A sound’s amplitude, or strength, is measured in units called decibels (dB). Normal conversation has a sound level of approximately 60 decibels. Audiologists say that the longer you are exposed to anything louder than 85 decibels, the greater will be the eventual loss of hearing. The louder the sound, the faster the damage to hearing. A Newsweek magazine report noted: “Your ear can safely handle two hours with a power drill (100 dB), but not more than 30 minutes in a noisy video arcade (110 dB). Every 10-decibel increase on the sound scale represents 10 times more ear-battering noise.” Tests confirm that sound becomes painful at approximately 120 decibels. Incredibly, some home stereo equipment can produce sound at more than 140 decibels!​—See the accompanying box.

[Box on page 20]

Approximate Decibel Level of Some Common Sounds

• Breathing​—10 decibels

• Whispering​—20 decibels

• Conversation​—60 decibels

• Rush-hour traffic​—80 decibels

• Food blender​—90 decibels

• Passing train​—100 decibels

• Chain saw​—110 decibels

• Passing jet plane​—120 decibels

• Shotgun blast​—140 decibels