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Decibel

The decibel, abbreviated dB, is a unit used to express the base-10 logarithm of a ratio. A power ratio P/P_0 has level

L=10log_(10)(P/(P_0)) dB.

When power is proportional to the square of a field amplitude, the corresponding amplitude ratio is L=20log_(10)(A/A_0) dB. A decibel value is dimensionless, although a stated reference value P_0 or A_0 is needed when it is used to describe an absolute level rather than a ratio. In particular, a signal-to-noise ratio can be expressed in decibels.

See also

Amplitude, Logarithm, Signal-to-Noise Ratio

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References

National Institute of Standards and Technology. Guide for the Use of the International System of Units (SI). NIST Special Publication 811. Gaithersburg, MD: National Institute of Standards and Technology, 2008. https://doi.org/10.6028/NIST.SP.811e2008.

Cite this as:

Weisstein, Eric W. "Decibel." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Decibel.html

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