# Ratio between two field quantities expressed in decibels

## Description

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.

## Variables

L_{AdB} | The ratio (in dB) of a field amplitude to another field amplitude (dimensionless) |

A_{1} | The measured amplitude (same units to Ao) (dimensionless) |

A_{0} | The reference amplitude (same units to A1) (dimensionless) |