292 



ARCHITECTURAL ACOUSTICS 



Fig. 12.8. The reference level is 10~^^ watts per square centimeter. It 

 will be seen that there is a wide variation in the noise from one location to 

 another. For example, 5 per cent of the residences have a noise level of 

 32 db while another 5 per cent have a noise level of 50 db. The factory 

 noise levels were taken in two parts of the country. The higher level is 

 for the Eastern part of the United States while the lower level is for the 

 Midwest. This is probably due to the different types of manufacturing. 



98 



rf)95 



3 80 



O 70 

 ^ 60 



UJ 

 O 50 



£40 



a 



I- 20 



< 

 _l 



Z) 



2 10 

 O 



5 



30 



50 60 70 80 



SOUND LEVEL IN DECIBELS 



Fig. 12.8. Room noise in residence, business, and factory locations. (After Seacord.) 



The noise level in various locations is shown in Table 12.2. All data 

 were obtained with a noise meter employing the characteristics of Fig. 11.18. 



G. Public Address Systems ^^. — The term public address system ordi- 

 narily refers to a sound reproducing apparatus for use in addressing large 

 assemblages. There are innumerable specific applications of sound re- 

 producing apparatus for this purpose. The problems in all these situations 

 are practically the same. It is the purpose of this section to consider some 

 typical examples of the use of public address systems. 



Regardless of the size of the athletic field or baseball park, a public ad- 

 dress system is useful for informing those in the stands of what is hap- 

 pening on the field. In general, the chief requirements are as follows: 

 uniform distribution of sound intensity in all parts of the stand, adequate 



"Olson, H. F., RCA Review, Vol. 1, No. 1, p. 49, 1936. 



