ROOM NOISES IN TELEPHONE LOCA TIONS 



663 



nents in the low- and middle-frequency ranges are in general not far 

 different. The above analysis is, of course, very rough, as the whole 

 range from 250 to 5600 cycles is divided into only three bands. 



Room Noise in Residence Locations. — Measurements were made in 96 

 residence locations. 



Figs. 6 and 7 show distribution curves for these measurements. 

 Compared with the corresponding measurements made in business 



100 



90 



5 80 



a. 



D 

 if) 



< 70 



O 



u 

 O 

 < 



I- 

 z 



LU 



o 

 a. 



60 



50 



40 



< 



D 

 D 



u 



30 



20 



10 



10 20 30 40 



WARBLER READINGS-THRESHOLD SHIFTS IN db 



Fig. 7 — Results of measurements of noise in residence locations by masking method. 



locations it is apparent that the room noises encountered in residences 

 were not only much smaller in magnitude but also varied less in magni- 

 tude than business room noises. The average of the residence room 

 noises is about 18 db less than the average of the business room noises, 

 while the spread in residence room noise (using the 95 per cent and 5 per 

 cent points on the curves as limits) is 20 db, compared to 40 db for busi- 

 ness noise; the standard deviation of the residence measurements is 6 

 db, compared to 12 db for the business neasurements. Unlike the 



