Weird Helicorder Patterns

Hi! We currently have a Raspberry Shake 4D on our classroom, although we’re planning to install it on an underground vault. We’re getting some weird patterns on the helicorder image when there’s no students in the school. It seems to repeat every 15 minutes or so. Does anyone have an idea of what this could be? PS. There’s a WiFi router in the classroom, just in case this could affect it in that matter.

In this case it is very useful to have the spectrogram handy. If you haven’t already done so, you should install SWARM so that you can have a better look at your data. My guess is that this is from an HVAC system, or maybe a pump or fan of some sort.

Here’s a spectrogram of one of these periods overnight last night at RDDB2, with a little earthquake as well. You can see that whatever is making this noise is doing so at almost exactly 35 Hz:

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Hi! Thank you very much for your response! Yes, we have Swarm but are still in the process of understanding its features.

Ohh ok, now I’m understanding the spectrogram more or less. I will check the area for any fans or pumps, maybe it’s one of the school’s HVAC system that runs 24 hours. I’m thinking that when we build the underground vault this noise will be considerably lower, since it will be 100 feet or so away from the structure.

Once again thank you for you help, we will look into analyzing the spectrograms for the different cases!


Cheers. Here’s an annotated version:

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