362 BELL SYSTEM TECHNICAL JOURNAL 



and also its distance from the mouth of the speaker, it is possible to 

 calculate approximately the average speech power. 



The other type of meter shown in Fig. 13 consists of a series of 

 parallel circuits, each containing an argon filled three-electrode tube 

 connected in such a way that in adjacent circuits the tube breaks 

 down and allows the passage of current for voltage levels which are 

 6 db (decibels) apart. Ten such circuits then cover a range of 54 db. 



Fig. 14 — Photograph of the level analyzer. 



In each of these circuits a relay and counter are connected so that for 

 each tube discharge the counter operates. In this way the number of 

 times the tube breaks down is automatically registered. The speech 

 wave coming from the rectifier is sent into this meter where the peak 

 values are measured; that is, the number of times the pressure exceeds 

 a value fixed by each of these circuits will be registered automatically 

 by the corresponding counter. The apparatus is arranged so that 

 every other 8th second interval is measured, the intervening interval 



