MEASUEEMENT OF NOISE — KAYE 165 



be out of the question, is emphatically a question of degree. Only 

 if a noise is exceptional and unreasonable, is there any likelihood of 

 restraining it by injunction. (Encycl. Brit.) 



So much for the legal aspect. It does, however, appear to point to 

 an acceptable popular definition of noise — " an acoustic redund- 

 ance " — or perhaps " an acoustic annoyance," and here we are re- 

 minded that the adjective " noisome " is literally " annoy-some." 

 (One recalls, too, that children have long been concerned with the 

 annoj'ance factor of noise as experienced by an oyster ! ) 



In other words, a noise is an acoustic disturbance which is unwel- 

 come, whether because of its excessive loudness ; its composition ; its 

 persistency or frequency of occurrence (or alternatively, its inter- 

 mittency) ; its unexpectedness, untimeliness, or unf amiliarity ; its 

 redundancy, inappropriateness, or unreasonableness; its suggestion 

 of intimidation, arrogance, malice, or thoughtlessness (it is well 

 known what depth of feeling can be stimulated in a pedestrian by 

 a motor horn) ; . . . and so on. 



We are clearly dealing with a subjective definition which takes 

 account of both the physiology and psychology of the individual, and 

 we ought not, therefore, to be surprised to find that " One man's 

 noise is another man's music." Incidentally the well-known fact that 

 listening to music engenders in some people an unquenchable desire 

 to converse, is doubtless associated with the rough-and-ready test 

 which we instinctively apply to a noise, that is, whether or not we 

 can hear one another speak. Conversation automatically languishes 

 in a tube train or airplane cabin, for example. 



We are fortified in our outlook on noise by the recent proposal of 

 the Acoustical Society of America to define a noise as " any unwanted 

 sound." Such a definition would seem to be adequate for those few 

 occasions when it is necessary or desirable to draw a distinction be- 

 tween noise and any other kind of sound. It also conforms to the 

 views of the telephone engineer who regards noise as any extraneous 

 sound which tends to interfere with the reception of desired sounds. 



THE FREQUENCY AND INTENSITY RANGES OF THE EAR 



As is the case in many branches of science, the physics of acoustical 

 research owes its present facility and exactitude largely to the de- 

 velopment of electrical methods of measurement. The key lay in the 

 invention of the electronic valve, and to this the subject owes an 

 impetus which it had long needed. 



Before we pass on to the question of noise measurement we shall be 

 well advised to review the relevant physical facts about the ear, 

 which is, of course, the ultimate critic in matters of noise. The foun- 

 dations of the subject rest largely on experiments with pure notes. 



