Raspberry Boom Infrasound Monitor

COMING TO KICKSTARTER ON MARCH 22nd, 2018! (This section of the manual is a work in progress. Won’t be finished until April or May of 2018)

Manual

Note

All models of Raspberry Shake, including the Raspberry Shake [1D, 3D, 4D], Raspberry Boom and Raspberry Jam use the same software. Sections of the Quick Start Guide have been tailored to each product but the overall manual applies to them all. Other specific manual sections, like this one, have been created to address issues specific to the individual products.

Installation

The Raspberry Boom is sensitive to temperature but not orientation nor leveling. The Raspberry Shake and Boom, because it has a built in seismometer, must be leveled.

Warning

Do not touch the tip of the mechanical filter! It has an incredibly small orifice (microns in diameter) which would easily be clogged by oils from your fingers.

DIY Wind Noise Reduction Solutions

Also known as “wind shields”.

Wind is the most common type of infrasound noise, especially below 2 Hz. Wind noise reduction is the biggest challenge and biggest impediment to successful infrasound monitoring. It is just part of the game: If you want to measure infrasound, you have to fight the wind! You can get a feel for this by installing your Raspberry Boom outside on a windy day. If you are interested in experimenting with wind noise reduction, you can try any of the following low-cost, Do It Yourself (DIY) strategies to shield your Boom from the wind.

Strategy 1

Take a fake rock or bucket, drill a bunch of holes in it, line it with a porous foam material and locate the Raspberry Boom inside.

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Strategy 2

The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) infrasound network employs spatial wind noise averaging systems like those seen in this youTube video and this article. Create your own spatial wind averaging system inspired by the pros at the CTBTO.

These are also known as “pipe arrays”, “porous hoses” or “soaker hoses”.

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Hint: Fitting the ends of the PVC pipes with a bit of foam dramatically improves wind reduction results.

Some rules of thumb
  • Stations located in dense forests usually have acceptable wind-noise levels at all times of the day
  • The floor of a dense forest is much better than open ground - any wind is intercepted and slowed by the tops of the trees and the branches - well above a sensor on the ground - so the variations in air flow and the pressure changes at ground level are minimized. (Thanks Chris)
  • An obstruction, like a hedge, typically shows wind reduction for downwind distances of up to ~50x it’s height. If you don’t have the time to grow a hedge, Chestnut Palling fencing works quite well - this has ~1” vertical Chestnut wood strips held together with twisted wires, top and bottom. It comes in various heights - note that this is a POROUS obstruction - a flat topped wall may generate horizontal air vortices downwind. (Thanks Chris)

Additional Resources

Some resources if you want to really dive deep into wind noise reduction (Thanks Don):

Sources of infrasound and their dominant frequencies

Infrasound is any sound beneath the audible frequency range of the Human ear (20-20,000 Hz). The Raspberry Boom detects infrasonic sources from ~0.05 to 20 Hz and audible sources from 20 to 40 Hz.

You will be surprised just how many things actually generate infrasonic signals:

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Depending on your geographical location and proximity, you will measure infrasound from different sources. Remember with the Raspberry Shake “Station View” array, you will be able to see activity from all over the world from all the different Raspberry Booms interconnected to our online map! So even if you don’t live in tornado country or on the flanks of an active volcano, you will be able to access data from other users who do.

For me details on sources and their dominant frequencies, download: Infrasound Source Dominant Frequencies Table

Jargon

An infrasound sensor is also known as a “microbarograph” and “pressure transducer”.

Acknowledgements

Developed by the Raspberry Shake team, the idea for the Raspberry Boom was originally inspired by Jeffrey Johnson Of Boise State University, an expert in volcano infrasonics with a Ph.D. in Geophysics, who developed his own infrasound sensor called the InfraBSU.