Abstract: Methods of subsea communication in which a cathodic protection anode is used as a transmitting antenna. The signals are received at a second location by two electrodes which are spaced apart by different distances from the transmitting antenna.

Abstract: The relative position and orientation between two subsea structures (210, 212) are measured by ultra-short baseline acoustic metrology. Dual mode master/slave (220, 222) stations comprising a multi-transducer array are fitted in known position and orientation relative to each structure. The first station (220) is operated in master mode to determine the position and direction of the second structure (222) relative to the first (220). The second station (222) is operated in master mode to determine the position and direction data from both operations the apparatus calculates relative position and orientation between the structures. The dual mode stations can be replaced by a master station and a slave station, swapping places.

Abstract: A method, probe, and system for detecting presence of cavitation in a fluid and measuring cavitation density and intensity of a specific locale in the fluid. A first cavitation void and associated energy perturbation, produced in a first fluid, moves within the first fluid and is received at a very thin plate, which separates the first fluid from a second fluid and is part of a light-proof chamber containing the second fluid. An energy perturbation in the first fluid is received at the thin plate and produces at least one cavitation void or associated energy perturbation in the second fluid; and the energy perturbation in the second fluid is eventually converted into an electromagnetic signal. This signal is received by a photomultiplier and converted to an electronic signal that indicates the presence of cavitation. The system can distinguish between cavitation voids produced at one location and/or time interval and voids produced at another location and/or another time interval.

Abstract: Locator device that can be used to aid in the recovery of or to provide positional information about a structure that becomes submerged. The locator device for submerged structures consists of one or more modules. Each module can be customized to incorporate one or more features including a power source, a transmitter or source, a receiver or detector, a fastener means, a computer, buoyancy means, a propulsion means, and a communications means.

Abstract: An imaging sonar system develops three-dimensional images of the space below, to the sides, and forward of a ship relative to a fixed frame of reference. Various features permit the system to be used in non-military environments and make possible low cost with substantial capabilities.

Abstract: An apparatus that produces a gaseous vapor baffle that isolates an undersea sonar system from acoustic noise. The apparatus allows for craft carrying undersea sonar systems to travel at relatively high speeds while substantially isolating the undersea sonar systems from acoustic noise interference produced by propulsion systems, hull appendages, waves and bubbles. The apparatus has a support strut that has one end that is joined or attached to the hull of a craft. A sonar pod is attached to the other end of the support strut. The support strut has a ventilation duct and a plurality of ventilation ports. A cavitator is attached to the support strut and produces a sheet cavity as the craft travels in the water. Pressurized air or other gases are injected into the ventilation duct which then exit through the ventilation ports and into the sheet cavity. The pressurized air or gas exiting the ventilation ports expands the sheet cavity to form a gaseous vapor baffle that isolates the sonar pod from acoustic noise.

Abstract: An underwater target tracking capability is disclosed for a grid-search technique utilizing parameter evaluation plot techniques comprising processing acoustic sonar measurements in conjunction with additional kinematics and environmental information. In the implementation described here, the measurements considered are passive broadband sphere bearings together with limiting knowledge of target speed and range at initial detection. These information sources are processed in a manner especially suited to enable rapid response to the emerging tactical situation.

Abstract: A system and method for predicting active, low-frequency sonar array performance in shallow, littoral waters using a physics-based modeling of acoustic reverberation. An operator characterizes the active sonar's acoustic transmitter and receiver, the environment it is operating in and the targets to be detected. The operator selects appropriate bathymetry, bottom composition and sound-speed profile. The spatial resolution of the bathymetry database is enhanced using fractal interpolation and a bottom-loss-and-scattering corrected-for-slope is calculated. A semi-empirical scattering strength is derived from a wind-speed data base and a stochastic biologic realization is derived from a biologic population database. These are then used to calculate a deterministic component of bottom, surface and volume reverberation using a normal mode mathematical model of acoustic wave propagation.

