Abstract: A system and a method for counteracting marine fouling of e.g. a vessel hull (1) are provided.Electro-mechanical vibration transducers (2, 3) are arranged in pairs adjacent to fixed (clamped) nodal lines (4) on said hull (1), and are driven in an inverted phase relationship in order to provide a water particle movement in a hull parallel direction right outside said nodal lines (4) in addition to the hull perpendicular relative movements right outside said transducers (2, 3).The invention also comprises a combination of the mechanical system above and a special surface coating which counteracts fouling from other organisms than those influenced by said water particle movement in the infrafrequency range.

Abstract: A method of marine seismic exploration of the strata beneath a body of water comprising the steps of generating a compressional wave in the body of water and sensing the converted shear waves reflected from the strata.

Abstract: This invention is a multiple segment flextensional transducer shell that is easily and quickly manufactured and modified. The shell may comprise two adjustable, flexible plates and two buttress bars or two J-shaped adjustable, flexible plates. When the buttress bars and plates or the J-shaped members are connected together at or near the nodal points of the transducer, the assembled shell will have the same shape as the flextensional transducer shells used in the prior art. The open ends of the assembled transducer shell are covered with flanges and a boot is placed over the shell and flanges to make the interior of the shell air tight.

Abstract: This invention provides a method for fabricating ultrasonic transducer arrays and various transducer arrays produced utilizing such methods. The method includes the steps of cutting a block of piezoelectric material to form a plurality of wafers, each wafer being of a predetermined thickness; forming the wafers into a spaced parallel array with a center-to-center spacing between the wafers substantially equal to one-half of the object wavelength (as this term is defined in the specification); and causing the space between the wafers to be filled with a substance having an acoustic impedance which differs from that of the piezoelectric material by an amount such that the reflection coefficient between the piezoelectric material and the substance is greater than 0.9. The predetermined thickness of the wafers may be equal to one-half the piezoelectric wavelength and the substance between the wafers may be formed at least mostly of air.

Abstract: A sonic generator comprises a resonant bar, a housing and magnetic excitation units connected between the resonant bar and the housing. The magnetic excitation units are connected to the bar using a mounting connection which is a sleeve having an inside diameter slightly greater than the outside diameter of the bar. A resilient elastomer such as urethane is mounted between the sleeve and the resonant member.

Abstract: A method, system and apparatus for producing powerful seismic energy impulses by implosion of an imploding free piston positioned in a container which is adapted to be lowered down into a well in the earth to facilitate the collection of well surveying information about the geological formations of the earth in the vicinity of the well. Holding means maintain the imploding free piston in an initial position or quiescent state, trigger means suddenly release the holding means to cause the free piston to accelerate rapidly from its quiescent state thereby producing a powerful impulse by implosion, damping means arrest the movement of the imploding free piston, and operating means return the imploding free piston to its initial position after completion of its rapid acceleration and damped deceleration. After the imploding free piston is returned to its initial position, the apparatus may be triggered again, as desired, to produce additional powerful impulses by implosion.

Abstract: A baffle for enlarging the field of view of and enhancing collection of radiation for a sensor apparatus having a transducer for receiving radiation within its field of view. The baffle includes a base securable proximate the transducer, and at least one blade element extending from the base outwardly from the transducer. The base element includes a proximal edge transecting the transducer to establish at least two apertures for the transducer for enlarging its field of view. The blade element is reflective for the radiation to enhance collection of the radiation from a periphery of the enlarged field of view.

Abstract: A fast acting electromagnetically operated shutter for protecting an imag system from damaging light, such as intense laser light, comprised of a plurality of vane type shutters driven by magnetically moveable linear racks transferring linear to rotary motion to the midportion of each vane to aid in overcoming inertia. The linear racks are comprised of an upper rack at one end of the shutters and a lower rack at the opposite end of the shutters wherein both upper and lower racks simultaneously move reciprocally together. The racks have gear teeth thereon that are meshed with alternate vanes from first the upper and then the lower racks to transfer opposing directional rotation to adjacent vanes. An electronic shutter control means responds to input damaging light intensity signals impinging light detecting sensor means.

Abstract: An apparatus and allied method for detecting the presence of submerged, possibly distressed swimmers in a body of water employs a plurality of pairs of transducers arranged on opposite sides of the body of water. Pulsed sequential excitation of the transducers is employed to monitor the body of water. A person disposed between a pair of transducers interrupts the transmission of ultrasonic waves. An alarm is triggered upon the interruption of the ultrasonic waves or after a delay to avoid false alarms, warning of the presence and location of a submerged, lingering swimmer even in the presence of other active swimmers in the body of water. The same apparatus can be employed as an intrusion detector to detect unauthorized entry of a person into an unguarded body of water.

