192 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 2 



that many houses in New York line the roofs of their entrance 

 porches with acoustic absorbent, deriving, it is stated, beneficial 

 effects. 



Figure 12 (due to Gait) illustrates the effect on masking measure- 

 ments (made by a 6-band audiometer), in a room subjected to traffic 

 noise, of lining the walls with absorbent. As will be seen, the mask- 

 ing value was reduced by about 7 decibels on the average, corre- 

 sponding to a reduction in the reverberation period of from 5 seconds 

 to 1 second. 



