decibel

American  

[des-uh-bel, -buhl] / ˈdɛs əˌbɛl, -bəl /

noun

Physics.

1. a unit used to express the intensity of a sound wave, equal to 20 times the common logarithm of the ratio of the pressure produced by the sound wave to a reference pressure, usually 0.0002 microbar.

2. a unit of power ratio, the number of units being equal to a constant times the logarithm to the base 10 of the intensities of two sources.

3. a unit used to compare two voltages or currents, equal to 20 times the common logarithm of the ratio of the voltages or currents measured across equal resistances. dB, db

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decibel British  

/ ˈdɛsɪˌbɛl /

noun

1. a unit for comparing two currents, voltages, or power levels, equal to one tenth of a bel

2. a similar unit for measuring the intensity of a sound. It is equal to ten times the logarithm to the base ten of the ratio of the intensity of the sound to be measured to the intensity of some reference sound, usually the lowest audible note of the same frequency

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decibel Scientific  

/ dĕs′ə-bəl /

1. A unit used to measure the power of a signal, such as an electrical signal or sound, relative to some reference level. An increase of ten decibels in the power of a signal is equivalent to increasing its power by a factor of ten. As a measure of sound intensity, a zero-decibel reference is stipulated to be the lowest level audible to the human ear; the speaking voice of most people ranges from 45 to 75 decibels.

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decibel Cultural  

1. A unit of measurement of the volume of sounds.

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Etymology

Origin of decibel

First recorded in 1925–30; deci- + bel ¹

Explanation

A decibel is a unit of measurement that tells you exactly how loud a sound is. While a whisper is about 15 decibels, your neighbor's chain saw is about 120 decibels. Better invest in some ear plugs! Because our ears are so incredibly sensitive to noise, the decibel scale has an enormous range. The 120 decibel sound of an airplane's jet engine is actually one trillion times louder than the very quietest sound your ear can hear. The word decibel, coined in 1928 by engineers in the telephone industry, originally measured the efficiency of a telephone circuit.

Example Sentences

The numbers that were perhaps most telling though were on the Twickenham decibel meter, showing the love for a team that has not always felt it.

From BBC • Nov. 15, 2025

It's also hard to imagine anyone wanting to endure two hours of Will Ferrell yelling in “Bewitched” if Kidman weren’t onscreen to bring the decibel level down with her uniquely peculiar charms.

From Salon • Mar. 27, 2025

With the Bruins in the midst of another big run, Izzo’s only move was to call timeout as Mara flapped his arms to get fans to increase the decibel level.

From Los Angeles Times • Feb. 5, 2025

The decibel level rose from mere ear-splitting to near ear-drum-busting.

From BBC • Jun. 19, 2024

The science enthusiasts quickly gathered round, trying to get a peek at the heavy-looking metal box he was holding—his notorious decibel counter.

From "Anthem of a Reluctant Prophet" by Joanne Proulx