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:
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.
- Near total silence - 0 dB
- A whisper - 15 to 30 dB
- Refrigerator - 40 dB
- Normal conversation - 60 dB
- Dishwasher - 75 dB
- Heavy city traffic or school cafeteria 85 dB
- A lawnmower - 90 dB
- Snowmobile - 100 dB
- Personal stereo (ipod) at maximum level - 105 dB
- A car horn, rock concert, or orchestra - 110 dB
- A rock concert, jet engine or siren - 120 dB
- A gunshot, firecracker or jet taking off - 140 dB
- Firecracker or shot gun firing at close range - 140 to 165 dB
Hyperacusis patients often have difficulty with sounds exceeding 60-65 decibels. For this reason, it is often difficult for the hyperacusis patient to tolerate conversation with varying degrees of loudness. In addition to the decibel (loudness) level of sound, hyperacusis patients also have difficulty with sudden shifts in sound (their dynamic range). For more information on this, read the Supplement section of our website.
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).