Abstract: 1. Apparatus for protecting a vessel from a waterborne missile launched urwater by air pressure, comprising means for continuously listening to port and to starboard at three spaced locations at predetermined progressive distances astern of the vessel for any waterborne wavefront radiated as a consequence of a waterborne missile launching, and for detecting the passage of such wavefront across each of said spaced locations, means for signalling aboard the vessel the passage of such wavefront across any of said locations, and means for recording on a time base the instants that such wavefront crosses each of said locations and the approximate arrival direction of the wavefront in terms of port or starboard, whereby proper evasive action for the vessel may be determined and taken.

Abstract: An acoustic distance measuring device using a predetermined frequency shift keyed bit pattern as the acoustic signal transmitted and received. A phase lock loop detector is provided. Variations in lag from the time required for the loop to lock are eliminated and the remainder of the FSK bit sequence is detected and accumulated in response to changes in the phase detector output. Preferably the FSK bit sequence is generated via radio frequency transmitter from a first location and reproduced and transmitted acoustically from a second station back to the first station.

Abstract: In a target equipment in which transducers are provided to detect the pressure wave generated by a projectile the transducers being connected to a timing and calculating device adapted to calculate from the time delays between the instants of reception of the pressure wave the trajectory of the projectile, a signal transmitter, comprising a spark generator, is used to transmit sonic signals which are detected by the transducers. The signal transmitter can be used to indicate the precise location or shape of the target and this information is stored in the computer memory.

Abstract: A side scan sonar system comprises a sonar transmitter transducer means for transmitting sonar signal pulses so as to produce an arc of insonification extending to one side of a line along the direction of forward motion of a ship. A line array of receiver transducers for receiving echo signals within the arc is also provided. An electronic scanning beamformer is adapted to combine the signals of the transducers of the line array so as to form a directional receiving beam and to steer the beam electronically through a scanning angle within the arc of insonification. A sampling means is arranged to receive the combined signals of the transducers. A sampling control means is synchronized with the transmitted pulses and is operative to control the sampling means to select signals appertaining to a predetermining sector or strip within the scanning angle. The signals provide information signals for a visual display means.

Abstract: Acoustic beacon for use at sea and having a pipe-shaped housing in the one nd of which is space for a battery which drives a transmitter disposed coaxially around the housing at the other end where there is arranged a pressure switch covered by a membrane. The transmitter is switched on by the pressure switch when the pressure on the outside of the membrane exceeds a certain limit when the beacon falls in water.

Abstract: The method and apparatus for computing the range to and depth of a submerged object that either emits or reflects pulses of acoustic energy, wherein a detecting array and related data handling apparatus measure as a function of time the apparent angles of arrival of the acoustic energy associated with each such pulse. This data is then translated into actual multipath arrival angles and multipath travel time differences which are utilized to solve mathematical equations, the solutions of which result in the calculation of the range to and depth of the submerged source of acoustic energy.

Abstract: An ambient sea noise elimination system is disclosed in which the outputs of a directional hydrophone and an omnidirectional hydrophone are filtered and summed such that the effective receiving pattern below approximately 300 Hz is a vertically oriented dipole pattern having a null in the horizontal direction and such that the effective receiving pattern above 300 Hz is a cardioid having its null either pointing upwardly or pointing downwardly in a vertical direction. The option of simple omnicoverage at the high frequencies can also be easily implemented. This system thus takes advantage of the discovery that ambient sea noise under 300 Hz primarily travels in a horizontal direction whereas ambient sea noise above 300 Hz generally travels in a vertical direction.

Abstract: A method of and apparatus for locating an object by stress wave energy reflection in which the wave energy is transmitted as a beam by transmitting transducer elements, and is scanned through successive sectors of a field of view by imposing differential transmission delays on transmitting signals fed to the elements by means of a delay line. Indicator signals are developed in receiving channels connected respectively to receiving transducers providing binaural characteristics, and transducer providing monaural characteristics but collectively covering the field. An indicator means comprises any, or any combination, of audible means, visual means or tactile means the two latter providing coordinate displays.

Abstract: An acoustical sensor utilizing fiber optic transmission including an optical signal generator, a first single-fiber transmission line connected to the generator, and a coupler for receiving signals from the first line and transmitting the signals to a second single fiber which directs the signals to an acoustically sensitive reflective surface. The surface modulates the signal in accordance with acoustical signals applied to it and reflects at least part of the signal back to the fiber where it is transmitted to a third fiber by the coupler and then transmitted to an electronic receiver.

Abstract: A scan converter is disclosed for use in a sector scan type ultrasound imaging system in which ultrasound echo signals return from targets along a plurality of radial scan lines distributed in a sector field with a substantially equal tangential angular increment with respect to a reference line. The scan converter comprises a sampling circuit which samples the echo signals at a speed inversely proportional to the cosine of the angle of deflection of the radial scan lines with respect to the reference line so that the sampled points align themselves in lateral lines perpendicular to the reference line. The sampled echo signals are converted into digital echo data and stored in a random access memory in the direction of its columns. The stored data are retrieved serially in the direction of the rows and fed into an interpolator for making interpolations between the successively retrieved echo data.

