Wednesday, November 12, 2008

Infrasonics Driving You Nuts

I've been reading a lot about sub-30 Hz pulses driving people nuts. I first read about it with the wind turbines, and now someone has written to me about a hydro line.

You are not nuts, people!

Naturally, if you complain to the 'man', you will get contempt, because that is what they do. But I've been involved in noise testing for seismometers, and have found some horrendously powerful sources, that can't be immediately explained. They are most likely industrial. But, one of the biggest noise sources was the hydro tower system. These things sing in the wind!

So what to do? I would really like to form a company - Harold's Sonic Busters, but that sounds too much like work. Anyway, all we would have is a beat-up old seismometer. For hydro lines, the key is to 'detune' them with weights. This is done all the time on the big lines.

However, I am now going to look into the concept of a sensitive seismometer for the masses. If anybody has any ideas, let me know. For infrasonics, we may need a resonating element for the seismometer, like a balloon creates felt vibration with sound. Probably need a really big balloon for infrasonics! I know that Western U. has infrasonic monitors for meteorite impact, but that's probably expensive equipment.

Right now, I'm dying with a cold, and I'm going to Montreal this weekend for water polo, and wine bottle filling. In the meantime, keep those cards and letters and clicks coming!

ps. I have now found with the hydro line, it is not wind related. But the line is 5 km long, and acts like a perfect sonic transmitter (like my slinky!). It even has high-frequency zinging noises (p-waves?). I love dynamics problems, reminds me of Darlington!

4 comments:

hypocentre said...

You can do infrasound monitoring with a microphone. Just because the ear can't hear it doesn't mean that a mic can't record it. For windfarms we actually use a microbarograph.

There are instructions to build a cheap one here [caveat - I've not tried this]

Harold Asmis said...

My suspicion is that none of this comes from a direct source, but due to a local resonance which can bump things up by a factor of 10. The other problem is figuring out human sensitivity.

hypocentre said...

For the windfarm study we superglued accelerometers on the wind turbine towers to match them to seismometers and microbarographs. We were also allowed to switch the windfarm turbines on and off to check the source of the noise.

Interestingly, seismic noise is high on high wind speed days, but infrasound is high on low wind speed days (better propagation in laminar rather than turbulent airflow).

Human sensitivity is another thing. This can be seriously affected by the building you are in and the window surface area.

Harold Asmis said...

I would think that a sealed house would act as a big amplifying balloon.