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The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 10 1/10 (approximately 1.26) or root-power ratio of 10 1/20 (approximately 1.12). [1] [2]
A gain greater than one (greater than zero dB), that is, amplification, is the defining property of an active component or circuit, while a passive circuit will have a gain of less than one. [ 4 ] The term gain alone is ambiguous, and can refer to the ratio of output to input voltage ( voltage gain ), current ( current gain ) or electric power ...
Sound exposure level (SEL) is a logarithmic measure of the sound exposure of a sound relative to a reference value. Sound exposure level, denoted L E and measured in dB, is defined by [1]
The noise figure is the difference in decibel (dB) between the noise output of the actual receiver to the noise output of an "ideal" receiver with the same overall gain and bandwidth when the receivers are connected to matched sources at the standard noise temperature T 0 (usually 290 K).
being approximately the lowest sound intensity hearable by an undamaged human ear under room conditions. The proper notations for sound intensity level using this reference are L I /(1 pW/m 2) or L I (re 1 pW/m 2), but the notations dB SIL, dB(SIL), dBSIL, or dB SIL are very common, even if they are not accepted by the SI. [6]
It is essential to know which category a measurement belongs to when using decibels (dB) for comparing the levels of such quantities. A change of one bel in the level corresponds to a 10× change in power, so when comparing power quantities x and y, the difference is defined to be 10×log 10 (y/x) decibel.
to calculate a current situation based on existing physics, mostly when a physical measurement at a location is impractical; to predict the resulting immission levels based on a planned change, e.g. set up of a new machine; Mostly, noise calculation is part of any such planning process and may become part of the decision process for physical change
The carrier-to-receiver noise density ratio is usually expressed in dB-Hz. The noise power density, N 0 = kT , is the receiver noise power per hertz , which can be written in terms of the Boltzmann constant k (in joules per kelvin ) and the noise temperature T (in kelvins).