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BELL SYSTEM TECHNICAL JOURNAL 



time. It introduces loss in the absence of speech but reduces this loss 

 in proportion to the amplitude and duration of waves impressed upon 

 it. The time required for the loss change is such that abruptness of 

 noise change is absent and very short impulses of static do not effec- 



uj -20 



-28 



-36 



-28 -24 -20 -16 -12 -8 -4 4 8 12 16 



lOOO-CYCLE INPUT IN DECIBELS (RELATIVE TO I MILLIWATT) 



Fig. 1 — Input-output comparison of noise reducer and voice-operated relay. 



tively control the loss. This contrasts with a very fast limiter acting on 

 high-peak crashes only. 



The noise may control the loss if its average amplitude is strong 

 enough. Therefore, the control is made adjustable so that the noise 



