text: The geomagnetic field strength and hence precession frequency varies with location and time.
  : Larmor precession frequency =  magnetogyric ratio x magnetic field
  : Proton magnetogyric ratio =  42.576 Hz/μT (also written 42.576 MHz/T or 0.042576 Hz/nT)
  : Earth's magnetic field:  30 μT near Equator to 60 μT near Poles, around 50 μT at mid-latitudes.
  Thus proton (hydrogen nucleus) EFNMR frequencies are audio frequencies of about 1.3 kHz near the Equator to 2.5 kHz near the Poles, around 2 kHz being typical of mid-latitudes. In terms of the electromagnetic spectrum EFNMR frequencies are in the VLF and ULF radio frequency bands, and the audio-magnetotelluric (AMT) frequencies of geophysics.
  Examples of molecules containing hydrogen nuclei useful in proton EFNMR are water, hydrocarbons such as natural gas and petroleum, and carbohydrates such as occur in plants and animals.