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.