A decibel is the unit used to measure the intensity of a sound. It is abbreviated as dB. On the decibel scale,the smallest sound that can be heard is O dB. This is close to total silence. A sound that is ten times the intensity of 0 dB is rated as 10 dB. A sound 100 times in intensity is 20dB. ,a sound 1000 times in intensity is 30 dB, and so on. Our normal conversation is 60 dB. When you mow the lawn the sound of the lawnmower is 90 dB. Have you ever attended a rock concert? The sound there can get as high as 120 dB. A firecracker set off on Independence Day comes in at 140 dB.