Thunder- The sound waves produced by the explosive heating of the air in the lightning channel during a return stroke. It originates as shock waves close to the channel, and moves radially away from the channel. Thunder changes in pitch with varying distances from the channel. The closer one is to the lightning flash, the more high-pitched and 'crackle-sounding' the thunder. The further away, the more low-pitched and 'boom-rumble' sounding it is. Thunder rumbles and crackles because the lightning channel is crooked and jagged, causing the sound waves to arrive at the hearer at different times and directions. If lightning strikes closer than around 300 feet, the observer will hear one loud, startling, high-pitched bang which is not 'sound wave' thunder, but the shock wave, sometimes preceded by a faint crackling noise. (See Shock Wave) For more detailed information on thunder, visit the wvlightning.com Thunder Center.