Abstract: An apparatus for preventing the transmission of sound in an underwater medium. A resilient housing encloses at least two voids. A first void contains a compliant tube consisting of two T-shaped support structures, each T-shaped support structure supporting a free-bending span designed to resonate at a predetermined frequency. A second void contains a viscous liquid in which metal fibers are suspended. The resilient housing may be surrounded by a rigid cover material which may include means for fastening the apparatus to a surface. The viscous liquid dissipates sound. The compliant tube attenuates the sound waves and decreases the velocity of the sound waves, consequently decreasing the wavelength of the waves.

Abstract: An underwater acoustical projector has its barrel staves located radially tward of a piezoelectric ceramic driver. The barrel staves are in an hour glass arrangement. The cross-sectional arrangement of the barrel staves is circular at both the top and bottom of the hour glass forming elliptical cross-sections of varying eccentricity between said top and bottom of said staves. The cross-section of greatest eccentricity is located midway between the top and bottom of said staves. The cross-section of greatest eccentricity is located midway between the top and bottom of the barrel staves. This forms a projector with a varying radius of curvature in each of the four 90.degree. quadrants around the axis of the projector. This yields large changes in the resonant frequency.

Abstract: A spring for a seismometer for suspending one body relative to a fixed reference point within a housing including an outer ring and an inner ring interconnected by a plurality of arcuate legs. Each leg has an inner and an outer edge which may be defined by a plurality of arcs of different radii and distinct centers. The plurality of arcs further divide each leg into an inner section and an outer section of approximately equal length, and a middle section of substantially constant width and thickness. The spring provides an improved spurious resonance over the prior art springs as well as having an improved useful life.

Abstract: A method of correcting a seismic signal s(t) provided by a vibration sensor (100) in response to at least one emission signal F(t) produced by a least one seismic vibration generator (200). The real emission signal F(t) differs in phase and amplitude relative to a reference emission signal F(t). The correction method of the invention consists in determining the phase difference .DELTA..phi.(f) and the amplitude ratio A(f) between the real emission signal F(t) and the reference emission signal F(t) as a function of frequency f, and in applying the seismic signal s(t) from the vibration sensor (100) to a filter (304) whose response is defined in phase and amplitude respectively by -.DELTA..phi.(f) and by 1/A(f).

Abstract: A method and apparatus (10) for sensing sound in a fluid medium. The apparatus (10) includes an element (12) for generating polarized light having a predetermined plane of polarization. In addition, the apparatus (10) further includes an element (14) for rotating the plane of polarized light in response to sound waves propagating in the fluid medium, as well as an element (32) for detecting the polarized light. Finally, the apparatus (10) includes an element (34) for generating a signal from the output of the detecting element (32) which is indicative of the amplitude and frequency of the sound waves.

Abstract: This invention concerns a low frequency, high energy output electroacoustic transducer. It utilizes a vibratory unit formed of a stack of hollow ceramic cylinders about which is fitted a resilient metal sleeve. The metal sleeve is tensioned outwardly during assembly of the unit so that, upon relaxation, it will fit about the stack as tightly as possible. To further make the stack and sleeve integral, a bonding material is placed between the two. A gap in the sleeve serves as a cutting guide for gapping the stack. Air backing is used to further increase the energy output of the transducer.

Abstract: In accordance with illustrative embodiments of the present invention as disclosed herein, a leader cable is anchored to a post on the upper end of a geophone case having a spike on its lower end that penetrates the ground to hold the case in an upright postion. The anchor is formed by a continuous stress member in the cable that is looped around the post to isolate the electrical conductors in the cable from strains imposed on the cable. The post can be an integral part of a block located at the upper end of the case, or a bobbin that is captured by a cap that closes the top of the case.

Abstract: A compact, marine acoustical source is disclosed. More specifically, the present invention relates to a marine acoustical source capable of producing a strong primary pulse while substantially suppressing or eliminating undesired secondary pulses derivative from said primary pulse.

Abstract: A method and apparatus for providing shear waves in a marine environment in which a shear wave source penetrates the surface sediment of a water bottom. The shear wave generating source includes an actuator/reaction mass system mounted inside a structural ring of a housing section. A cross-shaped structure at the top of the apparatus serves as a passive reaction mass and as a moment arm support for reversibly motor driven propellers enclosed in shrouds at the outer ends of the structure. A thruster system provides dynamic positioning. The cross-shaped structure and housing section are connected by a structurally stiff member, such as a vertical tube. Pistons provide actuation against a reaction mass located within the housing structure, and motion of the housing structure generates shear waves which propagate in the subsurface formations.

Abstract: An improved cartridge case flash hole uniformer having a hardened self-cleaning reaming and chamfering blade for use either as a hand tool or with a power drive for providing the consistent case to case uniforming of flash holes to facilitate the communication of a uniform bloom of detonating primer flash from the primer pocket by way of the flash hole into the cartridge case power chamber in turn for consistently generating uniform propellant charge ignition, and thereby enhance the cartridge factor accuracy of reloaded ammunition from round to round for match and precision bench rest shooting applications.

