Thursday, November 13, 2008

Infrasonic Pollution - Part 2 - Measurement

I looked forever for cheap measurement systems, and finally did a search on 'usb accelerometer'. Boy are these neat! I found a stand-alone stick with a +-2g sensor, and its own memory, only for about 80 bucks. I'd get one, if I had any money. There are other tethered usb accelerometers, available for mostly for robots. In fact, the laptop seismometer project wants to move to usb accelerometers, because they can be attached to a structural element, and used with desktops.

For atmospheric infrasonics, I was looking at wide-band usb microphones, which are also reasonable.

Once you use these things, you should eventually get a power spectrum plot of the noise, something like this:

This is from Wikipedia Mains Hum. You will notice the big spread of harmonics. These are the muliples and whole fractions of 60 Hz. Notice the big spread into low frequencies.

For wind turbines, you will get a different spread. A base measurement is extremely important for mitigation, which we will discuss later, when I feel like it.

4 comments:

hypocentre said...

If you want some seismic & infrasound spectrograms from wind turbines you find some in this pdf file here.

Harold Asmis said...

Thanks, that must have been a fun project.

Mona Albano said...

It's probably streetcars. The newer, heavier streetcars produce subsonic rumbles. That's probably why people don't ride them if they don't have to, to say nothing of living along streetcar lines. And they were going to last practically forever. Unfortunately, they are 3 times heavier than the old streetcard so we have to rebuild the roadbed every five years. So what we save on streetcar maintenance we more than lose on road maintenance.

Harold Asmis said...

So, you need a seismometer, too!