6564 HYDROGRAPHIC MANUAL PaGE 616 



The housing of one of the first Vincent hydrophones was of cast aluminum and it had the following 

 dimensions: 



Inches 



Thickness of end yi 



Diameter of opening 4 



Length of collar lYt 



Inches 



Diameter 8}4 



Length 5 



Thickness of cylinder wall ^6 



Thickness of diaphragm Ya 



The air pressure inside the housing is increased to counteract partly the hydrostatic pressure. 

 An electromagnetic unit is mounted by a single screw on the center of the bottom of the housing. 

 The motion of the housing is transmitted to the armature of the electromagnetic unit by a system of 

 levers, relative motion between the armature and the pole pieces occurring because of the inertia of the 

 electromagnetic unit. The electroacoustic unit that has been most frequently used in this hydro- 

 phone is made by Nathaniel Baldwin of Salt Lake City, Utah. But various other kinds of electro- 

 acoustic units and a specially adapted piezoelectric unit have also been used. 



Comparative tests show that the Vincent hydrophone is somewhat less sensitive 

 than the Dorsey hydrophone, but this can be easily compensated for by the use of 

 additional audio amplification (see 656 (a)). One of the advantages of the Vincent hydro- 

 phone is that it is inexpensive and easy to construct. It was first used at R.A.R. 

 shore stations, but was readily adapted for use with sono-radio buoys. 



A smaller Vincent hydrophone was designed especially for use with sono-radio buoys. The hous- 

 ing is a small cylinder bored from a solid rod of Duralumin. One end of the cylinder is solid, the other 

 being fitted with a watertight rubber plug. The electroacoustic unit is mounted on the inside bottom 

 of the housing. This hydrophone has been submerged to 150 fathoms without injury. This hydro- 

 phone and the rubber sheath and cast-iron shell in which it is usually enclosed for use in R.A.R. 

 (see 6564) are illustrated in figure 138. The housing of the unit has the following dimensions: 



Inches 



Diameter 1% 



Length SYz 



Inches 



Thickness of cylinder wall Ys 



Thickness of cap and end Y* 



The electroacoustic unit used is an electromagnetic type, made by the Automatic Electric 

 Company. It has an impedance of 900 ohms. 



6564. Suspension of Vincent Hydrophones 



The large Vincent hydrophone may be suspended from a sono-radio buoy in one of 

 two ways. One method is to hang the unit directly below the buoy at the desired 

 deptb by means of a cable. A clamp is placed around the housing to which the support- 

 ing cable is connected, and to the bottom of which a weight is attached sufficient to keep 

 the hydrophone submerged. The electric cable is lashed to the supporting cable at 

 regular intervals. Parceling must be used wherever there is a possibility of chafing 

 between the electric cable and other gear. 



Another method of suspension is to anchor the hydrophone separately. The 

 buoyant hydrophone is attached to its own 50-pound anchor above which it floats 

 submerged 4 or 5 fathoms above the bottom. The anchors of the hydrophone and the 

 sono-radio buoy are connected by a cable, and the hydrophone is electrically connected 

 to the sono-radio buoy by a rubber-covered electric cable lashed to both anchors and 

 along the sono-radio buoy anchor cable. The electric cable is run through rubber hose 

 to protect it from chafing against the bottom or the anchors. The distance between the 

 anchors should be about 150 feet. 



The entire assembly must be prepared in advance — the hydrophone anchor with 

 hydrophone attached is lowered first, the cable connecting it with the buoy anchor 

 is stretched taut, and then the buoy anchor is lowered from the vessel. 



