The decibel scale

In acoustics, the decibel (dB) scale is a scale for measuring the relative loudness of two sounds. For example, environmental noise is often measured as follows:

L = 20 log (p/p0)

where L is the sound pressure level (in dB), p is the sound pressure amplitude, and p0 is a reference amplitude of 20 micropascals (less than one billionth of atmospheric pressure). On this scale, a barely audible sound (p = p0) has a sound pressure level of 0 dB, normal conversation (p = 1,000*p0) is at a level of around 60 dB, and a jet engine at close range (p = 1,000,000*p0) is at a level of around 120 dB.

Similar decibel scales are used in other branches of science and engineering to measure electrical power levels and other signal levels, always with respect to some reference level.

In Sonar, decibels are used in several places:

To indicate volume levels of audio tracks in the Track view, Track Inspector and Console view

To indicate the effects of filters and equalizers

The reference level (0 dB) usually corresponds to the current loudness of the sound. A positive change in decibels makes the sound louder; a negative change makes the sound quieter.

 

See:

Digital audio fundamentals