The Physical Characteristics of Audition and 

 Dynamical Analysis of the External Ear 



By R. L. WEGEL 



Synopsis: This paper discusses some of the characteristics of the 

 ear which have become important in the design and development of tele- 

 phone apparatus and circuits. The field of audition, bounded by the 

 curves of minimum and maximum loudness as functions of frequency, 

 has been determined for a large number of ears, and the smaller included 

 area most used in speech has been mapped. The nature of these fields in 

 certain cases of abnormal hearing has also been determined and the condi- 

 tions which must be observed in designing apparatus to satisfactorily 

 relieve deafness are discussed. 



The sensitivity of the ear is given in terms of the r. m. s. pressure 

 measured by a calibrated condenser transmitter. It is printed out in the 

 appendix that this pressure is not necessarily equal to that which, when 

 applied to the ear drum, would just give rise to the sensation of sound. 

 However, it is the nearest approach to the value of this pressure which can 

 be determined at present, and as the dynamical properties of the ear 

 become more fully known it is pointed out how the relation between the 

 two pressures can be more accurately stated. — Editor. 



1. Introduction. It has become important in the design and 

 development of telephone apparatus and circuits to know quantita- 

 tively the various functional characteristics of the ear since the ear is 

 an important dynamical unit in the long series of vibration transmitting 

 apparatus constituting a telephone system. A complete analysis of 

 this problem involves not only the properties of the physical circuit, 

 but also the characteristics of the ear and voice and of the air passages 

 between the mouth and transmitter and between the ear and receiver. 

 It is the purpose of the present paper to discuss some of the character- 

 istics of the ear and its outer air passages. 



Much has been learned about the normal ear by the investigation 

 of the characteristics of abnormal ears. This has incidentally had 

 an application to otological diagnosis and the design and building of 

 amplifying apparatus for the deaf. 



This paper is a summary of the conclusions reached to date regard- 

 ing the absolute sensitivity of normal and abnormal ears, the maximum 

 sound to which the ear can accommodate itself, the much discussed 

 points of "upper and lower frequency limits of audition," the "quality" 

 of audition, a brief mention of the binaural sense and the principles of 

 rigorous dynamical analysis of the ear as a mechanism. A brief 

 description of the apparatus used is also given. 



The function of the auditory sense is to detect sounds of various 

 kinds and wave shapes varying over a range of pressure on the ear 

 drum of from about .001 to 1,000 dynes per cm^ and over a consider- 

 able part of this range to differentiate with certainty between complex 



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