The Sound of Lightning on the South Pole

This afternoon while driving home from work, NPR played an audio clip from Jim Hetrick of Stockton, CA of low frequency sound waves of lightning.  The lightning took place in the Northern hemisphere. By the time the waves made it to the South Pole, the sound had an interesting distortion because the lower frequency sound waves and higher frequency sound waves travel at different speeds.  It is an interesting sound - not something you would recognize if you heard it.