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# Decibel

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 Sub Topics Decibel is a measure of sound levels. It is difficult to do anything in audio and not encounter the decibel. The decibel offers a precise calculation that quantifies properties of an audio signal in a very useful form. The decibel offers a perceptually meaningful description of amplitude, one that the ears and brain can make sense of. The decibel appears in some form on almost every faceplate and user interface of every signal processor in the recording studio. Understanding the meaning of quantities in decibels is essential to understanding sound effects.

## Decibel Definition

Decibel is a measure to quantify the sound level. It is given by the logarithmic ratio of power, intensity or sound pressure etc. Basically it is a logarithmic ratio of physical quantity.

## Decibel Formula

The power equation that absolutely defines the decibel (dB) :
dB = 10log$\frac{P_{1}}{P_{2}}$

So, the decibel is ten times the logarithm of the ratio of two powers.

## Decibel Levels

The different decibel levels are listed below :

 Sound Source Decibel Level (dB) Jet takeoff 120 Construction site 110 Shout 100 Heavy truck 90 Urban street 80 Automobile interior 70 Normal conversation 60 Office 50 Broadcast studio 20 Rustling leaves 10

## Decibel Conversion

In general decibel is considered as the logarithmic ratio of powers. This power ratio can be converted in terms of voltage and current.

We know that,
dB = 10log$\frac{P_{1}}{P_{2}}$

Power is proportional to square of the voltage and current.
P = $I^{2}$R
P = $\frac{V^{2}}{R}$

So, the equation for dB in terms of voltage and current is,
dB = 20log$\frac{V_{1}}{V_{2}}$

dB = 20log$\frac{I_{1}}{I_{2}}$