Level (logarithmic quantity)

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In the International System of Quantities, a level is the logarithm of the ratio of a quantity Q to a reference value of that quantity, Q0.[1][2] Examples are sound pressure level, sound power level and sound exposure level.[3] In equation form: LQ = log(Q/Q0). The neper, bel and decibel (one tenth of a bel) are all units of level.


  1. ^ ISO 80000-1:2009
  2. ^ W M Carey, Sound Sources and Levels in the Ocean, IEEE J Oceanic Eng 31:61-75(2006)
  3. ^ ISO 80000-8:2007