What does decibel mean?
A decibel is a logarithmic unit used to express the ratio between two values of a physical quantity — most familiarly the intensity of sound. Named in honour of Alexander Graham Bell, one decibel is one tenth of a bel, and because the scale is logarithmic, small numerical increases represent large jumps in actual energy: every rise of ten decibels corresponds to a tenfold increase in sound power. This makes the unit ideal for spanning the enormous range of human hearing, from a whisper at around 30 decibels to a rock concert or jet takeoff at well over 100. Beyond acoustics, decibels are used in electronics and telecommunications to describe signal strength and gain. The word appears frequently in discussions of hearing damage, noise regulations, and audio equipment, making it an essential term for understanding how we measure and talk about sound.
nounA unit used to express the ratio of two values of a physical quantity, most commonly sound intensity or loudness, on a logarithmic scale; one decibel equals one tenth of a bel.
- A logarithmic unit (one tenth of a bel) for expressing ratios of power or intensity, especially of sound, equal to ten times the common logarithm of the ratio.
"The noise of the jet engine measured over 120 decibels, well above the threshold of pain."
"Prolonged exposure to sounds above 85 decibels can cause permanent hearing damage."
"The amplifier boosted the signal by three decibels without introducing any distortion."
Regular plural; often used with figures as in '90 decibels'. The abbreviation dB serves for both singular and plural.
"The concert reached peaks of 110 decibels."
Every 10-decibel increase doesn't sound twice as loud to your ear — it represents ten times more sound energy, which is why 120 decibels is a million times more intense than a whisper.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of decibel
The word decibel combines the prefix 'deci-' from Latin 'decimus', meaning tenth, with 'bel', a unit named after Alexander Graham Bell, the inventor of the telephone. The bel was devised in the early twentieth century by engineers at Bell Telephone Laboratories to express ratios of power in telephone circuits; the decibel soon became the preferred practical size for the unit. It shares its Latin root with related terms such as decimal, decile, and decimate.
Related word forms
How decibel is actually used
Primarily a technical and scientific term, though it appears in everyday contexts concerning noise levels, hearing protection, and audio equipment. Decibel values are always relative measurements comparing one quantity to a reference value, not absolute units like meters or kilograms.
Easily confused with decibel
A bel is the larger parent unit named after Alexander Graham Bell, and a decibel is simply one tenth of a bel.