Decibel
A logarithmic unit for ratios of power or amplitude. 0 dB is the threshold of human hearing.
Definition
The decibel (dB) is one-tenth of a bel. It is a logarithmic unit used to express the ratio of two values of a power or field quantity. For sound pressure level, 0 dB is defined as 20 μPa — the threshold of human hearing. Each 10 dB increase represents a 10× increase in acoustic power.
Formula
L = 20 × log₁₀(p / p₀) dB, where p₀ = 20 μPa
Examples
- Normal conversation: ~60 dB.
- Rock concert: ~110 dB.
- Pain threshold: ~130 dB.