ROOM NOISES IN TELEPHONE LOCA TIONS 653 



ment. Studies are being made of the effects of noise on living beings, 

 including effects on the efficiency of workers.- In all of this work, 

 quantitative measurement is important. 



For the specific problem in hand, it was desired to obtain informa- 

 tion on the magnitudes of room noises, as well as some general indica- 

 tion of the frequency composition of typical room noises. 



While it is recognized that ordinary room noise is a highly variable 

 quantity changing from instant to instant in intensity and frequency 

 composition, it is felt that sufficient measurements were made to specify 

 the makeup of a typical room noise for use in the laboratory tests, and 

 in addition to obtain an indication of the effect of various factors, de- 

 scribed below, upon the noise. Since it was desired to make the meas- 

 urements as representative as possible of typical telephoning conditions 

 they were made at times of day and in types of locations determined by 

 a study of telephone message traffic. Since the results would be af- 

 fected by the choice of locations, they are presumably less typical for 

 non-telephone than for telephone purposes. 



The residences included in the survey ranged from apartments in 

 large city buildings to small homes in outlying towns. In the business 

 locations were included offices, stores, factories and workshops, and 

 public buildings, such as hotels and clubs.^ Establishments of various 

 characters were included in each classification ; they ranged in size from 

 small stores to great manufacturing plants. 



In making all measurements, an attempt was made to simulate the 

 normal conditions which would obtain when a telephone call was 

 placed. If noises existed in the room, which would be discontinued 

 when the telephone was being used, such noises were stopped while the 

 measurements were being made. On the other hand, care was taken 

 to see that none of the normal noises of a particular location was dis- 

 continued because of the fact that measurements were being taken. 



It was recognized that there would be a difference between the room 

 noise experienced on local and on long-distance calls. The survey was 

 made on the basis of telephone traffic as a whole, which consists pre- 

 dominantly of local calls. 



The survey consisted of two series of tests, one made during the 

 months of January, February, March and April, and the other made 

 during the months of July and August. The former series was the 

 more comprehensive, including 205 measurements; the results given 

 herein are based on this series of tests except where specifically noted 



^ D. A. Laird, "The Effects of Xoise," Jl. Acoustical Soc. Amer., Jan. 1930, p. 256. 

 ' In public buildings, only a very small proportion of the telephone locations 

 tested were in booths or at coin-box telephones. 



