Abstract: A device and process is disclosed for creating detailed volumetric ocean els, which in turn are used as inputs for naval tactical and oceanographic analysis. Near-real-time volumetric modelling is accomplished by continuously integrating, filtering, interpolating, and extrapolating oceanographic data (e.g., temperature, sound velocity, conductivity, salinity, bathymetry, current, chlorophyll) from historical data bases, forecasts, remote sensors, and onboard sensors. The value of the invention can be appreciated in the detailed, time-varying, three-dimensional ocean models which can be realized for mesoscale and smaller areas and the ability to use these more detailed and timely ocean models for three-dimensional acoustic propagation predictions and combat control algorithms. Tactical and oceanographic models are computed using an advanced processor and the results are displayed using three-dimensional visualization softwaare and hardware techniques.

Abstract: A digital underwater communication system includes a transmitter and a receiver. An oscillator bank in the transmitter generates a plurality of signals, each having a unique frequency. A timed switching matrix selects predetermined combinations of signals from this plurality and a gate passes only those signals within a selected combination that corresponds to the binary value of a bit to be transmitted. A timer commands the switching matrix to select different combinations at each bit time. The receiver contains a filter bank feeding a plurality of channels, each responsive to a different one of a plurality of signals generated in the oscillator bank. A receiver timer, synchronized with the transmitter timer, enables combinations of receiving channels corresponding to the combinations of signals selected by the transmitter switching matrix during that bit time.

Abstract: Apparatus for detecting sonar signals embedded in noise includes a neural network trained to detect signals in response to the slope of amplitude rank ordered noise corrected powers. A detector detects an analog waveform. Means samples and digitizes the analog waveform to obtain digital samples which in turn are passed through a cosine window. The digital samples are Fourier transformed into conjugate sets of complex numbers representing amplitude and phase. One conjugate set of the complex numbers are discarded, and the remaining complex numbers ranked according to frequency. The sum of the square of the real and imaginary component of each of the remaining complex numbers in a frequency band are provided to obtain a corresponding series of representing estimated power ranked by frequency over the band. The noise contained in subbands of the band is estimated.

Abstract: In an acoustic wave reflector working in the sea, a sheet of air is set up between a reflecting plate and a perforated plate. This sheet of air forms a reflecting interface with the reflecting plate. A rubber bladder forms a container which, under the effect of the pressure of the water, feeds the sheet of air through the perforated plate. The thickness of this sheet of air is kept substantially constant up to the limit of submersion of the reflector. This makes it possible to increase the depth at which the acoustic reflectors are used.

Abstract: The present invention relates to a method and system for scanning a specified underwater area with sonar energy to generate sonar image signals of a submerged diver and othe objects within said underwater area, processing said sonar image signals at, for example, a remote station such as a surface vessel, whereby information is incorporated with said sonar image signals for designating a route from the starting underwater location of the diver to a particular underwater object, and transmitting said processed signals to an image monitor carried by the diver for providing him with visual directional information to assist him in going from his starting location to the location of the targeted object. Preferably, said directional information includes a route or heading line that the diver can follow on his monitor in moving toward the object.

Abstract: An acoustic array, useful for sonar, comprises a plurality of transducing ements which are free floating and not connected to each other. Means are provided for locating the position of each of the transducer elements. The acoustic array may be one-dimensional, that is, a line array, a two-dimensional array, or a three-dimensional array. In another embodiment of the acoustic array, the transducing elements are free-floating but connected to each other by a flexible tether, which limits the range of separation of one transducing element from any of the others. The locator comprises a centrally located element to which there are attached three horizontal rigid arms. On the end of each arm is a high-frequency acoustic transducer. Periodically, each of the transducers transmits a high-frequency broadband pulse. The pulse from each of the three transducers is unique and identifiable.

Abstract: An apparatus and method are provided for an underwater acoustic receiving stem installation in a deep-sea diving helmet. The present invention is directed to a modification of a diving helmet of the type having mixed gas blanking caps for use with miniature hand-held sonar systems operating at depths of 200 feet or more. The invention provides electrical interconnection of an external sonar receiving system to an internal earphone located near the diver's head in the helmet. The invention permits quick connection and disconnection of wiring outside and inside the helmet without breaking water and pressure seals.