Abstract: A method is provided for automatically characterizing data sets containing data points described by d-dimensional vectors obtained by measurements, such as with sonar arrays, as either random or non-random. The data points are located by the d-dimensional vectors in a d-dimensional Euclidean space which may comprise any number d of dimensions and may comprise more than three dimensions. Large or small sets of data may be analyzed. A virtual volume is determined which contains data points from the maximum and minimums of the d-dimensional vectors. The virtual volume is then partitioned. The probability of each partition containing at least one data point for a random distribution is compared to a measurement of the number of partitions actually containing at least one data point whereby the data set is characterized as either random or non-random.

Abstract: A submarine launched expendable radio navigation system (SSXRN) buoy method and apparatus. According to one embodiment, a method for determining a submarine geographic position using a SSXRN buoy system is disclosed. The method comprising launching a radio navigation-enabled buoy and recording a launch time and DRNS submarine position. The method further comprises recording a buoy breach time and searching for radio navigation RF signals. Then, recording a radio navigation position acquisition time and an initial radio navigation position. Further, recording a subsequent radio navigation position data and a subsequent time. Moreover, determining a DRNS correction factor using a DRNS position error, a buoy drift, radio navigation position data and DRNS position data. In addition, estimating the submarine geographic position using the DRNS correction factor and a DRNS geographic position. In another embodiment, a SSXRN buoy system is disclosed.

Abstract: A submersible, hydrostatic pressure tolerant enclosure for a portable audio device is disclosed. Also disclosed is a removable lid allowing for the inserting and removing of the device from the enclosure. The disclosure further provides a connector system and an audio communication link connecting the housing to a device capable of generating sound, and to a device capable of producing sound while being submerged in an aquatic environment. Also disclosed are headsets containing at least one speaker within a waterproof enclosure. The speakers may be positioned in or near the ear canal, and attached to the ear or to the user's equipment. The headsets may further comprise devices for controlling power and fidelity. The disclosed invention provides an affordable, easy to use and flexible appliance for utilizing an audio device while being submerged into an aquatic environment.

Abstract: A method, probe, and system for detecting presence of cavitation in a fluid and measuring cavitation density and intensity of a specific locale in the fluid. A first cavitation void and associated energy perturbation, produced in a first fluid, moves within the first fluid and is received at a very thin plate, which separates the first fluid from a second fluid and is part of a light-proof chamber containing the second fluid. An energy perturbation in the first fluid is received at the thin plate and produces at least one cavitation void or associated energy perturbation in the second fluid; and the energy perturbation in the second fluid is eventually converted into an electromagnetic signal. This signal is received by a photomultiplier and converted to an electronic signal that indicates the presence of cavitation. The system can distinguish between cavitation voids produced at one location and/or time interval and voids produced at another location and/or another time interval.

Abstract: Underwater position determination is provided by combining sonar-derived ranging data between a sonar receiver and a sonar transmitter with GPS position data to provide geographically-referenced position data accurately representing the position of a sonar receiver carried or worn by a diver or submersible vehicle. Function and accuracy enhancements are provided to compensate for diver and sonar transmitter and depth difference and differences of sonar signal propagation speed as well as several techniques of compensation for change of position of the GPS receiver and for logging diver and/or vehicle path.

Abstract: A method for detecting the ingress of liquid into an empty elongate hollow structure such as a support for an offshore platform which is at least in part submerged in a liquid. Sound is introduced into the structure by a sound generating device mounted within the hollow structure, the device comprising sound generating means and liquid detection means. When the liquid detection means detect an ingress of liquid into the structure, the sound generating means generate a sound in response to this detection. The generated sound propagates through the structure and sound is detected, and detection of the sound giving an indication of liquid ingress into the structure.

Abstract: A sensor for detecting and monitoring scour in sediment positioned beneath a body of water, which includes a probe at least partially embedded in the sediment. Sensor electronics are superimposed on the probe. Such electronics include a reflectometer, a battery supply and a telemetry transmitter to display an interface boundary between the water and the transmitter. The sensor is particularly well adapted for use in lossy soils.

