Particle velocity detector and means for canceling the effects of motional disturbances applied thereto

Claim 1

A NOISE COMPENSATING DEVICE IN COMBINATION WITH AN ACOUSTIC PARTICLE VELOCITY DETECTOR DISPOSED WITHIN A NEUTRALLY BUOYANT OIL FILLED FLEXIBLE STREAMER HAVING A PLURALITY OF STRAIN CABLES THEREIN AND ADAPTED TO BE TOWED BENEATH THE SURFACE OF THE WATER FOR MAKING UNDERWATER SURVEYS OF SUBAQUEOUS GEOLOGICAL STRUCTURES, THE NOISE COMPENSATING DEVICE AND PARTICLE VELOCITY DETECTOR EACH HAVING SUBSTANTIALLY IDENTICAL ELEMENTS COMPRISING (1) AN UPSTRUNG STRUCTURE OF HIGH MECHANICAL IMPEDANCE INCLUDING (2) AN ANNULAR PERMANENT MAGNET HAVING UPPER AND LOWER POLE PIECES SECURED THERETO AND FORMING A CYLINDRICAL MAGNETIC AIR GAP THEREBETWEEN, AND (3) A SPRUNG STRUCTURE OF RELATIVELY LOW IMPEDANCE AND YIELDABLY SUPPORTED BY SAID UNSPRUNG STRUCTURE AND CARRYING A COIL WINDING FOR MOVEMENT IN EITHER OF TWO OPPOSITE DIRECTIONS WITHIN SAID AIR GAP, SAID SPRUNG, STRUCTURE INCLUDING (4) A THIN RIGID DOME MEMBER YIELDABLY SUPPORTED ADJACENT TO AND IN ALIGNMENT WITH SAID AIR GAP FOR MOVEMENT BY THE OIL AT THE PARTICLE VELOCITY THEREOF, (5) THE NOISE COMPENSATING DEVICE BEING ELECTRICALLY CONNECTED TO THE PARTICLE VELOCITY DETECTOR IN OPPOSITION WHEREBY IDENTICAL SIMULTANEOUS MOVEMENTS OF THE COIL OF EACH OF THE DEVICES DUE TO COMMON MOTIONAL DISTURBANCES SIMULTANEOUSLY GENERATES EQUAL AND OPPOSING VOLTAGES, (6) A PERFORATED CASING ENCLOSING THE PARTICLE VELOCITY DETECTOR FOR RENDERING THE PARTICLE VELOCITY DETECTOR RESPONSIVE TO PARTICLE VELOCITY OF THE COIL WITHIN WHICH THE DEVICE IS SUBMERGED, AND (7) AN ACOUSTIC SHIELD ENCIRCLING THE NOISE COMPENSATING DEVICE FOR RENDERING THE NOISE COMPENSATING DEVICE UNRESPONSIVE TO PARTICLE VELOCITY OF THE OIL.