The Problem of Noise Reduction with Reference ... - CAFE Foundation
The Problem of Noise Reduction with Reference ... - CAFE Foundation
The Problem of Noise Reduction with Reference ... - CAFE Foundation
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
(’) &16p=lo..,,watts per square centimeterand, if I is considered as a mean value, tinetotalenergy radiated per cecond is.+16E=4TTT2X1O L) watts (2)where L is the distance from tke source..<strong>The</strong> sound inten~ity level MY also be ex?ressed interms <strong>of</strong> tke root -me~-square pressure <strong>of</strong> the sound byuse <strong>of</strong> the following rormula:92P- X 10-7 watts ~er squzre‘mcentimeterwhere the root-meane squaz’ep mssure p is in dynes per -square centimeter, the dansity p is in &rms ‘per “cubiccentimeter, and the velacity <strong>of</strong> sound c is in centirlettir”sper second. Tjmder standard oondi tion~ t% energy level<strong>of</strong> 10-16 watts ger square centimeter corresponds to a ‘—pressure <strong>of</strong> 0.QO02 dyne per square centimeter. Thus thesound intensity level may be expressed as= 74 + 20 Ioglo p decibels (3) ..-. —A pressure <strong>of</strong> one d~e per square centime txjrc orresp endsto 74 decibels.—.-.<strong>The</strong> following table conveys a concept <strong>of</strong> the stepstn the s~~m.d scale by Introducing the effect <strong>of</strong> distancefrom a given source and by a ccnnpafison <strong>with</strong> commonlyrecognized sound levels:—3
Change language