Abstract: A thermal sensor system is provided in combination with a maneuverable vehicle, particularly in an underwater application. The system includes a transport pipe having an intake and output for the passage of seawater. A thermal sensor is connected to the transport pipe for detecting an actual temperature of seawater within the transport pipe. Sensor electronics are provided in connection with the thermal sensor, the sensor electronics conditioning signals output by the thermal sensor. The selective sampling by the thermal sensor may either be intermittent or continuous according to system needs. Further, a control device is connected to the sensor electronics, acoustic equipment and a depth sensor in connection with the maneuverable vehicle allowing change of the vehicle's course in response to these inputs.

Abstract: A method is provided for estimating the size of an object from a region of a fluid medium when that object is emitting acoustic radiation of known wavelength ? on its own or as the result of being interrogated by acoustic pulses that reflect from the object. The acoustic radiation is monitored using a line array of N acoustic receivers such that N signals indicative of the acoustic radiation are generated. M time series summations are formed using the N signals. Each of the M time series summations is formed using a unique time delay predicated on a corresponding unique estimated speed of propagation of the acoustic radiation where M estimated speeds of propagation are defined. For an object in the region having a diameter D on the order of ?, the M values will vary as a function of the M estimated speeds of propagation with the resulting distribution of the M values being indicative of diameter D.

Abstract: Propagation of sound in an ocean is accurately predicted at all ranges from a source by a computational method that uses a newly created Decomposition Method to make the predictions at long range from the source. The predictions are done in a limited region of the ocean without the need to predict propagation of sound outside the region. The vertical boundaries of the region are parallel to a given direction of propagation of sound from the source. These boundaries are transparent, and sound penetrates them without reflection. The Decomposition Method is based on a special splitting of the sound field into primary and secondary components. The primary components are related to the sound field that would exist in the region if the vertical boundaries of the region were acoustically hard. They are found by integrating a system of coupled parabolic equations that are derived from the coupled mode equations for the sound field in the region.

Abstract: A subsea navigation system comprising a plurality of spaced antenna means provided on a subsea structure arranged to emit electromagnetic radiation. A detection means is provided on a subsea vehicle for receiving and analyzing the electromagnetic radiation transmitted by the antenna means allowing the subsea vehicle to navigate relative to the subsea structure. Each of the antenna means comprises a cathodic protection anode provided on the subsea structure.

Abstract: A waterway shield system comprises a plurality of autonomous underwater nodes wherein each underwater node comprises acoustic detectors which may comprise horizontal and/or vertical acoustic arrays which may be directly mounted thereto or extend outwardly therefrom. Each underwater node comprises an acoustic modem for transmitting high resolution acoustic data to a gateway node that provides a connection to a surface system and a network of other underwater nodes in other waterways. The data from the underwater nodes may be utilized to produce acoustic attribute data for hulls of ships in the waterways. An acoustic database is provided that compiles the predetermined acoustic attribute data for a variety of ships and other entities thereby providing previously stored identifying means. The acoustic database is utilized in conjunction with one or more databases of other physical attributes of ships or other objects to thereby provide an automated identification process.

Abstract: The invention provides a method and apparatus for suppressing hydrodynamic cavitation through the use of high frequency (>500 kHz) and high amplitude (>1 atmospheres) acoustic energy. The method includes biasing a transducer driving signal to generate an acoustic field having a positive pressure halves. The resulting acoustic field is imposed on a region where cavitation is to be preempted. A cavitation preempting acoustic field in the liquid is similar in effect as using a hyperbaric confinement for imposing hydrostatic pressure, a known method for suppressing cavitation. In this regime, suppression of cavitation will be due to imposing a dominant high amplitude, high-frequency pressure field to ensure that the gaps between the compressive pulses are shorter than 10?7 to 10?6 seconds, which is less than that typically necessary to cause cavitation.

Abstract: A system (100) and method for identifying a presence of a creature (140) disposed in water (135). This system includes a transducer (105) for receiving at least one vibrational wave and generating at least one transformed signal responsive to the vibrational wave. The system also includes a signal processor (110) for processing the transformed signal to indicate a presence of a particular type of creature which is disposed in water. The system can be included with a buoy, a mooring, an underwater structure and/or a watercraft.

