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BELL SYSTEM TECHNICAL JOURNAL 



natural frequency (/o) and damping (A) as obtained from motional 

 impedance circles for the measurements on human ears vary over a 

 wide range. The results obtained on the artificial ear closely approxi- 

 mate those obtained on what may be considered a typical normal 

 male ear. 



100 500 1000 5000 10,000 



FREQUENCY IN CYCLES PER SECOND 



Fig. 16 — Response-frequency characteristic of deskstand receiver on ears. 



The artificial ear coupled through a suitable amplifier is terminated 

 in measuring apparatus similar to that employed in the sound meter. ^ 

 The indicating instrument used responds to impulses of short duration 

 (under .2 second) in a manner approximating the response of the 

 actual ear to sounds of similar duration. The rectifier, of the copper- 

 oxide type, obeys over its useful range, essentially a square law. 

 By the addition of a suitable loudness weighting network similar to 



^"Indicating Meter for Measurement and Analysis of Noise," T. G. Castner, 

 E. Dietze, G. T. Stanton, and R. S. Tucker. Presented at the Northeastern District 

 Meeting of the A. I. E. E., Rochester, N. Y., April 29-May 2, 1931. 



