# Noise & Vibration Conversions

**B** - An abbreviation of bel, the logarithm of the ratio of two powers. The decibel is one tenth of a bel.
**bel** - The bel is the logarithm of the ratio of two powers, and the decibel is one tenth of a bel.
**Decibel** - The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.
**Mel** - A proportional scale, in which equal intervals correspond to equal perceived interval sizes.
**Pascal** - The SI derived unit of pressure.
**Pressure** - Defined as the force exerted per unit area.
**Stiffness** - Stiffness is the ratio of change of force (or torque) to the corresponding change in translation (or rotational) deflection of an elastic element.