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Forum Index : Electronics : Infrasound recording/logging
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Dingdoc Regular Member  Joined: 23/09/2009 Location: AustraliaPosts: 76 |
Has anyone else read the SC infrasound detector article yet? It looks like they have done a fair bit of homework on it and I was thinking if anyone else was planning on building one it may pay to have a thread on it to compare notes. The electronics looks fairly cheap to assemble but was disappointed to find that the software was going to be closer to $40 than the $30 quoted in the article. I have started on the "Pre champ" PC board and ordered an LM380 amp board off the net rather than build that part (didn't have the Feb '94 edition to get the board pattern). PS Wasn't sure if this should be in the 'Windmills' section or the 'Electronics' - Glen, please feel free to move it if you so desire. Trev |
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| MOBI Guru  Joined: 02/12/2012 Location: AustraliaPosts: 819 |
Yes, I have had an email or two from Leo Simpson and sent a letter to the editor which hopefully will coincide with the publication. I think this is the right forum as I am not sure where else one would want to measure infra sound, but you never know. I intend to construct one so that I can check on the wind fram operators when turbines are supposedly turned on and off during health effect assessment. Also, I want to be able to log many other homes of those claining adverse effects. I did a bit of playing with a Fast Fourior Transform trial package off the net. It allowed me to record sound using the laptop mic and run the FFT over it to display the frequency and levels of sound down to 1Hz. I intend to get a better mic and pre-amp of some sort and try a plug in mic. David M. |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I moved the topic to electronics. Lots of things make infrasound, not just windmills. And until there is a proven connection between infra sound, ill health, and wind farms, I dont want to tie them together by having a infrasound measuring device sitting in the windmill forum. I'm also concerned the term wind turbine is used too lightly in this infrasound discussion, and dont want to create the impression there is a link between ill health and the small scale wind turbines that make up a large portion of this web site. Many of us depend on our own wind turbines for our energy needs. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Dingdoc Regular Member Joined: 23/09/2009 Location: AustraliaPosts: 76 |
Thanks for moving the topic Glen - I figured you probably would but thought it was OK to start it in the 'Windmills' section as that was where the first reference was made. Perhaps if owners of small mills had access to one of these detectors they could use it to demonstrate that their mills are NOT producing harmful infrasound - I'm sure that as this topic gets more publicity in the media there will be complaints by some people who will use them to blame for every ailment they have! As far as sources of infrasound are concerned, the list is almost endless with the ocean being one of the major contributors - so much for major population areas being near the sea, but as they say "Oils ain't oils". It's all to do with sound pressure levels, frequency and duration. David, I would be interested in having a look at the FFT program if you could provide a link to it. Trev |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
Yes, I agree Glenn, that is why I refer to the big fellas as what they really are i.e. "Industrial Wind Turbines" The acoustician who tested our house also tested the 500watt OEM turbine we have and it produced no measuarable Infrasound and the audible component was down in the noise floor. @Trev. I haven't had much of a look at what the software will do because I don't have good audio to play with (yet). Have a look and see what you think. http://www.nch.com.au/wavepad/index.html David M. |
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| Dingdoc Regular Member Joined: 23/09/2009 Location: AustraliaPosts: 76 |
David Had a look at the website but have not downloaded the program yet to trial. Did you have any reason for choosing this particular software and how does it compare feature-wise with the suggested Fatpigdog program which is cheaper? I have built the Prechamp board and had a look at the output on the CRO - rather amazing to see the sensitivity of the 'junk box' mic. With the low pass filter switched in I can see it picking up low frequency infrasoud quite readily. A visible response can be seen by jumping lightly on the floor or gently flexing the wall of the room. Waving your hand in front of the mic also has an effect. All probably around the 1Hz region The next step will be to see how well it drives the sound card - a quick check did not look too good but the sound card could be a bit dubious. I also intend trying to use a Pic(axe) to digitize the output and possibly record and analyse it using something like the Amaseis program which was designed as a seismic data recorder - depends on it having a fast enough sample rate. That way the results could be recorded as a real-time display and I think it also has a FFT function. The trouble is these things all take time which is in short supply at the moment - too many other projects on the go as well! Trev |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
I picked the programme because it was the first reasonable one I found when looking for FFT software. Compared to FPD, I don't know at this stage. I need to have a play too and as you know, time is hard to find. I suspect though, that FPD will work in real time and the other might only be able to run over pre-recorded data. Not sure. The acoustician who did the ISound monitoring of our home is also playing around with Maxi and Duino Mites to digitise and log the data - plans to make up low cost units that can be posted to site, and switched on. No more for the recipient to do. I don't know how he is planning on digitising the data as the MM, Picaxes etc can only do 10 bit (1024 resloution) and I don't know if this will be sufficient to look at the audio spectrum - maybe is only planning on infra sound end.??? Out of time - back to work  David M. |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
