MEASUREMENT OF NOISE KAYE 



179 



diaphragm buzzer. An attenuator regulates the current through 

 the telephone receiver, which is applied to one ear, while the other 

 ear listens to the external noise. The instrument, which as supplied 

 is graduated in phons,^ can, with a little modification, be calibrated 



BarUhausen Audiomefer. 

 Aural inaPcljincj or tnaskinq o^ a bu33cr nol"e 



Electric Bujjcr 

 (800 cijclcs per sec) 



ACI'cnual'or 



Ear 'phone 



<!-" 



Noise Vo he 



measured 



flier 



Wesl'ern Elccl'ric Audiomel'er. 

 Aural mafchmq or masking o^ a valve -oscillator iioi's. 



Ear'pUonc wiHi 

 oj^-aefctip 



Valve -oscillol'or 

 (.64 1-0 8192 

 cijctes per sec) 



Affcnuafcr 



*4- 



Noise Yo be 



measured 



cnl'ci'S satTic ear 



Gramophone Audiomei'er. 

 Aural mafchirKj or masking o^ a warbler nolV 



Worbllncj 



Geo iriophone Record 



and electrical 



PicU-up 



EleciYiCnl |_ 



Wave FilVer L 



I (if desircd~i; 



Al'fcnuol'or 



Ear 'pVione wil' 

 oH-sefc«p 



Eor 



Noise fo be 



measured 

 Cnfers some 



Figure 7 



(as already described by means of a condenser microphone and an 

 artificial ear channel) in dynes per square centimeter above a zero 

 of a millidyne per square centimeter. The Barkhausen audiometer 

 is compact and readily portable. 



'' A phoii corresponds to a fourfold change of energy, i. e., to a loudness change of 6 

 decibels. 



149571—33 13 



