Decibels and Damage
Loudness is measured in decibels (dB). The absolute threshold for human hearing—the softest sound a human can hear—is described as 0 dB. Loud noises, such as the 140 dB produced by a jet engine, cause immediate nerve damage leading to hearing loss. Chronic exposure to moderately loud noise, such as traffic or an MP3 player near maximum volume, can also cause damage (Keith, Michaud, & Chiu, 2008).

Airplane, istockphoto/Thinkstock; Motorcycle: Vasiliy Vishnevskiy/Alamy; Whispering women, Photosindia/Getty Images