Abstract: A transducer projects bursts of ultrasonic energy having broadbandwidths stantially identical to the energy pulses transmitted by a porpoise or dolphin. Immediately prior to the projection of the broadband ultrasonic signals, a range gate pulse is transmitted which, necessarily, first reaches the target and is reflected back toward a hydrophone carried adjacent the transducer-projector. At the termination of the reflected range gate pulse, the reflected broadband ultrasonic signals are gated into a pulse stretcher. During the relatively long intervals between the time that successive bursts of the broadband ultrasonic signals are projected or received, the pulse stretcher functions to translate and divide the broadband ultrasonic signals into signals lying within the audio spectrum.

Abstract: Underwater signal apparatus includes a waterproof housing having two chambers, a sealed chamber in which is disposed a transducer and electrical circuitry associated with the transducer. In the second chamber is a battery for providing the necessary electrical power for the transducer and its circuitry. The battery compartment is accessible for changing the battery. The transducer comprises one wall of the sealed chamber and is thus in direct contact with the water. The transducer circuitry is activated by a magnet movable on the housing. Within the sealed chamber in the housing is a magnetic read switch which is closed by the proximity of the magnet movable on the exterior of the housing.

Abstract: An underwater acoustic transmitter adapted to be released from a submerged ubmarine to float towards the surface of the water and explode a plurality of signalling charges at a predetermined depth in a predetermined time sequence.

Abstract: An underwater control system is disclosed. The system find particular applications in mosaic photographic and/or acoustic mapping of seabed or such marine studies, explorations, etc. A submersible vehicle is tied to a fixed central unit by a tether. The tether winds and unwinds as the vehicle travels in a spiral path, thus covering all the areas of seabed. The vehicle includes a plurality of vertical wings to generate necessary forces to keep the tether taut. In one embodiment, the vertical wings are designed to generate a lift to maintain a substantially constant altitude. In another embodiment, an altitude control device is provided.

Abstract: An underwater signalling device to fire explosives at a preselected depth a prearranged time sequence, which is intended to be part of an underwater sound communication system.

Abstract: A marine mine control wire tagging system is disclosed as including a traitter and a receiver, a mobile underwater vehicle having a launcher mounted thereon, a radio frequency signal tag loaded in said launcher, a sensor and a fire control system for launching said tag upon the detection of said marine mine control wire by the aforesaid sensor. If so desired, said transmitter and receiver may be mounted on a boat which also tows said underwater vehicle to a position in proximity with said control wire.

Abstract: Disclosed is a system for locating a wire that is partially submerged wit water and partially extends out thereof which includes a transmitter for broadcasting radio frequency electromagnetic signals, a phase gradiometer for receiving said radio frequency electromagnetic signals after they have been received by that portion of said wire that extends out of said water and re-radiated by that portion of said wire that is submerged therein and for timely producing a pair of output signals in response thereto, a pair of constant output amplifiers for processing said pair of gradiometer output signals to identical useful levels, a phase comparator for determining the phase relationship between said pair of processed output signals, and a readout for indicating said phase relationship. The aforesaid phase gradiometer may be housed in a probe-type of mobile underwater vehicle which is towed by a tractor vehicle in such manner as to cause said phase gradiometer to traverse an underwater course in search of said wire.

Abstract: A sweep device for river mines of the command type is described. The device mploys two spaced, parallel blades which support the sweep device on the bottom of the river as it is towed therealong. The blades constitute laminated cutting elements which provide a signal of the presence of a command wire as it is severed on contact, as well as serve as electrodes for supplying an electric signal to sweep the mine. An electrical circuit is also described to process the signals from the blades, so as to distinguish between small metallic debris and metallic bodies bridging the two blades.

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: The level of signal noise caused by fluid flow at a pressure transducer, such as a hydrophone or geophone, is determined by measuring the electric field induced when the fluid flow through a magnetic field. The electric field, which is proportional to flow rate, is measured by electrodes positioned about the transducer. The pressure due to the flow is derived from the flow rate voltage by a digital filter which may be adaptive, to allow for varying flow conditions, or which may employ a predetermined electric field/flow noise relation. This flow noise is then subtracted from the received signal, the resultant signal then being substantially noise free.

Abstract: An underwater fuel transfer system for the transfer of liquid fuels such as crude oil from an off-shore underwater mooring to a submerged submarine oil tanker. There is provided a berthing guidance and control system including permanently moored acostic transponders interrogated by the tanker sonar equipment to provide input commands for azmith control along the on-tack position in conjunction with speed controls. The system also includes an arrestor mooring apparatus for decelerating the tanker as the tanker approaches the underwater station. This underwater station has the dual function use of providing mooring for the tanker and also reception of the tanker oil transfer device.

