The decibel (abbreviated dB) is the unit used to measure the intensity of a sound. The decibel scale is a little odd because the human ear is incredibly sensitive. Your ears can hear everything from your fingertip brushing lightly over your skin to a loud jet engine.
In terms of power, the sound of the jet engine is about
1,000,000,000,000 times more powerful than the smallest audible sound.
That’s a big difference!
On the decibel scale,
the smallest audible sound (near total silence) is 0 dB. A sound 10
times more powerful is 10 dB. A sound 100 times more powerful than near
total silence is 20 dB. A sound 1,000 times more powerful than near
total silence is 30 dB. Here are some common sounds and their decibel
ratings:
- Near total silence – 0 dB
- A whisper – 15 dB
- Normal conversation – 60 dB
- A lawnmower – 90 dB
- A car horn – 110 dB
- A rock concert or a jet engine – 120 dB
- A gunshot or firecracker – 140 dB
You
know from your own experience that distance affects the intensity of
sound — if you are far away, the power is greatly diminished. All of
the ratings above are taken while standing near the sound.
Any sound above 85 dB can cause hearing loss,
and the loss is related both to the power of the sound as well as the
length of exposure. You know that you are listening to an 85-dB sound if
you have to raise your voice to be heard by somebody else. Eight hours
of 90-dB sound can cause damage to your ears; any exposure to 140-dB
sound causes immediate damage (and causes actual pain).