Ratio between two field quantities expressed in decibels


he decibel is a logarithmic unit used to express the ratio between two values of a physical quantity. The bel represents a ratio between two power quantities of 10:1, and a ratio between two field quantities of √10:1.
When referring to measurements of field amplitude, it is the ratio of the squares of measured amplitude and reference amplitude. A field quantity is a quantity such as voltage, current, pressure, electric field strength, velocity, or charge density, the square of which in linear systems is proportional to power.

Related formulas


LAdBThe ratio (in dB) of a field amplitude to another field amplitude (dimensionless)
A1The measured amplitude (same units to Ao) (dimensionless)
A0The reference amplitude (same units to A1) (dimensionless)