The decibel (dB) is used to measure sound level. It is a logarithmic unit of measurement that expresses the intensity of sound relative to a specified or implied reference level.

The decibel is also used for a wide variety of other measurements in science and engineering. It is a logarithmic unit used to describe a ratio. It confers a number of advantages, such as the ability to conveniently represent very large or small numbers, a logarithmic scaling that roughly corresponds to the human perception of sound and light, and the ability to carry out multiplication of ratios by simple addition and subtraction.

## Units and Measures

The decibel is a dimensionless unit as it expresses a ratio of two quantities with the same unit. For example, two loudspeakers with different power, the first playing a sound with power P1, and another playing a louder version of the same sound with power P2. If everything else kept the same, the difference in decibels between the two speakers will be: 10 log (P2/P1) dB (where the log is to base 10)