RBOOM install advice

#1

I see that big installations of infrasound sensors tend to use various sorts of arrays of pipes (or hose) to reduce pickup of wind noise and other unwanted sounds. Is there any benefit to doing this with the RBOOM? and how would you do it? (has anyone done it?)

Revision (found the instructions!) https://manual.raspberryshake.org/boom.html#extension-tubing

But still interested in the discussion …

Ken

#2

Hi Ken,

There are several ways to do this, from simply extending the tubing away from noise sources, to quite elaborate solutions like @jochen.richert’s infrasound array seen here: http://wetter.richert.ch/infrasound/infra-details.html

The benefit is that you get less anthropogenic or wind noise and cleaner atmospheric pressure fluctuations. It’s similar to installing a Shake away from a house in order to isolate it from people walking around, for example. Perhaps someone from the community can comment more fully than me.

Ian

#3

hmmm - not much discussion. It seems to me that you need to limit any pipe array (“rosette”) to 3.4 m radius in order to avoid a resonance near 50 Hz. I have seen some larger ones in online papers, but they were looking at lower frequencies. I would guess that PVC pipe would itself generate noise when stimulated by wind or rain so that something heavier would be better (as shown in your link). Either that or protect the array from wind and rain (not easy - unless perhaps buried, but then it would pick up seismic activity).

#4

Ken:

Buenas tardes.

You probably saw this already but we provide some recommendations and links to additional resources here.

branden

#5

Yes, thanks, this is the same as the link in my revised text of May 30. One question I have: I intend to mount the RB in a diecast metal box for RF shielding. After some thought, it occurs to me that I really should put the filter tube inside the box to avoid extending the effective length of the filter tube and changing the time constant. So the box will need a vent hole - which is undesirable for outdoor use…

On the other hand, if I double the volume of the tube between the RB and the capillary orifice by placing the filter outside the box, all it would do is double the time constant to ~2 seconds (in the case of the 1 second filter). I would be happy with 2 seconds.

What is the consequence of telling setup that I have a 1 second filter when, in fact, it is a 2 second filter?

#6

Ken:

Buenas tardes.

Please send me a photo of all filter parts when they arrive and I will annotate it to explain things a bit more.

Yours, Branden

#7

It occurred to me that since there is some tubing after the orifice I can just connect that to a port going outside the box. Photo below shows the box and the bulkhead feedthroughs that I will use. I just need to make sure I can curl up the tubes inside the box without kinking them. The non-filter port will go to the pipe array and the filter will just have a bug screen on it. This metal box will go inside another (plastic) box for rain-proofing.

#8

Both ports should be joined/ go to the same pipe array.

branden

#9

aha!
Thanks for that.
So the little black gizmo in the instruction photo is a sort of T fitting or manifold… I guess the connection is required for the high pass-filter to properly cancel signals below cutoff.