As a lightning bolt strikes, the air around it contracts and expands very rapidly due to the intense heating and cooling in the atmosphere around the bolt.  This rapid contraction and expansion creates the sound that we hear as thunder.  A clap of thunder typically registers 120 decibels (dBA).  That is ten times louder than a garbage truck, chain saw, or pneumatic drill.  Now for an even more interesting comparison.  Sitting in front of the speakers at a rock concert can expose you to a nearly continuous 120 dBA, which can seriously harm your hearing.  In other words, it's a good thing is doesn't thunder all the time!

What do thunder and a garbage truck have in common?  Not much...a clap of thunder is nearly ten times as loud as a garbage truck!