I wonder if it is theoretically possible for the RBOOM to pick up micro-baroms ? During some quiet stretches this morning my unit picked up traces of something in the expected frequency range (0.2-0.3 Hz).

window size: 64 seconds
number of FFT points: 8192
overlap: 95%
power range: 100-160 dB
min freq: 0.05 Hz
max freq: 1.0 Hz

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Very nice spectrogram. I would argue yes, it is absolutely possible. Can you check against any other infrasound instruments in your area to ensure it’s not some local atmospheric disturbance? How far are you from the ocean?

Well - here is one about 50 km away, also from last night. A bit more difficult to tease out the image (this is a 50 s/sec unit)

I am >100 km from the ocean. We do have a breeze blowing from that direction today though.

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Infrasound can travel a surprisingly long distance in the atmosphere. My guess is that’s real.

I am reserving judgement on this one. In the meantime, I have procured some metal plugs that can completely seal my rosette system and next time I see the 0.25 Hz “signal” I will go out and plug up the system and see if that signal goes away. Meanwhile, it has become very quiet overnight. The screen shot below is what the ambient noise floor look like down to 0.05Hz (20 second filter in use).

Comparing this to the previous picture, you can see an increase in the background noise starting at about 0.4 Hz but nothing like what I was seeing before (same gain settings).


My guess is just a guess based on limited evidence, and would require a lot of further testing to be more than that :slight_smile:

Very nice quiet signal!

OK - here is part 2.

Today I noticed (somewhat belatedly) the 2.5 Hz signal again - both here and at the other station 50 km east of here. So I rushed out and installed the metal plugs on my system and ran it for a while “plugged up”. The 2.5 Hz signal did, in fact, go away as you can see below. What remained is some signal between 0.01 and 0.1 Hz - increasing in amplitude with decreasing frequency. I figure this is either system noise, or possibly leakage right through the walls of my rosette pipes. They are solid black-iron pipes, but I have learned that infrasound can do weird things. Any way, I unplugged the pipes just in time to see the signal still was there … but fading out and being replaced by another growing up from about 0.02 Hz … no idea what that one is.

With hurricane Dorian coming up the east coast, there could be some interesting infrasounds. The problem here will be if we get an easterly wind - that is a direction where my RB does not have much shielding and the wind noise will dominate…


OK - so the hurricane has passed by and is moving away from us.
I am seeing really good 0.2 Hz SNR on the RBOOM