HAYES— DETECTION OF SUBMARINES. 33 



removed by comparing the intensity of the sound as given by the 

 port and starboard Hnes since the ship acts as an efficient sound 

 screen. 



From the description it is obvious that the complete compensa- 

 tion of a line of twelve receivers is accomplished in three separate 

 stages. First, the 4 groups of the receivers are compensated by 

 means of four similar compensators. The maximum compensation 

 to be effected in this stage is, in terms of water-path, equal to the 

 distance between two adjacent receivers. Second, these four groups 

 are compensated in pairs by two similar compensators. The maxi- 

 mum compensation to be effected in this stage is, in terms of water- 

 path, equal to one and a half times the distance between two adja- 

 cent receivers. Third, these two groups are brought into phase to 

 give a binaural centering. The maximum compensation to be ef- 

 fected in this last stage of compensation is, in terms of water-path, 

 equal to three times the distance between two adjacent receivers. 



Since the amount of compensation effected in the three separate 

 stages is in the ratio of 2:3:6, it follows that all the compensators 

 will require the same angular setting if the average radius of the 

 grooves for the compensators of the three stages has this same ratio 

 respectively. Under such conditions the seven compensators can be 

 geared together so that a rotation of the binaural compensator by 

 the operator will produce the same angular motion in all, and when 

 a sound is binaurally centered all the compensators are so adjusted 

 that the intensity of the sound is a maximum. The compensation, 

 which as described requires seven separate compensators, is all ac- 

 complished by a single compensator known as the " Type H," the 

 principle of which is shown in Plate XIII. 



The four groups of three receivers each connect through the bot- 

 tom plate of the compensator to the points represented by numerals 

 I ••• 12. The path from receiver i includes the groove from i 

 through s and back to A in the movable upper plate of the compen- 

 sator while the path from receiver 3 includes the groove 3-7'-^^. 

 Receiver (2) connects directly to point 2 on the compensator plate 

 through a path length equal to that of receivers i and 3 when each 

 groove path is the same. The other three groups of three receivers 

 are similarly connected to the grooves of the other three quadrants. 



PROC. AMER. PHIL. SOC, VOL. LIX, C, MAR. 20, I92O. 