You could try using "Audacity" which is a free audio recording software and some tests i done in the past showed it can record to low frequencies and allows for post filtering to be done if needed. I have also used the seismic recording software "AmaSeis" in the past, and its Ok but not great, also be very careful with the downloads of it as there is virus in some downloads, save to file and run a check before installing it. Pete. Sometimes it just works |
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| Dingdoc Regular Member Joined: 23/09/2009 Location: AustraliaPosts: 76 |
David I would have thought this would be sufficient - is there any reason for logging the the whole spectrum? Pete Thanks for the warning about Amaseis - I will be sure to check it first. Regarding digitising the IS spectrum, a browse of the web uncovered Arduinoscope which may be useful. When I get a chance I will look into this as I recently bought a Uno board to see what Arduino is all about. Trev |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
I just got an email from the acoustician who has built the SC infra sound meter and his description of the performance wasn't very flattering. He is only monitoring the 1 to 20Hz band as that is the main focus with respect to turbine related physiological problems. The audible spectrum is already "fairly" well known. The 4th order Bessel Filter plot he showed me cuts off pretty sharply at 20Hz. He thinks also that 10 bit AtoD is enough, but if not is going to use external higher resolution AtoD and use the MM or DM as the data logger only. I'll keep you posted as he keeps me posted. David M. |
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| Dingdoc Regular Member Joined: 23/09/2009 Location: AustraliaPosts: 76 |
What was his main criticism - was it poor sensitivity or S/N ratio? From what I have read on IS recording, the biggest problem can be wind noise. I felt that this would also be a problem with the SC design and wonder if it can be improved by using a wind filter consisting of an array of 'leaky' pipes. It also seems that multiple paralleled microphones can reduce the signal noise. I can't find the links to these just now but will look and post if anyone is interested. As far as the SC project is concerned, it's a big ask to do something like this in view of the expensive equipment used commercially and I feel they have done their homework very well in coming up a setup which is both cheap and has some calibration, even if not lab quality. It should give users a good starting point into an otherwise relatively unknown field. My interest in it arises from the fact that my brother lives near a commercial wind farm, although he seems to have no ill effects from it, possibly due to distance. I would be curious to see what sound levels he receives and what the IS spectrum looks like at close range. Trev |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
From what I gather, the LP filter lets way too much higher frequency noise through clouding the IS. I asked if it was worth building the Champ system to hook up to a CRO and was told not to bother, but I think I will anyway just to see if I can "see" acoustic energy waves at around blade pass rates. The acoustician has designed a 4th order bessel filter (in hardware) and is waiting on the parts, then he has to build it, so I mightn't have much to report for a few days. Mind you, if you find out more, fell free to chuck it at me. Meanwhile, I've been reading up (refreshing) on software (C++ etc) that performs FFTs. I have been considering using a dsPIC that can do FFTs - need to read up on that too. A hardware FFT would be much faster than software unless the FFT was done on a PC perhaps? David M. |
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| Dingdoc Regular Member Joined: 23/09/2009 Location: AustraliaPosts: 76 |
Just an update on the IS detector project. Now that the preamp seems to be working and the CRO is showing a useable output I figured it is time to start looking at analysing the output. Rather than spend the money straight away on the Fatpigdog analyser software I did a search on the web for alternatives and found one called Visual Analyser - Visual Analyser (This freeware looks to have some other interesting features like a sig gen, audio frequ measurement and component testing which I plan to look into when time permits) I downloaded & installed this on the other Windoze XP computer (without too many obscene utterances about Microsoft and slow computers) then connected the IS mic/preamp to the mic input of the soundcard. After a bit of playing around with soundcard settings I managed to get outputs displayed on the CRO and analyser screens. Admittedly I took some time to get a very basic understanding of the software and how to drive it and the display was somewhat 'clunky', but at least it was showing a signal. The spectral display lacked resolution at the low end but I played around with some of the settings and improved it a little - it would have helped if I knew what I was doing but at least it was a good learning experience. The spectral results also seemed to back up the acoustician's criticism of the LP filter cutoff on the preamp. I feel that feeding very low frequencies into a soundcard is not doing much for sensitivity at the bottom end of the spectrum and hope to look at ways around this in the future - either an a-d converter or a soundcard mod. At the moment its all about learning and experimenting. Trev |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I must have a look at the Visual Analyser link, i was intending to use Audacity for a pre test, it can be found here for free. AUDACITY At present i have not got to build a board up yet, although i have done a PCB layout for the Pre-champ and added a 9v reg to the board, as i hate needing to use a 9v battery in projects, because its an odd voltage for me with most electronics i do. (a plug pack is far easier and greatly cheaper) Once i have constructed a working board, then i will post the PCB artwork should someone else wants to knock a board up. Pete. Sometimes it just works |
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