Level
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Level
</dt>
In acoustics, the logarithm
of the ratio of that quantity to a reference quantity of the
same kind. The base of the logarithm, the reference quantity,
and the kind of level must be specified.
</dd>
Examples of kinds of levels in common use are electric
power level, sound-pressure-squared level, voltage-squared level.
Level as here defined is measured in units of the logarithm of
a reference ratio that is equal to the base of logarithms. In
symbols,
<math>L = logr (q/q0) </math>
</p>
where L is level of kind determined by the kind of quantity
under consideration, measured in units of log<math>r</math>;
r is the base of logarithms and the reference ratio; q is the
quantity under consideration; and <math>q0</math>
is the reference quantity of the same kind. Differences in the
levels of two like quantities q<math>1</math> and
q2 are described by the same formula because, by the
rules of logarithms, the reference quantity is automatically
divided out:
</p>
logr (q1 /q0) - logr
(q2 /q0) = logr (q1
/q2).
</p></dd>
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
