An example
of a sound spectrum
(lower right corner) that actually peaks
in the infrasound.
Up to this point we have explained
thunder as being due to the
explosive expansion of a hot lightning
channel. This may not be
the cause of all of the emissions at
infrasonic frequencies. Some
researchers have suggested that a sudden
change in the cloud
electrostatic field caused by a lightning
discharge might be the cause
of the very low frequency infrasonic
emissions.