310 



BELL SYSTEM TECHNICAL JOURNAL 



TABLE II 

 Acoustic Impedance of Ears Looking into Auditory Canal 



O -200 

 O 



500 1000 

 FREQUENCY IN CYCLES PER SECOND 



10,000 



Fig. 14 — Impedance characteristic of auditory canal. 



results and the human ear measurements is as close as seems warranted 

 by the available data. 



The acoustic impedance data presented are important from the 

 standpoint of insuring that the receiver under test on the artificial ear 

 operates under nearly the same load conditions as it does on a human 

 ear. It is also important that the response-frequency characteristic 

 of a receiver obtained on the artificial ear compare well with that 

 obtained on the human ear. In this connection two widely different 

 types of receiver have been studied; one, a moving coil receiver such 

 as is used in the Master Reference System for Telephone Trans- 