Abstract: A speaker system having a magnet and voice coil are mounted within a dome-shaped enclosure in such a way as to be capable of transmitting sonic vibrations and audio waves through a liquid medium or solid structure, the dome-shaped enclosure cooperating with the magnet and voice coil in such a way as to greatly enhance the waves and sonic vibrations generated to the other medium or structure.

Abstract: Submersible personal stereo using a source, such as a radio, of stereo signals, a pair of sealed chambers housing a pair of electro-acoustic transducer and acoustic transmissive tubing for transmitting sound from the chambers to ear plugs, the tubing being non-wet by water and of a small inner diameter to keep water from entering.

Abstract: High sensitivity interferential electro-optical modulator. The invention concerns an interferential electro-optical modulator. This modulator contains a Mach-Zehnder integrated interferometer in which each interferometer arm (24, 26) is overlapped by an electrode (40, 42), itself surrounded by two lateral electrodes (44, 46, 48, 50) to uniformize the electrical field crossing through each arm perpendicular to the face of the electro-optical crystall on which it is formed. Application to the detection of accoustic waves and low voltage measurement.

Abstract: A remote monitor unit comprising a battery pack, a regulated power supply, program control board, a receiver AD board, a plurality of memory boards and a transducer, all housed in a water tight enclosure. External control or data communication links are unnecessary with the remote monitor unit. Once the device has been activated and placed in its housing, a programmable time delay feature allows the user to place the unit at a selected site in advance of the start of the recording period without wasting any data storage capability. When deployed and activated, analog data from the transducer is converted to digital form and silently recorded by storing it in a non-volatile memory medium on the memory boards. The digitized information is later retrieved from the memory boards by micro, mini or main frame computer and stored on magnetic tape for subsequent processing. The memory boards are then erased by exposure to ultra-violet light and reused.

Abstract: A sound transducer mounted inside a buoy for broadcasting sounds both underwater and above water. The buoy is a hollow sphere which admits water; but whose buoyancy is maintained by air-filled balls or a bladder captured inside.

Abstract: An apparatus for locating, classifying and identifying underwater marine animals by means of the sounds they make includes an elongated submersible array adapted to be towed in various directions. The array is made up of subarrays of multiple hydrophones which are arranged along the length of each subarray in groups. By changing the combinations of groups, the frequency response and the directional sensitivity of the array can be varied. The outputs of the groups can be selectively analyzed both visually and audibly for characteristic fish sounds. The received sounds are classified and used for the identification of newly found fish.

Abstract: A remote oceanographic data recording system which is self-contained batt operated and removably attachable to an external surface of a submerged hull without a need to penetrate said hull is presented. The system is capable of gathering and recording oceanographic data and may be joined to the hull of a submarine without interfering in submarine operation in any way. The system receives analog ac and dc electrical input signals from a variety of oceanographic data sensors and converts the signals to digital data signals for recording on magnetic tape cassette. The housing for the system is watertight and capable of withstanding external hydrostatic pressures up to 1620 psi.

Abstract: A Tactical Expendable Device (TED) adapted to be ejected into the water f a variety of launch platforms and to achieve and remain substantially stationary at a predetermined operating depth for a predetermined time interval or to sink at a predetermined rate for sensing acoustic signals and transmitting such signals to the launch platform through a long, small diameter connecting cable such as a fiber optic filament. The TED system comprises the TED cannister, a long connecting cable, deployment means on the launch platform including a launch tube with integral dereeler, a buffer and onboard signal processing/display equipment. The TED cannister further comprises a sensing element, a buffer, a power source and a dereeling device.

Abstract: An acoustic ocean measuring system is disclosed which uses measurements of sound intensity to locate and measure ocean anomalies. Several free-floating sound pulse emitting floats are placed in the ocean area to be measured; the position of the floats can be determined by well-known ranging techniques. Several hydrophones are positioned either in the immediate area or at distant locations to receive the sound pulses. A fixed number of received sound signals are electronically processed to obtain peak intensity signals. A fixed set of peak signals received from the floats over a fixed period of time are used to generate a trend line which can be used to predict the peak intensity received from the position data. The actual received intensity measurements are compared to the predicted measurements; substantial deviations from the predicted values are used to locate and measure parameters of ocean anomalies.

Abstract: A quick deployment vehicle (QDV) for implanting a transponder or beacon on he ocean bottom in an upright position exposed for receiving or transmitting acoustic signals. The vehicle includes a ballistic body of separable fore and aft sections. The fore section includes a core mass for penetrating the ocean sediment, and the aft section includes a beacon for signal transmission. A predetermined interval after impact, as determined by a programmed deceleration profile stored in memory, the sections will separate. The sensed deceleration of the vehicle is compared at predetermined intervals to the stored profile, and when the sensed level is less than the stored level, a squib is fired to separate the two sections. The aft section penetrates and remains exposed above the sediment, while the fore section further penetrates into the ocean bottom.

