# What Is A Decibel?

What is a decibel? How many decibels is a normal conversation? Will 29dB of noise reduction block out all the noise I can hear? In this article, we answer these questions and more.

A decibel is one unit on the decibel scale, which is a logarithmic scale. The name means one-tenth of a bel, a bel being an eponymous unit named for Alexander Graham Bell and used to compare power in electrical communication, voltage, or intensity of sound. The abbreviation of bel is B and decibel, dB.

The primary use of the decibel scale today is to test audibility, and the results are called the sound-pressure level (SPL), which is similar to loudness. The Occupational Safety and Health Association (OSHA) has set guidelines to help people determine the maximum loudness they should be exposed to. The SPL level that OSHA recommends is 85 decibels, above which special ear protection is required.

The human ear is extremely sensative to sound. Your ears can hear everything from a flick of a fingernail to a loud jet engine. In terms of power, a jet engine is 1 trillion times more powerful.

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
• Hotel lobby conversation 40-45 dB
• Normal conversation – 60 dB
• A lawnmower – 90 dB
• Thunder – 100 dB
• A car horn – 110 dB
• A rock concert or a jet engine – 120 dB
• A gunshot or firecracker – 140 dB

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).