Decibel

What is a decibel, and how is it measured?

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). See this page for an exposure "ruler."

How Loud Is Too Loud? Bookmark

Protect Your Ears

Know which noises can cause damage. Wear ear plugs when you are involved in a loud activity.

• 110 Decibels

Regular exposure of more than 1 minute risks permanent hearing loss.

• 100 Decibels

No more than 15 minutes of unprotected exposure recommended.

• 85 Decibels

Prolonged exposure to any noise at or above 85 decibels can cause gradual hearing loss.

Decibels	Sound Source
150	Firecracker
120	Ambulance siren
110	Chain saw, Rock concert
105	Personal stereo system at maximum level
100	Wood shop, Snowmobile
95	Motorcycle
90	Power mower
85	Heavy city traffic
60	Normal conversation
40	Refrigerator humming
30	Whispered voice
0	Threshold of normal hearing