Well which of the three do you want to pursue first?
(infrasound, magnetic fields, or 0-10 kHz RF where whistlers are found) Don't forget ambient electric field; that's interesting too!
There are some great DIY infrasound resources over at techlib.com.
The folks who do this professionally, like the test-ban treaty monitors, use fancy wind-noise reducers often consisting of large/complex PVC pipe structures, but apparently you can see lots of interesting activity in the near-infrasound, just below audible, without going to extreme lengths. The transducer of choice has traditionally been a capacitance manometer (google MKS baratron). I think eventually this paradigm may change as MEMS devices continue to improve. Obnoxiously, mfgs don't provide a noise level in rms Pa/sqrt(Hz), but reading between the lines, I think we are somewhere below 1 Pa/sqrt(Hz) for a single sensor. You could set up an array of 100s of these covering a square km or so, and by combining the signals get the wind filtering without the bother of a mechanical filter, and maybe ok noise performance.
Just as it is with RF, the higher up one lives (on a hill) the more and farther away are the sounds you hear.
This is probably because in a normal thermally stratified atmosphere (not a temperature inversion), sound waves bend upward. During an inversion, such as often forms in the predawn hours, it is sometimes possible to hear sounds from much further away. One of my project ideas, regrettably still in the daydream phase, is to "transmit" bandlimited pseudonoise through a loudspeaker and see how far away it can be detected with a small microphone array and synchronized correlator. There is enough ambient noise basically anywhere to dither the received signals, so ADC resolution and microphone self-noise are not hard limits; you can just correlate longer. Atmospheric stability (coherence time) must be the limiting factor, but I do not know what are typical values. In favorable conditions I can hear train horns from miles away, so similar range ought to be possible.