THE COMPANDOR 



319 



^MAX 



-20 



Z-30 



-60- 



-50 -40 -30 -20 



INPUT INTENSITY IN DECIBELS 



Fig. 2 — Range contro!. 



Intensity Range at Constant Volume 



However, even with speech adjusted to constant volume at the 

 transmitting point there are large variations in signal intensity from 

 syllable to syllable and within each syllable. For example, the energy 

 of some consonants as compared with the stronger vowels is down about 

 30 db. The importance of the weaker sounds is brought out by the 

 fact that in the case of commercial telephone sets a steady noise 30 db 

 below the energy in the strongest parts of the speech syllables pro- 

 duces an appreciable impairment in transmission efficiency. It is 

 accordingly desirable to maintain transmission conditions such that 

 generally more than this range is kept free from the masking effect of 

 noise. This range of intensities within the syllable is also of importance 

 in the operation of the voice-controlled switches used in the radio 

 system. The sensitivity spread between a voice operated relay which 



