SCIENTIFIC RESEARCH APPLIED TO THE TELEPHONE 261 



about eight times the power of those from women. Also, as stated 

 above, for pitches above one — that is, for tones having vibration rates 

 above two thousand cycles per second— the voice power for women is 

 greater than for men. For the half-octave in the region of pitch three 

 octaves above one thousand cycles, it is about ten times greater. 



For some reason which is not very evident, women use higher pitch 

 sounds for producing the fricative consonants, and this results in the 

 greater power shown in the regions of higher pitch. Every one who 

 is familiar with such transmission systems knows well that these 

 high-frequency components are nearly always eliminated. While 



FREQUENCY IN CYCLES PER SECOND 

 62 125 250 500 1000 2000 4000 8000 16,000, 



-4 -3-2-1 I 2 3 4 



PITCH IN OCTAVES 



Fig. 4 — Distribution of speech power in fractions of the total power for half-octave 

 intervals above and below 1000 cycles. 



these sounds are not of controlling importance in properly under- 

 standing speech, it is evident that the women's voices are somewhat 

 handicapped as compared with men in systems which eliminate them. 



Hearing 



Paralleling our research on speech sounds, an investigation of hearing 

 has been under way in Bell Telephone Laboratories. Broadly speak- 

 ing, the aim has been to arrive at an accurate physical description 

 and a measure of the mechanical operation of human ears in such 

 terms that we may relate them directly to our electrical and acoustical 

 instruments. We have measured the keenness of the sound-discrimi- 

 nating sense, and determined what is the smallest distortion which 



