ROOM NOISES IN TELEPHONE LOCA TIONS 



661 



eluded in each sub-classification, and that consequently it is not safe to 

 generalize from these sub-groupings as to room noise conditions in gen- 

 eral. 



Averages of the room noise measurements for the different types of 

 business locations are shown in the following tableJ 



The above figures show a significant difference between the noise 

 measured in factories and that measured in other types of location. 

 The other differences shown were found not to be significant when ex- 

 amined in the light of the spread in values for individual locations in 

 each class. 



Averages of the business room noise measurements obtained in var- 

 ious sizes of towns are shown in the table below. 



These figures indicate that (with the exception of Class C towns) the 

 business noise measured in large cities was greater than that in smaller 

 towns. This is believed to hold true despite a fairly large spread in in- 

 dividual measurements within a given class. The exception in the 

 case of Class C towns is explained by the fact that a fairly large percent- 

 age of the measurements in this class were made in large factories. 



Room noise in business locations was observed to be quite complex in 



^ It will be noted that in the results given, the difference between the masking of 

 the middle-frequency tone and the meter reading is relatively constant. It was found 

 that for any considerable sub-group of the measurements, this difference was not far 

 from 15 db. This figure, of course, would not in general hold for a single noise selected 

 at random. There was a general tendency for the difference to be somewhat larger 

 for larger values of noise. 



