A Survey of Room Noise in Telephone Locations * 



By W. J. WILLIAMS and RALPH G. McCURDY 



This paper describes a survey made to determine the range of magnitudes 

 of room noise present in telephone locations. Measurements were made in a 

 total of 250 locations in New York City and environs, distributed among 

 businesses and residences in accordance with telephone traffic distribution. 

 In each location, measurements were made by a marginal audibility method 

 using the human ear as a part of the measuring device, and by a visual indi- 

 cating meter. A brief description is included of the apparatus employed 

 with each of these methods. Results are presented for measurements made 

 in various classes of rooms, under winter and summer conditions. 



AMONG the projects of the Joint Subcommittee on Development 

 and Research of the National Electric Light Association and Bell 

 System is one (No. 4) which is studying the effects of noise ^ on telephone 

 transmission and methods for its measurement. It was appreciated 

 that, in addition to noises of electrical origin caused by exposures to 

 power circuits or by sources incidental to the operation of the telephone 

 system, there are also noises in the rooms in which telephones are used 

 which have an important effect on telephone service. In studying the 

 effects of noises, it is, of course, necessary to consider both noises of 

 electrical origin and room noises. It was desired that, in laboratory 

 tests of the effects of line noises on speech transmission, typical amounts 

 of room noise should be provided at the test location. The survey de- 

 scribed hierein was made to obtain room noise data for these laboratory 

 tests. 



The methods described should be of general interest in connection 

 with other noise problems. Increasing attention is being given, both 

 in America and in Europe, to the general problem of noise as an unde- 

 sirable attribute of modern civilization. Some efforts are being made 

 to investigate sources of city noise. Modifications have been made in 

 the design of machines and appliances, such as typewriters, motor cars, 

 electric refrigerators, rotating electrical machinery, and domestic oil 

 burners, so as to reduce the noise involved in their operation. Atten- 

 tion is being given to the quieting of rooms by means of acoustic treat- 



*Presented at the Summer Convention of the A. I. E. E., Toronto, Ont., Canada, 

 June 23-27, 1930. 



'■ In this joint work, noise is taken to mean any extraneous sound which would 

 tend to interfere with telephone conversation. 



Room noise is used to include any extraneous sounds at the place where the 

 measurement is made, except those proceeding from the telephone receiver. It thus 

 includes, in addition to noises such as the rattling of papers or the roar of street 

 traffic, any other sounds extraneous to the telephone conversation, for example, 

 those of other conversations or of music produced nearby. 



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