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Area Acoustics and electroacoustics / Levels

IEV ref801-22-13

en
spectrum density level
spectrum level
level of the limit, as the width of the band approaches zero, of the ratio of a specified quantity distributed within a frequency band to the width of the band

Note 1 – The kind of quantity must be specified, such as by (squared) sound pressure spectrum level.

Note 2 – In view of the fact that filters have finite bandwidths, practically the sound pressure spectrum level Lps is obtained for the centre frequency of the band by the formula:

L ps =10 log 10 ( p 2 /B ) ( p 0 2 / B 0 ) dB MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiaadYeadaWgaaWcbaGaaeiCaiaabohaaeqaaOGaeyypa0JaaGymaiaaicdacaaMc8UaaGPaVlaabYgacaqGVbGaae4zamaaBaaaleaacaaIXaGaaGimaaqabaGcdaWcaaqaamaabmaabaWaaSGbaeaacaWGWbWaaWbaaSqabeaacaaIYaaaaaGcbaGaamOqaaaaaiaawIcacaGLPaaaaeaadaqadaqaamaalyaabaGaamiCamaaDaaaleaacaaIWaaabaGaaGOmaaaaaOqaaiaadkeadaWgaaWcbaGaaGimaaqabaaaaaGccaGLOaGaayzkaaaaaiaaysW7caqGKbGaaeOqaaaa@4FD3@

where p and p0 are respectively the given field quantity and the reference quantity; B et B0 are respectively the effective bandwidth of the filter and the reference bandwidth of 1 Hz.

When Lp is the band pressure level observed through the filter, the above relation reduces to

L ps = L p log 10 ( B/ B 0 )dB MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaceaaK=GaamitamaaBaaaleaacaqGWbGaae4CaaqabaGccqGH9aqpcaWGmbWaaSbaaSqaaiaabchaaeqaaOGaeyOeI0IaaeiBaiaab+gacaqGNbWaaSbaaSqaaiaaigdacaaIWaaabeaakmaabmaabaWaaSGbaeaacaWGcbaabaGaamOqamaaBaaaleaacaaIWaaabeaaaaaakiaawIcacaGLPaaacaaMc8UaaGjbVlaabsgacaqGcbaaaa@4A77@


fr
niveau de densité spectrale, m
niveau de la limite du rapport d'une grandeur spécifiée répartie dans une bande de fréquences à la largeur de cette bande, quand la largeur de la bande tend vers zéro

Note 1 – La grandeur considérée doit êtrе précisée; exemple: niveau de densité spectrale du carré de la pression acoustique.

Note 2 – Puisque les filtres utilisés ont des largeurs de bande finies, le niveau de densité spectrale Lps du carré de la pression acoustique est pratiquement obtenues pour la fréquence médiane de cette bande par la formule:

L ps =10 log 10 ( p 2 /B ) ( p 0 2 / B 0 ) dB MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaaiaadYeadaWgaaWcbaGaaeiCaiaabohaaeqaaOGaeyypa0JaaGymaiaaicdacaaMc8UaaGPaVlaabYgacaqGVbGaae4zamaaBaaaleaacaaIXaGaaGimaaqabaGcdaWcaaqaamaabmaabaWaaSGbaeaacaWGWbWaaWbaaSqabeaacaaIYaaaaaGcbaGaamOqaaaaaiaawIcacaGLPaaaaeaadaqadaqaamaalyaabaGaamiCamaaDaaaleaacaaIWaaabaGaaGOmaaaaaOqaaiaadkeadaWgaaWcbaGaaGimaaqabaaaaaGccaGLOaGaayzkaaaaaiaaysW7caqGKbGaaeOqaaaa@4FD3@

p et p0 étant respectivement la valeur de la grandeur de champ considérée et la valeur de référence de cette grandeur; B et B0 étant respectivement la largeur de bande effective du filtre et la bande de référence de 1 Hz.

Lorsque Lp est le niveau de pression acoustique mesuré dans la bande correspondant au filtre, la relation ci-dessus se réduit à

L ps = L p log 10 ( B/ B 0 )dB MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbbjxAHXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeqabiGaciGacaqadmaadaqaaqaaaOqaceaaK=GaamitamaaBaaaleaacaqGWbGaae4CaaqabaGccqGH9aqpcaWGmbWaaSbaaSqaaiaabchaaeqaaOGaeyOeI0IaaeiBaiaab+gacaqGNbWaaSbaaSqaaiaaigdacaaIWaaabeaakmaabmaabaWaaSGbaeaacaWGcbaabaGaamOqamaaBaaaleaacaaIWaaabeaaaaaakiaawIcacaGLPaaacaaMc8UaaGjbVlaabsgacaqGcbaaaa@4A77@


ar
مستوى كثافة طيف

de
Spektraldichtepegel, m

es
nivel de densidad espectral

fi
spektritiheystaso

it
livello di densità spettrale

ko
스펙트럼 밀도 수준

ja
スペクトルレベル
スペクトル密度レベル

pl
poziom gęstości widmowej

pt
nível de densidade espectral

sv
spektral nivå

Publication date: 1994-07
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