Abstract: Techniques for underwater detection of fully or partially buried objects such as sea mines and underwater cables are disclosed. An acoustical camera produces three dimensional volumetric images of a target area volume of an underwater floor. One or more first images are produced of the target area volume. An acoustical transducer pulse is then directed to the target area volume so as to disturb the loose particulate or elastic matter included in the target area. One or more second images are then produced while the pulse is present in the target area volume. The images can be compared for evidence of buried objects, or to otherwise evaluate objects included in the target area. The camera can be configured with an interferometer mode so as to produce volumetric images at a real-time frame rate.

Abstract: A system for the accurate determination of the position of an underwater vehicle comprising a system observer subsystem having a state velocity update module, a terrain matching module, means for generating a prediction of the terrain matching module's performance and a constrained extended Kalman filter subsystem. The constrained extended Kalman filter subsystem includes a steady state extended Kalman filter, a non-linear constraint module, and a state predictor.

Abstract: Methods and apparatus determine if an underwater intruder passes under a protective boundary. A sonar sensor system comprises a plurality of sonar sensor modules that are spaced on a protective boundary. A sonar sensor module comprises a sonar transducer (sonar array) that is characterized by an omni-directional radiation pattern that may overlap an omni-directional radiation pattern of an adjacent sonar sensor module transducer. The sonar sensor module collects sonar data such as range information of the target in relation to time. A central processor obtains the sonar data from each sonar module through a telemetry link. The central processor processes the sonar data from the plurality of sonar sensor modules in order to determine an estimated path of the target and may determine if the target should be considered as a threatening underwater intruder from a calculated threat level estimate based on this data.

Abstract: An apparatus for providing Global Positioning System (GPS) position data to an underwater diver for use in navigation is comprised of a SCUBA Flag/Antenna Float, positioned on the surface of the water, containing a Spring-loaded Cable Reel which is connected via a Signal Umbilical Cable to a GPS Capsule carried by the underwater diver. A GPS Antenna and power supply provide a signal to a GPS Receiver/Display which is encased in the GPS Capsule. The diver views icons displayed on the GPS Receiver to determine his/her current position in relation to previously entered waypoints, or geographical coordinates, such as a wreck, dive boat, or locations of interest plotted by the diver during the dive. The position information displayed by the GPS receiver enables the diver to navigate to and from the various locations or geographical coordinates while submerged.

Abstract: Apparatus (50) for deploying an object to an underwater target position, the apparatus being provided with a beacon to transmit acoustic rays, a plurality of thrusters (56(i), i=1, 2, . . . I, I being an integer) to control positioning of the apparatus with respect to the underwater target position, and a sound velocity meter to measure velocity of sound in a fluid surrounding the apparatus.

Abstract: Methods and apparatus determine if an underwater intruder passes under a protective boundary. A sonar sensor system comprises a plurality of sonar sensor modules that are spaced on a protective boundary. A sonar sensor module comprises a sonar transducer (sonar array) that is characterized by an omni-directional radiation pattern that may overlap an omni-directional radiation pattern of an adjacent sonar sensor module transducer. The sonar sensor module collects sonar data such as range information of the target in relation to time. A central processor obtains the sonar data from each sonar module through a telemetry link. The central processor processes the sonar data from the plurality of sonar sensor modules in order to determine an estimated path of the target and may determine if the target should be considered as a threatening underwater intruder from a calculated threat level estimate based on this data.

Abstract: A multi-functional underwater device for use by scuba divers for communicating with and tracking the relative direction of one or more other divers. The device is configured to monitor and communicate with multiple other devices simultaneously and includes a transmitter and receiver assembly for transmitting location signals to and receiving location signals from other communication devices on frequencies defined by a communication channel setting for the device. A processor processes signals to determine separation distance between the devices and to compare separation distances to a safety distance. A display assembly indicates communication channel and safety distance for the communication device and indicates when the separation distance is exceeded. The display assembly includes an input portion operable to set the safety distance and/or the communication channel.

Abstract: A submersible, hydrostatic pressure tolerant enclosure for a portable audio device is disclosed. Also disclosed is a removable lid allowing for the inserting and removing of the device from the enclosure. The disclosure further provides a connector system and an audio communication link connecting the housing to a device capable of generating sound, and to a device capable of producing sound while being submerged in an aquatic environment. Also disclosed are headsets containing at least one speaker within a waterproof enclosure. The speakers may be positioned in or near the ear canal, and attached to the ear or to the user's equipment. The headsets may further comprise devices for controlling power and fidelity. The disclosed invention provides an affordable, easy to use and flexible appliance for utilizing an audio device while being submerged into an aquatic environment.

