MEASUEEMENT OF NOISE KAYE 



191 



Figure 11 (due to Norris) shows the progressive increase in the 

 noise level in a room when a window opening on to external noise 

 was gradually opened. It will be noted that a small opening may 

 produce a large effect. 



X8 

 i 

 t: 6 



yvo/se levs/ 

 With ^nry/nf W/h^ow Openihq 



Decibels /Voise let'e/ 

 Fig ORE 11 



Finally, considerable advantage may accrue in preventing noisv^f 

 which has gained entrance into a room from building up into a high 



60 



-2 60 



« 



•B. 

 w 



-^ 



z. 

 15 



o 20 



128 256 532 IQ24 2Q43 4Q96 8192 



Fre£j,uencij (cijcles per secj 



Figure 12. — Room noises 



level of reverberant sound, by lining the walls and ceilings with 

 absorbent materials. Certain banks and business houses in the city 

 (London) already employ the plan with advantage. I understand 