Abstract: A funnel construction for a dipping sonar system carried in a helicopter includes the opening to a cylindrical housing of glass epoxy material for storing an underwater transducer which is deployed by suspending it into a body of water at the end of a thin cable. The housing opening includes a flared funnel structure including an entrance aperture member of thin wall aluminum alloy, a backing structure including a frustoconical strut member secured to the bottom of the helicopter and a resilient foam material positioned between and bonded to the entrance aperture member and the strut member which permits the entrance aperture member to move somewhat when impacted by the transducer. The aluminum alloy material in the entrance aperture is very light and yet transfers the heat of friction from rubbing of the small diameter cable against itself sufficiently rapidly that very little wear or damage is caused to either the cable or the funnel structure from repeated high speed reeling cycles.

Abstract: An underwater photographic system which includes an underwater camera enclosure having an underwater sonar range-finding apparatus for providing a signal to adjust the distance-related parameters of a camera enclosed therein. The enclosure is adapted to house typically an unaltered commercially available self-developing or "instant" camera specifically including a camera having an air-sonar range-finding device.

Abstract: This disclosure is concerned with improvements in underwater elapsed time strobe-camera apparatus and the like involving sonar-triggering by a sonar beam generated co-axially with and about the camera lens axis and, as a result of novel circuits, size-reduction and packaging, adaptability for portability, with ancillary novel features of automatic predetermination of number of pictures and indication thereof.

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 hydrophone deployment apparatus is provided for an underwater vehicle, rein the apparatus includes an annular drum releasably mounted about the tail portion of the vehicle. A plurality of arms are pivotally connected to the aft portion of the drum and are capable of swinging from forward positions flush with the vehicle to aft positions behind the drum. A device is provided for enabling retention and selective releasing of the arms from the forward flush positions. A hydrophone is releasably mounted on the inside of one of the arms, and a cable is connected between the hydrophone and the vehicle with an intermediate portion wound on the drum. With this arrangement a release of the arms during travel of the vehicle will cause the drum to be released and the vehicle will swim away from the drum pulling the cable until it is completely off the drum, at which time the hydrophone is pulled from its mounting in the arm. At this time the drum is jettisoned and the hydrophone becomes operational.

Abstract: A thin disk acoustic baffle comprising a thin disk of material having a uue combination of acoustical properties and dimensions to provide optimum attenuation of sound transmission between two points. Optimum sound attenuation is achieved by adjusting the thickness, diameter, and location of the thin disk relative to one of the points to be baffled and by selecting the material of the disk to have acoustic properties such that sound waves diffracted around the edges of the disk cancel the direct waves transmitted through the disk at a particular frequency of interest.

Abstract: A surface acoustic signal defader for optimizing the signal received from derwater sound scattered from the ocean surface. The bandwidth of the underwater sound source is monitored and the frequency of maximum signal strength is identified. When the maximum signal strength frequency fades a predetermined amount, reception is switched to the signal of maximum anti-correlation. This process is continuous such that when the new frequency fades the anti-correlation process will determine the optimum frequency for the new fading condition, thus resulting in optimum reception of surface scattered underwater sound.

Abstract: A hollow, projectile-shaped body containing an acoustical transducer is rased into the sea such that the body descends in free fall until it strikes and penetrates the sea floor, coming to a rest therein. Acoustic signals emanating from the acoustic transducer are processed to generate a direct current analog signal which is a function of the acoustical attenuation of the acoustic signals from a time immediately preceding the body striking the sea floor surface until the body comes to rest in the sea floor, thereby obtaining an indication of the physical characteristics of the sea floor.

Abstract: Apparatus for use with a system in which successive pulses, each composed of a train of high frequency oscillations, are emitted by a transmitting transducer, propagated through a transmission medium, and received by a receiving transducer having a given transient behavior, the apparatus serving to measure the time interval between reception of successive pulses by the receiver transducer and to prevent erroneous measurements resulting from propagation of the pulses over indirect paths through the transmission medium, prevention of erroneous measurements being achieved by effecting time interval measurements only with respect to those pulses for which the output signal from the receiving transducer in response to reception of each such pulse exceeds a selected threshold value during a predetermined time interval subsequent to passage of that output signal above a given comparison value which is less than the threshold value.