The Binaural Location of Complex Sounds 



By R. V. L. HARTLEY and THORNTON C. FRY 



Note: Much has been written on the subject of the binaural location 

 of pure tones but the case of complex sounds has received little attention 

 in recent literature. The purpose of the present paper is to bring the dis- 

 cussion of complex sounds abreast of that relating to pure tones. Those 

 who wish to acquaint themseUcs with the work on pure tones will be inter- 

 ested in reading the theoretical work of the authors and the experimental 

 studies carried out by G. VV. Stewart and students working under his 

 direction. This work has been reported in various papers, most of which 

 have appeared during recent years in the Physical Review and the Physi- 

 kalische Zeitschrift. 



A resume of the present paper is given by the authors in their concluding 

 paragraph. — Editor. 



THE need of determining the location of enemy submarines and 

 aeroplanes during the war brought into use practical methods 

 for locating a sound source which depend upon differences between 

 the sound waves reaching the two ears. This stimulated a general 

 study of the phenomena involved in binaural sound location. The 

 foundation for this study had already been laid in the work of Lord 

 Rayleigh and others, who, following more or less in his footsteps, 

 had accumulated a considerable amount of information of both 

 theoretical and experimental sorts. Of this information almost all 

 that was of a theoretical nature and a considerable portion of the 

 experimental kind dealt only with the location of pure tones, the more 

 complicated and in some respects more important problem of complex 

 sounds being almost entirely neglected. Such advances as were 

 made in the theoretical aspects of the problem during the war were 

 subject to the same restriction so that even to-day no comprehensive 

 theory has been advanced which adequately covers the problem of 

 the location of such sounds as occur in every-day life, and in the 

 practical applications of binaural methods. However, the results 

 obtained with pure tones can be made to throw considerable light 

 upon the problem, and it is primarily from this standpoint that the 

 following discussion is written. 



It may be well at the outset to review some of the outstanding 

 differences between the observed phenomena in the two cases. The 

 accuracy of location is much less for pure tones, as is also the sense 

 of definiteness of the sound image. The location of pure tones is almost 

 wholly binaural as is evidenced by the inability of persons deaf in one 

 ear to locate such a tone. With complex sounds not only is the 

 location by binaural effects more accurate and definite, but also the 

 observer is not dependent on these alone. Persons who are deaf 



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