Abstract: An autonomous mine detection and neutralization system including a motorized underwater vehicle having a guidance control component, and a vehicle positioning system attached to the vehicle via a communications cable. The system also includes a buoyant surface unit comprising a protective housing surrounding an interior chamber, a positive buoyancy buoy attached to the housing, an antenna system attached to the housing, and a radio transmitter and receiver system positioned within the chamber, which radio transmitter and receiver system is electrically attached to the vehicle positioning system and the antenna system. The mine detection system is launched into a body of water from an air craft or surface vessel. The vehicle then proceeds to an underwater target on its own, relaying navigation data and imagery through a communications cable to a surface unit which relays the information over a radio frequency link to a remote user.

Abstract: A system for sonically probing a seabed comprises at least one row (14) of transducers (22) that each can produce a sonic beam, and at least one sonic detector (24). Each transducer is independently energized to produce a narrow sonic beam (40), with resulting seabed or subsea echoes being detected to produce one pixel of a display (60, 80, 90, 150) formed by an X-Y array of pixels, before a next transducer is energized and its echoes are detected to produce another pixel of the display. When the system detects a large change in echo amplitude at adjacent seabed locations, then scanning at those locations is accentuated by analysis and by additional sonification at different frequencies. The transducers are closely spaced, at a center-to-center distance (G) of less than 25 cm, to provide good horizontal resolution and usually lie within 6 meters from the seabed. Each transducer is energized to produce a sonic pulse which, dependent on the application, has a carrier frequency (32) of at least 200 kHz.

Abstract: A sonar system and method are provided to extract and identify information about a particular target illuminated by an active sonar system. The present invention utilizes a Volterra Series Expansion in conjunction with a least squares procedure to estimate channel and target responses, which may be linear or nonlinear. The system estimates the channel and target responses for different orders of the Volterra Series Expansion and then selects the order for which a minimum error is determined with respect to a measured acoustic return signal. The system requires as inputs only the excitation waveform and the measured acoustic return signal.

Abstract: A real-time, three dimensional, acoustical camera and a real-time, range-gated, intensified, electro-optical camera have substantially overlapping fields of view for co-registered imaging of underwater objects at close ranges. The system is typically mounted in an unmanned underwater vehicle but may be used in other fixed or mobile configurations. The coupled fields of view are steerable in an arc around at least one axis over a large field of regard with a servo-controlled rotating mirror system, while the vehicle or the target is moving or hovering. An automated target recognition system uses the multi-modality images to provide enhanced target recognition and/or autonomous operation in unmanned missions.

Abstract: An acoustic array deployment system for an underwater vehicle is provided along with a method for carrying out such deployment. An optical fiber based acoustic array has a first end thereof coupled to a weighted projectile housed onboard the underwater vehicle. A second end of the array is coupled to the underwater vehicle. The acoustic array is maintained in a spooled configuration while the weighted projectile is housed onboard the underwater vehicle. The weighted projectile is forcefully launched from onboard the underwater vehicle in a gravitationally downward direction that is not aligned with the underwater vehicle's direction of travel. As a result, the acoustic array is paid out from its spooled configuration as the weighted projectile is launched and then sinks under its own weight.

Abstract: A subsea navigation system comprising a plurality of spaced antenna means (4) provided on a subsea structure (1, 2) arranged to emit electromagnetic radiation. A detection means (7) is provided on a subsea vehicle (3) for receiving and analysing the electromagnetic radiation transmitted by the antenna means (4) allowing the subsea vehicle (3) to navigate relative to the subsea structure (1, 2). Each of the antenna means (4) comprises a cathodic protection anode provided on the subsea structure (1, 2).

