Decibel

Decibel (dB) definition
Decibel (symbol: dB) is a logarithmic unit that indicates ratio or gain.

Decibel is used to indicate the level of sound waves and electronic signals.

A logarithmic scale can describe very large or very small numbers with shorter notation.

A dB level can be thought of as the relative gain of one level over another level or as an absolute level on a logarithmic scale for well-known reference levels.

Decibel is a dimensionless unit.

The ratio in waves is the base 10 logarithm of the ratio P 1 and P 0 :

Ratio B = log 10 ( P 1 / P 0 )

A decibel is a tenth of a bel, so 1 bel equals 10 decibels:

1B = 10 dB

Power ratio
The power ratio in decibels (dB) is 10 times the base 10 logarithm of the ratio of P 1 and P 0 :

Ratio dB = 10⋅log 10 ( P 1 / P 0 ).