14 



HAYES— DETECTION OF SUBMARINES. 



and the direction of the sound. This relation between the path dif- 

 ference and the direction of the sound is readily seen to be: 



d=o.2T, a sin 6, 



where d represents the path difference in air, a the distance between 

 the two receivers, and 9 the angle the sound makes with the line 

 joining the two receivers. 



Since this definite relation exists between path difference and 



3^/C? ~ / 



^ni^^ 







Plate III. Principle of binaural compensation. 



the direction of the sound, a device for varying the air paths can be 

 introduced and calibrated directly in terms of angle. 



Two weaknesses in this method for determining direction are 

 apparent. First, if the angle approaches zero or i8o degrees a large 



