Decibel

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Wiki: Decibel

"The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power) relative to a specified or implied reference level."

"An increase of 3 dB corresponds to an approximate doubling of power."

"The definitions of the decibel and bel use base-10 logarithms."

Prefix is "dB"

http://upload.wikimedia.org/math/a/2/e/a2e793ee0ab4494f07d205eaf4b08fa6.png or   http://upload.wikimedia.org/math/d/d/a/dda4f83175a03d80ba7bb86e93c9ebf4.png where X is the actual value of the quantity being measured, X0 is a specified or implied reference level, and then XdB is the quantity expressed in units of decibels, relative to X0

An increase/decrease of 1 dB corresponds to an approximate quarter power gain/loss. (ie 1=>1.25) An increase/decrease of 2 dB corresponds to an approximate half power gain/loss. (ie 1=>1.50) An increase/decrease of 3 dB corresponds to an approximate doubling of power gain/loss. (ie 1=>2) An increase/decrease of 6 dB corresponds to an approximate quadrupling of power gain/loss. (ie 1=>4) An increase/decrease of 9 dB corresponds to an approximate eight times the power gain/loss. (ie 1=>8) An increase/decrease of 10 dB corresponds to an approximate ten times the power gain/loss. (ie 1=>10) An increase/decrease of 20 dB corresponds to an approximate one hundred times the power gain/loss. (ie 1=>100)

So a change of 10 dB would be a change of 10 times the power. For example: To convert 1 kW (one kilowatt, or 1000 W) to decibels, use the formula (with base measure being 1 W):

http://upload.wikimedia.org/math/6/3/b/63b7de94ad592406b9b1edcc315ea48b.png