Abstract: A method and system for underwater detection of fully or partially buried objects such as sea mines and underwater cables, consisting of a mobile underwater platform configured with a real-time, three dimensional acoustical camera with a downward directed field of view used as an imaging interferometer, coordinated with a high-intensity, low frequency acoustical transmitter directed as to disturb the loose particulate or elastic matter comprising the seafloor within the field of view of the camera. The images recorded by the camera display the relative motion of the seafloor material before and after an acoustical pulse, in contrast to the lesser or no motion of submerged solid objects. Distinguishing man-made from natural objects is aided by recognizing geometric shapes apparent within the varying image density, not common in nature.

Abstract: Device for subsea metrology of distance and relative orientation of a first termination (10) with a local reference system (xr, yr, zr) and which by means of a jumper spool piece (5) is going to be connected to a separate second termination (20) having a local reference system (xB, yB, zB), characterized by a base metrology unit (2) arranged for being carried by an ROV (4), and arranged for aligned arrangement with the second or the first termination's (20, 10) reference system, and comprising the following features: a wire (3) with an extractable first end (31) being arranged for being attached to a receptacle device (7, 7′) arranged on the termination (10, 20) for receiving the wire's (3) first end (31) or a metrology unit and with a wire tensioner device (32) arranged for tensioning the wire (3) between the base metrology unit (2) and the receptacle device (7, 7′); a wire length sensor (34) arranged for measuring the length (DrB) of the extended taut wire (3); a relative azimuth sensi

Abstract: Provided is a system that allows navigation by GPS while underwater by locating the antenna above water and the display below water. In one embodiment, the GPS antenna is attached to a tow-able buoy having a diver-down flag. In another embodiment, the GPS antenna is carried by the diver and released to float to the surface when the diver wishes to navigate. A preferred embodiment uses a handheld computer to display GPS data, and can be expanded to also calculate and display depth and decompression data, and to provide for further expansion and integration to include other devices.

Abstract: An acoustic array deployment system and a method are provided. An optical fiber acoustic array has a first end coupled to a projectile housed onboard an underwater vehicle. A second end of the array is coupled to the underwater vehicle. The acoustic array is stored on a spool while the projectile is housed onboard the underwater vehicle. The projectile is launched from onboard the underwater vehicle in a gravitationally downward direction that is not aligned with the underwater vehicle's direction of travel. As a result, the acoustic array is paid out from the spool as the projectile is launched and then sinks. By establishing the line array's broadside beam in a direction that is away from the vehicle and approximately perpendicular to the vehicle's direction of travel, the relative angular difference between the underwater vehicle and target can be used to guide the vehicle towards the target.

Abstract: An apparatus for phase coherent underwater communications includes a transmitter; a receiver, including a processor for jointly performing coherent diversity combining, carrier recovery, channel equalization and synchronization; and an antenna array that includes a plurality of antenna sub-arrays for alternately transmitting a signal generated by the transmitter and for receiving an incoming signal. Each of the antenna sub-arrays includes a plurality of underwater sensors positioned such that each of the sensors is spaced at about one half the wavelength of the receiver/transmitter operating frequency from any adjacent sensor in the same sub-array. At least one of the sub-arrays has a centerpoint vertically spaced apart from a centerpoint of an adjacent sub-array at a distance about equal to or larger than a vertical correlation length of a received signal. The individual sub-arrays are beamformed, e.g. using a plane-wave delay-and-sum (or phase-steering) method.

Abstract: A method and apparatus for analyzing newly acquired and faded or lost sonar contacts. Initial processing identifies a list of possible associations between a newly acquired contact and lost contacts. Subsequent processing of the possible associations reduces the number of possible associations that a sonar operator must consider in determining whether an acquired contact represents a new contact, a reacquired lost or faded contact.

Abstract: A trolling motor having an integral sonar transducer including: a submerged motor housing; an electric motor housed in the housing; a sonar transducer housed in the housing; a motor controller having a pulse width modulated output and a shielded electrical cable connecting the sonar transducer to a sonar device. Noise from all sources (i.e., electrical noise from ground loops, radio frequency interference, and magnetic interference) is suppressed in the output signal of the transducer through a number of techniques. The electrical cable includes an outer shield connected to the chassis ground of the trolling motor; an inner shield connected to the circuit ground of the sonar device; and a pair of signal carrying conductors comprising a twisted pair. In addition, the resonant frequency of the transducer is selected such that it is not a harmonic of the operating frequency of the pulse width modulated output of the motor controller.