Abstract: A retrofit digital electronics unit replaces the analog electronics unit of a tube-launched optically-tracked wire-guided missile. The retrofit digital electronics unit is smaller in size permitting the warhead of the missile to be enlarged. Additionally, the retrofit digital electronics unit is more susceptible to modification through simple changes in software.

Abstract: A geophone configuration is disclosed that includes an elongated extension or spike that couples with the soil in the hole made by the spike in the region near the end of the spike without hard or firm coupling with the soil above that region. A bow spring or drill bit larger in diameter than the diameter of the spike can be used for achieving predominant contact for the coupled region compared to soil opposite the remainder of the spike. Alternately, a weighted tip can be employed to achieve relative superior coupling by weight compared with the less heavy region of the spike above such weighted tip.

Abstract: A piezoelectric transducer having plural piezoelectric transducer elements which can generate mechanical vibrations converging substantially on one point. The transducer is formed to control the convergent point by insulating piezoelectric transducer elements mechanically, arranging them concentrically and driving them independently and separately from each other.

Abstract: A support member preferably made of a metal such as cold rolled steel is disposed in a looped configuration and is provided with a gap. A transducer member preferably made of a piezoelectric material such as a ceramic is disposed within the support member. The transducer member is provided with a gap at a position corresponding to the gap in the support member. A closure member made from a suitable springlike material such as an alloy steel is attached to the opposite ends of the support member at the position of the gap as by welding. The closure member extends in a U-shaped configuration into the looped configuration (in section) defined by the support member and the ceramic member. The axial length of the closure member defines the bandwidth of the frequency vibrations generated by the transducer member.

Abstract: A transducer for an acoustic logging tool includes a liquid-filled cavity formed by a substantially rigid housing portion of the tool and having a resilient barrier member disposed between liquid in the wellbore and the liquid in the cavity. A magnetic field extends transversely through the cavity and a member, which may comprise a rigid plate, a flexible member or a quantity of electrically conductive liquid trapped between flexible membranes, is disposed in the cavity for movement normal to the magnetic field. A voltage is generated in response to movement of liquid in the cavity which is proportional to the velocity of the plate or member, or the velocity of the conductive liquid, the length of the conductive path and the intensity of the magnetic field in accordance with the principles of the Lorentz force.

Abstract: A geophone is disclosed that has a cylindrical housing closed at one end by a bottom and at the other end by a top. A magnet assembly and a coil-mass are located in the housing. Springs support the coil-mass for axial movement relative to the magnet assembly along the longitudinal axis of the housing. A pair of coil terminals are mounted in the upper end of the coil-mass adjacent the top of the housing. A pair of eyelets extend through the top of the housing and outside geophone terminals are attached to and extend through the eyelets into the housing. A pair of pigtails connect the geophone terminals to the coil terminals.

Abstract: A piezoelectric seismic vibrator is disclosed which utilizes a hydraulic system to amplify the longitudinal displacement which results from the application of a voltage to a stack of piezoelectric elements. In each disclosed embodiment of the present invention, a stack of piezoelectric elements is mounted so as to bear upon a power piston which in turn acts upon a high bulk modulus substantially incompressible body of fluid, such as mercury. A drive piston is provided having a cross-sectional area which is smaller than the area of the power piston and the pressure within the fluid system acts to amplify the longitudinal displacement of the piezoelectric elements. The movement of the drive piston is then coupled mechanically or fluidically to the earth to generate seismic waves therein. In one depicted embodiment of the present invention each stack of piezoelectric elements is disposed within a fluid filled chamber which is pressurized by means of communication with the borehole fluids.

Abstract: An acoustic source apparatus has a loudspeaker enclosed within a substantly pressure resistant and water tight enclosure. Acoustic energy from the loudspeaker emanates through an opening in the enclosure. This opening is covered by a resilient diaphragm that transmits the acoustic energy to an aqueous medium. A net constrains the diaphragm to a preselected size and shape. The net further impedes overexpansion of the diaphragm and restrains the diaphragm from migrating due to buoyancy. Additonally, the net stiffens and strengthens the diaphragm, to thereby increase the resonant frequency, impedance and quality factor of the transducer system and decrease the transmission bandwidth of the system. Constraining the transducer diaphragm with the net makes higher transducer source levels possible.

Abstract: A low frequency, high powered underwater sound source includes a housing ing disposed therein, a loudspeaker, a bladder disposed over the loudspeaker for containing a pressurized non-liquid sound transmission medium, a fill system for filling the bladder with a sound transmission medium, a vent system for venting the bladder of a sound transmission medium, a differential pressure sensor for comparing the pressure in the bladder with the ambient underwater pressure, a signal generating system to generate an acoustic signal at the loudspeaker, and a control system for controlling operation of the fill system, the vent system, the differential pressure sensor and the signal generating system.

Abstract: A driving member for a diaphragm in acoustic devices includes a body with opposite recesses into which driving rods are inserted. One end of the driving rods is attached to pressure rods which directly influence the diaphragm and the other end of the driving rods makes contact with the bottom of the recesses.