4° 



SECTIONAL ADDRESSES 



varied origin. The positions which some of these noises occupy in a 

 scale of phons are shown in Fig. i, the upper half of which includes 

 various noises whose abatement would be acceptable in many circum- 

 stances. This is illustrated by the homely test which most of us apply 

 as a test of background of noise, i.e. the ease with which conversation is 



Approximate Loudness Levels of common noises. 



B.S. Loudness scale of phons. 



Phons 



ralEffilci 



Praximiti/ of aeroplane engine 



Proximity of riveting 

 or loud pneumatie drill 



Proximitu of loud, motor horn 



Noisy lorrt^ (50 m p.h.) at ZOfl 



Quttt ear {50 mp.h.)a.t ZO ft 



Loud conversation 



Quiet conversation 



Quiet electric motor at 3 ft 



Tearing of paper at 5ft 



Tickmq of watch at 3ft 



1000. eijcles per sec ; 



zero 0002 dyne 



per stf. cm. 



5701 



■60- 



■50- 



•40- 



•30- 



•20- 



■10- 



FiG, 



Near tfjreshold of pain 



In printing press room 



In busg machine shop, pump house etc. 



In tube train ; ioi,ndow open 



In busi^ tipping room 



In express train ; ujind-otu open 



In busg main street 



In guiet saloon car (SOm.p.h.) 

 In suburban train ; wlndotu open 

 In guiet residential street 



In verg guiet room 



In exlremelu guiet room 



Near threshold of hearing 



possible. At 60 phons, conversation is ' comfortable ' ; at 90 phons, 

 difficult ; and at no phons, virtually impossible. 



Among the noise problems on which the Laboratory has been con- 

 sulted in recent years, are the mitigation of the noises associated with 

 aeroplane-cabins and engine-testing factories, trains, ships, tube-railways, 

 buses, motor horns, pneumatic drills, printing works, transformer sub- 

 stations, cathedrals, assembly halls, business offices, flats, miniature rifle 

 ranges, building operations, and so on. Assistance is also being given in 

 connection with the Home Office experiments on air-raid warnings. 