Abstract: A communications node includes a controller for 1) initializing a counter and resetting a FIFO buffer; 2) determining if a predetermined number of data packets have been transmitted; 3) transmitting the data packets after the FIFO buffer is partially filled if the number of data packets transmitted is less than the predetermined number, incrementing the counter, and returning to step (2); 4) directing a transceiver to be in a receive mode if the predetermined number of data packets have been transmitted; 5) determining if a command signal has been detected; 6) processing a backlink command if a command signal has been detected, and then directing the transceiver to be in transmit mode, clearing the counter, and returning to step(2); and 7) setting the receiver in a transmit mode if no command signal has been detected, and then clearing the counter and returning to step (2).

Abstract: The present invention relates to a device useful as a controllable variable speed thruster-driven oceanographic profiler for coastal waters for measuring the vertical structure of chosen properties of the oceanic water column.

Abstract: A submersible, hydrostatic pressure tolerant enclosure for a portable audio device is disclosed. Also disclosed is a removable lid allowing for the inserting and removing of the device from the enclosure. The disclosure further provides a connector system and an audio communication link connecting the housing to a device capable of generating sound, and to a device capable of producing sound while being submerged in an aquatic environment. Also disclosed are headsets containing at least one speaker within a waterproof enclosure. The speakers may be positioned in or near the ear canal, and attached to the ear or to the user's equipment. The headsets may further comprise devices for controlling power and fidelity. The disclosed invention provides an affordable, easy to use and flexible appliance for utilizing an audio device while being submerged into an aquatic environment.

Abstract: A system and method is disclosed for retrieving an untethered submarine tube-retrievable UUV in which the untethered submarine tube-retrievable UUV may be retrieved through the torpedo tube of a submarine. The untethered submarine tube-retrievable UUV has a capture cable extending therefrom with a transducer to produce a homing signal. A tethered homing signal seeking UUV is guided toward the homing signal. Capture arms on the tethered homing signal seeking UUV engage the capture cable and guide the capture cable to one of several cable snagging eye-members. The winching cable is then winched back into the torpedo tube thereby drawing the untethered submarine tube-retrievable UUV into the torpedo tube.

Abstract: A plurality of actuators are provided at predetermined intervals on the reverse surface of a predetermined side wall of a swimming pool. When an electric signal corresponding to a sound to be propagated in the water is given to the actuators, the electric signal is converted by the actuators into a mechanical vibration signal to cause vibrations. The actuators are secured directly to the reverse surface of the predetermined side wall by an adhesive or otherwise, and thus the vibrations of the actuators are radiated as a sound in the water of the pool through the side wall.

Abstract: A method for Doppler compensation in a phase coherent underwater communications system includes the steps of receiving a communications signal from a plurality of underwater communications channels, where the signal consists of a sequence of raw data; then applying a Doppler estimation to the data; demodulating the raw data; low pass filtering the demodulated raw data; applying resampling and downsampling to the data at a fractional sampling rate, for n samples per symbol, and generating a synchronized, Doppler-phase-corrected output signal; then applying the synchronized, Doppler-phase-corrected fractionally sampled signal to a phase locked loop and equalizer; then comparing an estimated symbol with a decision symbol and updating a plurality of tap coefficients; and h) outputting decision symbols.

Abstract: A method and system are provided for obtaining acoustic data for use in determining fish populations in shallow waters. The system includes an acoustic source comprising a buoyancy unit, anchor, and a broadband acoustic transmitter, and a cable which connects the buoyancy unit to the anchor and supports the transmitter. The system also includes one or more acoustic receivers employing hydrophones and including a similar buoyancy unit, anchor, and cable. When the source and receiver are (separately) deployed, the respective cables are released so that the buoyancy units rise in the water. Thus, with the source and receiver anchored to the bottom the transmitter and hydrophones are suspended at a depth near the bottom (below the thermocline if there is a thermocline) determined by the cable length released. At this time, acoustic signals are transmitted from the acoustic transmitter to the hydrophones for recording.