-1 VOTCK AND EAR 



309 



conditions, in view of the lar^e range in the impedance values ob- 

 tained for different individuals and at different times the discrepancies 

 indicated are of doubtful importance. In this connection it should be 

 noted that a wide range in impedance values could be obtained readily 

 on the artificial ear merely by changing the constants of the acoustic 

 networks. In view of the fact that a fixed condition of the artificial 

 ear is desirable for many practical purposes the chief requirement as 

 regards the impedance characteristics under discussion is that they 

 closely approximate the impedance characteristics of a typical ear. 



// 

 7^ 



f 



1 - RESISTANCE 



2 - REACTANCE 



3- RESISTANCE 



4- REACTANCE 

 5 - RESISTANCE 

 6- REACTANCE 

 7 - RESISTANCE 

 8- REACTANCE 



OF ARTIFICIAL EAR, SEALED 



OF ARTIFICIAL EAR, SEALED 



OF TYPICAL MALE HUMAN EAR, SEALED 



OF TYPICAL MALE HUMAN EAR, SEALED 



OF ARTIFICIAL EAR, WITH LEAK 



OF ARTIFICIAL EAR, WITH LEAK 



OF TYPICAL MALE HUMAN EAR, WITH LEAK 



OF TYPICAL MALE HUMAN EAR, WITH LEAK 



500 

 FREQUENCY IN 



1000 



CYCLES PER SECOND 



5000 



10,000 



Fig. 13 — Acoustic impedance of ears as viewed through aperture of receiver cap. 



Considerably more data on human ears than are now available appear 

 to be required before an artificial ear with more typical impedance 

 characteristics than those shown can be designed. 



In Fig. 14 additional acoustic impedance data on a typical male 

 human ear and on the artificial ear are shown, the measurements in 

 this case being made looking into the auditory canal. Table II 

 presents data supplementing Fig. 14. As in the previous measure- 

 ments, wide variations were encountered between different ears at 

 any given frequency. The agreement between the artificial ear 



