Queries, comments, suggestions? Please contact us.



Area Oscillations, signals and related devices / Transmission characteristics and performance; Distortion

IEV ref702-07-02

Symbol
dB

en
decibel
a unit used to express the ratio of two powers by ten times the decimal logarithm of this ratio

NOTE 1 – The decibel may also be used to express the ratio of two field quantities. To obtain the same numerical value as for the corresponding power ratio, the logarithm of the field quantity ratio is multiplied by the factor 20, assuming that the impedances are equal.

If P1 and P2 are two powers, their ratio expressed in decibels is:

10lg P 1 P 2 MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiaaigdacaaIWaGaaGPaVlaabYgacaqGNbWaaSaaaeaacaWGqbWaaSbaaSqaaiaaigdaaeqaaaGcbaGaamiuamaaBaaaleaacaaIYaaabeaaaaaaaa@3DB9@

The relation between a field quantity ratio and the corresponding power ratio is dependent on the impedances.

If P1 and P2 represent the powers dissipated by currents I1 and I2 in resistances R1 and R2, then:

10lg P 1 P 2 =10lg I 1 2 I 2 2 R 1 R 2 =20lg I 1 I 2 +10lg R 1 R 2 MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=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@5F0D@

NOTE 2 – Guidance for the use of the decibel and appropriate symbols to represent the ratios of various quantities is given in CCIR Recommendation 574, in CCITT Recommendation B.12, and in IEC publication 27-3.


fr
décibel, m
unité servant à exprimer le rapport de deux puissances par dix fois le logarithme décimal de ce rapport

NOTE 1 – Le décibel permet aussi d'exprimer le rapport de deux grandeurs de champ. Pour obtenir la même valeur numérique qu'avec le rapport des puissances correspondantes, le logarithme du rapport des grandeurs de champ est multiplié par le facteur 20, en supposant que les impédances soient égales.

Si P1 et P2 sont deux puissances, leur rapport exprimé en décibels est:

10lg P 1 P 2 MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiaaigdacaaIWaGaaGPaVlaabYgacaqGNbWaaSaaaeaacaWGqbWaaSbaaSqaaiaaigdaaeqaaaGcbaGaamiuamaaBaaaleaacaaIYaaabeaaaaaaaa@3DB9@

La relation entre un rapport de grandeurs de champ et le rapport des puissances correspondantes dépend des impédances.

Si P1 et P2 représentent les puissances dissipées par les courants I1 et I2 dans les résistances R1 et R2:

10lg P 1 P 2 =10lg I 1 2 I 2 2 R 1 R 2 =20lg I 1 I 2 +10lg R 1 R 2 MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=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@5F0D@

NOTE 2 – Des directives pour l'emploi du décibel et de certains symboles pour désigner les rapports de certaines quantités sont données dans la recommandation 574 du CCIR, dans la recommandation B.12 du CCITT, ainsi que dans la publication 27-3 de la CEI.


ar
ديسيبل (وحدة قياس فى مستوى الشدة بين صوتين متساويين التردد)

de
Dezibel, n
Einheitenzeichen: dB

es
decibelio

it
decibel

ko
데시벨

ja
デシベル

pl
decybel

pt
decibel

sv
decibel

Publication date: 1992-03
Copyright © IEC 2018. All Rights Reserved.