Abstract: A flextensional transducer provides a low resonance frequency by having its shell portions connected to its ends by a pin- or rotation-type hinge whereby the motion of the ends of the transducer caused by energization of the transducer drive is transferred to the shell portions by the hinge. The reduction in the resonance frequency is achieved by the shell portions acting as a hinged plate whose ends rotate relative to the transducer ends rather than being cantilevered as in the prior art.

Abstract: A distributed geophone data acquisition system is disclosed that includes a receiver for the geophone data and a plurality of data cables connected together and to the receiver at one end. The cables have a plurality of twisted pairs of electrical conductor channels and two fiber optic light guides. Multiple geophone takeouts are connected to separate channels of the cables. Remote data units are connected between adjacent ends of each data cable that convert the geophone signals on each channel to light signals for transmitting through the fiber optic light guide of the next cable to the next remote data unit and ultimately to the receiver.

Abstract: An anti-bounce device for avoiding the multiple shocks of a moving mass after a first impact against another element. Magnetic arrangements are associated with element for exerting an attractive force on the mass sufficient to prevent possible bouncing. These arrangements comprise, for example electromagnets and circuits for connecting the electromagnets to a current source via a switch. Permanent magnets may also be associated therewith. The direction of the electric current is then chosen so that the electromagnetic forces developed are added to the attractive forces of the permanent magnets or else for cancelling these latter out, which allows the mass to be released.

Abstract: The disclosure relates to a solenoid valve for an air gun which substantially increases the rate at which maximum air flow is achieved. The new valve structure includes a coil actuated plunger, which is preferably solid and formed of a magnetically permeable material and closes an annular 360 degree port opening between the valve inlet and valve outlet when in the unactuated state. This plunger position is maintained by a biasing spring which forces the forward annular sharp plunger edge against a face seal in the nose of the valve, thereby sealing the valve input port from its output port. Upon actuation of the solenoid valve coil, the plunger is moved against the bias of the spring very rapidly, thereby speedily uncovering the channel between inlet and outlet and permitting rapid 360 degree communication between the inlet and outlet to permit maximum air flow therebetween and out of the outlet port.

Abstract: Air wave noise caused by a vibrating baseplate on a seismic vibrator is reduced or eliminated through active cancellation of sound. In active cancellation, the detection of acceleration of the baseplate is used to form a counterpart wave which is equal in amplitude but opposite in phase; a speaker produces an opposite air wave to cancel the baseplate air wave.

Abstract: The present invention provides a pressure compensated communication system having at least one audio transducer, the pressure compensated communication system comprising a fluid tight housing for the or each audio transducer, the or each housing having a corresponding one of the or each of the audio transducers located therein and having an orifice coupled to a pressure compensation means, the pressure compensation means connected to the or each orifice and to a continuous supply of gas at a pressure equal to or slightly greater than the pressure of liquid surrounding the housing.

Abstract: A transducer mounting system for permitting the remote pivotal actuation of an underwater signal transducer. The mounting bracket permits a wide variety of transducers to be mounted upon a conventional trolling motor and remotely actuated by an operator in the boat. Actuation of the bracket directs the transducer of a conventional fish locator or depth finder of the acoustic variety for locating fish or other objects therearound. By securing the bracket to the trolling motor, one axis of orientation of the transducer is automatically indicated by the orientation of the trolling motor. Concomitant angulation of the bracket and transducer affixed thereto will thereby permit the operator to precisely locate desired objects such as fish in the direction indicated by the trolling motor.

Abstract: In a tubular pressure transducer element, the axial stress imparted to the element is reduced relative to the radial stress by inserting a rigid core inside the tubular element. The reduction in stress is proportional to the ratio between the area of the full diameter of the tubular element and the area of the annulus represented by the wall thickness of the tubular element.

Abstract: A hydrophone having a self-contained means for warning an operator that the hydrophone has reached or exceeded a safe design depth limit. The active elements of the hydrophone are bender-type piezoelectric wafers. An internal stop is provided such that in the presence of a hydrostatic pressure that exceeds a safe design limit, the wafers bottom out against the stop. The stop short-circuits the electrical output signals of the wafers, warning the operator that the hydrophone is in danger of destruction.

Abstract: A device for generating acoustic waves in a well by causing a mass falling inside a body to strike a target element and to transmit impacts to the surrounding geological formations by anchoring the body in the well by retractable shoes. A tractive force exerted on the support cable from the surface, after anchorage of the body, causes a support element to move upwards which takes the target element and the mass with it. When the mass is hydraulically locked in its set position, the cable is slackened so that the target element and the support element can come back to the bottom position. In this position, the support element presses on a pusher element which actuates hydraulic locking and releases the mass.

Abstract: Air wave noise caused by a vibrating baseplate on a seismic vibrator is reduced or eliminated through passive absorption of sound. In passive absorption, reduction of air wave noise is achieved by building a rigid, light-weight enclosure for the baseplate which remains isolated from the induced ground vibrations and nonresonant.