12 



HAYES— DETECTION OF SUBMARINES. 



centered and noting whether this shifts the apparent direction to the 

 right or to the left. 



The rule which is generally followed in determining the direc- 

 tion of a sound by a rotating device operating on the binaural prin- 

 ciple is as follows: If the sound appears to come from the right, 

 rotate the receivers in a clockwise direction until the sound appears 



lO 7^ 





Plate II. Methods for determining direction. 



to be centered. If the sound appears to come from the left, rotate 

 the receivers in an anti-clockwise direction until the sound appears 

 to be centered. 



A consideration of Fig. 3, Plate II., shows that this rule is gen- 

 eral. Suppose the sound is coming from the direction of arrow i, 

 it evidently strikes the right receiver first and would appear to the 

 listener to come from his right. Rotating the receivers in a clock- 

 wise direction will at first increase the length of time between the 

 arrival of the sound at the two ears but a continuation of the rota- 

 tion will decrease this time difiference in arrival until finally when 

 sound appears binaurally centered the small arrow at the center of 

 the line joining the two receivers will point in the direction of the 

 sound. If the sound comes from the direction represented by arrow 

 2, it is evident that a clockwise rotation would be employed and 

 when the sound is binaurally centered the arrow will point its direc- 

 tion. In case the sound is coming from the direction represented by 



