decibel

noun

deci·​bel ˈde-sə-ˌbel  -bəl 

1

a

: a unit for expressing the ratio of two amounts of electric or acoustic signal power equal to 10 times the common logarithm of this ratio

b

: a unit for expressing the ratio of the magnitudes of two electric voltages or currents or analogous acoustic quantities equal to 20 times the common logarithm of the voltage or current ratio

2

: a unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for the average pain level

3

: degree of loudness

also : extremely loud sound

—usually used in plural

Did you know?

The unit for measuring the relative intensities of sound is called a decibel. Because the decibel scale is logarithmic, a sound with an intensity that is twice that of a reference sound corresponds to an increase of little more than 3 decibels. In common practice, the reference point of 0 decibel is set at the intensity of the least perceptible sound, the threshold of hearing. On such a scale a 10-decibel sound is 10 times the intensity of the reference sound; a 20-decibel sound is 100 times the reference intensity, and so on. Normal conversation is usually around 60 decibels, an electric saw around 100 decibels, and amplified rock music around 120 decibels.

Synonyms of decibel

• noise
• roar

Examples of decibel in a Sentence

a rock concert blasting music at 110 decibels

the crowd decibels increased dramatically as the horses neared the finish line

Recent Examples on the Web

Colby Leider, a sound engineer, said early-evening readings near the festival hovered between 80 and 85 decibels. —Abby Dodge, CBS News, 28 Mar. 2026

In downtown Caldwell, the trains announce themselves with a shattering 100-decibel wave of sound. —Noah Daly, Idaho Statesman, 27 Mar. 2026

The loudest sound ever produced is said to be the 1883 eruption of the volcanic island of Krakatoa, which was estimated to be 310 decibels, which ruptured eardrums 40 miles away and could be heard as far as 3,000 miles away. —Kirk Kenney, San Diego Union-Tribune, 27 Mar. 2026

The two-stroke engine pumps about 90-110 decibels, 30 decibels above safe levels. —Chris Hildreth, The Orlando Sentinel, 26 Mar. 2026

Word History

Etymology

International Scientific Vocabulary deci- + bel

First Known Use

1928, in the meaning defined at sense 1a

Rhymes for decibel

• bagatelle
• caravel
• carousel
• carrousel
• citadel
• clientele
• commonweal
• demoiselle
• fontanelle
• infidel
• isabel
• machiavel

Kids Definition

decibel

noun

deci·​bel ˈdes-ə-ˌbel 

-bəl

: a unit for measuring the relative loudness of sounds

—abbreviation dB

Medical Definition

decibel

noun

deci·​bel ˈdes-ə-bəl  -ˌbel 

1

a

: a unit for expressing the ratio of two amounts of electric or acoustic signal power equal to 10 times the common logarithm of this ratio

b

: a unit for expressing the ratio of the magnitudes of two electric voltages or currents or analogous acoustic quantities equal to 20 times the common logarithm of the voltage or current ratio

2

: a unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for the average pain level