Abstract: Echo ranging apparatus to locate fish, vegetation and structure in the sea modifies signals presented to a recorder in the apparatus so as to enhance the capability of the user to distinguish fish in the vicinity of vegetation and structure, including the sea bed. A transducer receives the reflected echo signals. A receiver stage and amplifier stage present signals which, apart from the modification, would be conventionally useful in aiding the user to locate fish. However, a signal modifier connected at the output of the amplifier stage, between the amplifier stage and the input to the recorder, substantially enhances the capability of the apparatus. It does so by shunting signal reducer circuitry in parallel at the output of the amplifier when the level at the output surpasses a predetermined level, to reduce the signal levels at such output while retaining variations in such signal levels. Such retention, as opposed to, e.g.

Abstract: In a target equipment in which transducers are provided to detect the pressure wave generated by a projectile the transducers being connectead to a timing and calculating device adapted to calculate from the time delays between the instants of reception of the pressure wave the trajectory of the projectile, a signal transmitter, comprising a spark generator, is used to tansmit sonic signals which are detected by the transducers. The signal transmitter can be usd to indicate the precise location or shape of the target and this information is stored in the computer memory.

Abstract: An echo sounder including a unit for transmitting, into a medium, acoustic signals at two slightly differing high frequencies and in the form of pulses, resulting in the creation of an acoustic signal in the medium at a low frequency equal to the difference between the two high frequencies, and a receiving unit including a receiving transducer for receiving echoes of acoustic signals at the difference frequency and a display device for recording the echo signals in accordance with their travel times, the display device having a signal input which is connected with the low frequency receiving transducer, is further provided with a second receiving transducer responsive to high signal frequencies for receiving echoes of acoustic signals at at least one of the two transmitting frequencies, and a member connecting the second receiving transducer to the signal input of the display device.

Abstract: The invention relates to the determination of the position of a self-contained operating apparatus movable along any line of displacement over any immersed structure.A follower apparatus is associated with the operating apparatus, and the position of this follower apparatus, along a line of displacement chosen as the reference line, is determined at any instant. The follower apparatus is displaced by the operating apparatus by servo-control means, and at any instant the transverse distance between the operating apparatus and the follower apparatus is monitored.

Abstract: An ultrasonic rangefinder providing a correct distance measurement and comprising a first transducer for transducing electric signals into ultrasonic waves and transmitting the ultrasonic waves, a second transducer for receiving the ultrasonic waves and transducing the ultrasonic waves into electric signals, a differentiation circuit, and a comparator for comparing a level of a differentiated output signal from the differentiation circuit with an output signal level of the second transducer and detecting a threshold time when the level of the differentiated output signal from the differentiation circuit becomes lower then the output signal level of the second transducer where a threshold signal level of the comparator is automatically varied with respect to a time lapse of the travelling ultrasonic waves coming back to the rangefinder after being reflected by an object, thus overcoming the conventional problems due to the spurious-like direct waves.

Abstract: A slamming-resistant sonar dome canoe is provided herein. The canoe generally consists of a shell, e.g., of fiberglass-reinforced plastic e.g., polyester resin with an extensive internal reinforcement of plastic foam, e.g., epoxy foam in the bottom of the canoe, buttressed by an additional but simple lightweight metal framework e.g., steel or aluminum at the mounting flanges and in the upper portion of the canoe interior and preferably bonded thereto by the thermosetting polyester resin. This sonar dome canoe achieves the conflicting requirements for light weight and robustness in a canoe used in a slamming environment.

Abstract: 2.

Abstract: An improved ballistic impact sensing and display system is provided for use in conjunction with land or water ordnance ranges. A plurality of sensors placed around the target area detect the shock wave created by the impact or passage of the ballistic projectile. The sensors drive electronic timing means which record the time intervals between activation of the sensors by the propagating shock wave. Storage registers within the timing means drive a gridwork of display buses arranged along hyperbolic curves. A matrix of indicators bridging the points of intersection of the hyperbolic buses display the compartment within the target area in which the impact occurred. Additional indicators around the periphery of the matrix of indicators display the sector by which a projectile passed if it missed the target area.

Abstract: A lightweight high-power transducer employs an axial array of dual-piston transducer element assemblies which are held in concentric alignment within a rigid cylindrical tube by O-rings set into grooves provided in the periphery of the pistons. The pistons have convex shaped vibratile surfaces which, in combination with the sound transmitting fluid which fills the tubular housing, causes each piston to be effectively radiating into an annular shaped tapered horn whose expanding peripheral annular area terminates into a peripheral opening placed in the circumference of the tubular housing. The combination of the inventive transducer with a tricardioid hydrophone results in a lightweight portable sonar system which achieves long-range target detection with a bearing resolution of 5.degree..

Abstract: A system, which automatically or manually signals and senses the event of a person falling overboard from a vessel (12) into water (14), comprises a portable transmitter (16) coupled to a sound-producing transducer carried by the person (10) for transmitting ultrasonic and/or audible sound waves (18) through the water to a receiver (20) carried by the vessel. The receiver thereby permits rescue operations of the person to be initiated.