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

• 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

The Noise app gently tells me that sound levels have exceeded 80 decibels. —Bill Schiffmiller, Forbes.com, 30 June 2025

Normal operation is speedy and not terribly loud (around 50 decibels), but there is a quiet mode that moves slowly and keeps the volume under 35 decibels. —Simon Hill, Wired News, 18 June 2025

In our lab test, the fan measured 50.1 decibel reading at its lowest speed, which provided a nice white noise. —Jessica Comstock, Better Homes & Gardens, 2 June 2025

There, his star pupil could train with the comparative reduction in decibels down to a 747 on takeoff. —Bill Dwyre, Los Angeles Times, 16 May 2025

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