I'm using an inexpensive seismometer to try and measure the effects of local HGV traffic on buildings. The device is connected to a Raspberry PI that has a Cirrus Logic Audio Card. The signal is fed through the Line In. I am saving the readings from the device as a WAV audio file via arecord:

arecord -c 1 -f S16_LE -r 11025 --max-file-time 86400 --use-strftime %Y-%m-%d_%H:%M:%S.wav

It works, I can normalize the WAV file in Audacity and see the waveform change as a HGV drives past. After reading a few articles about other experiments doing the same I see that I need to convert the readings from the device into Peak Particle Velocity (PPV) and Vibration Dose Value (VDV) for any of it to make sense in terms of ISO/BS standards (BS7385 & BS5228-2 for example) and assessing the likely effect on a structure of local traffic vibrations.

That's where I get unstuck, how to convert the waveform data I have into PPV / VDV?

This is therefore a question of how to interpret the WAV waveform data into units that relate to the effects if vibrations from local traffic on buildings (humans)

I don't know about a few things, like whether the the arecord sampling frequency and depth are correct, I probably shouldn't be normalizing waveforms in Audacity (i'm only doing that so I can see if it's working).

I do know that I am looking for frequencies between 15 and 150Hz 9hz to 15Hz and that I think I need to get my units into mm/s. My experiment isn't exactly scientific from the Lego Seismometer, a starting point for possible future more detailed data collection and analysis is all that I need.

Edit:

The Lego Seismometer says it works in the frequency range 1-2Hz up to 25 Hz. It is a commercial product based on a design from the British Geological Survey. The device is meant to be used as an educational tool and as such I can't imagine it's very accurate/calibrated but compared to professional commercial geophones it's more accessible from a price perspective.

I have previously tried using Mindsets Slinky and the EnviroPhat (using the LSM303D accelerometer). I had a hard time making sense of the accelerometer data.

Here are some papers I found:

http://www.saveourstreets.co.uk/docs/3_AnAssessmentoftheImpactofRoadTrafficVibration.pdf

The above is the most interesting and most closely matches what we're trying to do and it cites the British Standards they used in their analysis and those are the standards I am referencing below

BS6472-1 - Guide to evaluation of human exposure to vibration in buildings. Part 1: Vibration sources other than blasting

BS7385 - Guidelines for the measurement of vibrations and their effects on structures (UK implementation of ISO 4866:2010 - supersedes BS7385-1)

BS5228-2 - Noise and vibration control on construction and open sites

The below are additional papers I found which were interesting and backed up the assumptions from the above first paper.

https://www.witpress.com/Secure/elibrary/papers/SD95/SD95062FU.pdf

https://jcaa.caa-aca.ca/index.php/jcaa/article/viewFile/627/329

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.509.3322&rep=rep1&type=pdf

Transport Research Laboratory - https://trl.co.uk/sites/default/files/SR402.pdf

Note that as this is a homebrew experiment I don't have access to commercial grade analysis software. I am on Linux and comfortable with PHP/Python/MySQL/Bash.

This question has also been posted on Earth Sciences and the DSP SE as well as a detailed thread on using Raspberry for seismic observation.

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    It would be useful to have a link to one of the articles you read describing similar experiments. Also, could you provide more details about your home-made seismometer, its calibration and output? – sammy gerbil Jun 27 at 15:56
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    I think this is a good question, but some editing would help you to attract better answers. It's not clear on a casual reading whether this is a question about seismology, or about data acquisition, or about data reduction, or about interpreting your measurements using the language of acoustics. I think it's the last of those, which does make it a good fit for us, but you could make that clearer. – rob Jun 27 at 16:20
  • I don't know the right way to do this for ISO standards, but particle velocity is just the derivative of your displacement signal, and the acceleration is the derivative of that. – HiddenBabel Jun 27 at 18:25
  • I think you need to understand what the output of your seismometer represents. The Lego spec says default gain is 0.64uV/count, but what is being counted? – sammy gerbil Jun 29 at 10:09
  • @sammygerbil where did you find that figure? Are you reading the USB Digitizer spec? mindsetsonline.co.uk/shop/seismometer-interface-usb Because i'm not using their device to convert the signals, I'm using the Cirrus Sound Card – tringwebdesign Jul 2 at 17:33

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