at least for the duration of the spectrogram window).

If you cannot find anything in your house, then it may be something in a neighbouring one, so you can experiment with different locations in your home to see and find the one in which this constant noise is absent, or, at least, minimized. It would be an interesting “hunt”.

Let us know what you discover, as it could be useful to other Shakers in the community!

Yes, US AC at 60 Hz. So it suspiciously looks like a sub harmonic.

Would a make shift Faraday cage help, maybe?

I am checking out new locations for a quiet spot.

Thanks for the reply.

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Hi Stormchaser,

I am currently trying out different spots on my campus looking for the least noisy.
I found a quiet noise level (mostly yellow on the Station View Map), but it introduced this 30 Hz signal.
Must have placed the RS near a mechanical room.

Thank You.



I think that is vibration, not an EM signal. Probably a synchronous motor.
When I first installed mine I thought I had an ideal spot, but was just not aware how far the vibration from the heat pump and air handler motors travelled.


You’re very welcome rmurawsk, I agree with Philip about that 30Hz signal being generated by some kind of motor.

For example, I have a similar waveform on one of my Shakes at around 37Hz, which is generated by the external cooling fans of my laptop.

But, if you want to test a Faraday Cage, one of our Shakers has created an RF-shielded vault that maybe can inspire you: Amateur Radio & My RF Shielded Raspberry Shake Vault Experiment