A common measure of sound intensity ratio that is one tenth of a bel on the logarithmic intensity scale. It is defined as dB = 10 log₁₀(P₁ / P₂), where P₁ and P₂ are the relative powers of the sound.
The word decibel combines the prefix deci-, meaning one-tenth, with bel, a unit named after Alexander Graham Bell. It was created to describe a specific level of sound intensity.