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.