Abstract: A case 1 is formed of thermoplastic resin, and includes an upper case 11 and a lower case 21. The case 1 accommodates a pole piece 31, a coil 41, a magnet 51, a diaphragm 61, and so on. The pole piece 31 includes an core 32 and a base 33, and placed on the lower case 21. There are integrally formed on an upper face of the lower case 21, a wall 22 for defining a mounting position of the pole piece 31, a projection 23 for preventing a conductive wire 42 drawn our from the coil 41 from getting in touch with the base 33, and a bobbin part 24 for the conductive wire 42 to be wound therearound. A height of the projection 23 is set at an equal or larger value to or than a height of a surface of the base 33, and a contact of the conductive wire 42 with the base 33 can be avoided by the projection 23.

Abstract: A free-floating altitude stabilized system is provided. Independently energizable wire coils are linearly aligned with one another in a vertical direction on a buoyant body. An induced magnetic field is generated by any of the wire coils that are energized. A float housing a magnet is coupled to the body in such a way that it is capable of independent movement relative thereto. A control system energizes a selected one or more of the wire coils in such a way the magnet's magnetic field and wire coil's induced magnetic field react with one another to generate movement of the float vertically in a direction that is the same as a vertical component of wave motion.

Abstract: A system and method for determining a sound speed profile of a water column. A free falling sound source is deployed in the water at a known location and time. The sound source transmits acoustic pulses omnidirectionally therefrom at predetermined times after deployment. An acoustic receiver located at a known location detects each acoustic pulse. The time differential between each predetermined time and a time of arrival for each subsequent acoustic pulse is determined. Speed of sound for each portion of the water column is then determined as a function of the time differential, the known locations of sound source deployment and the acoustic receiver, and the known rate of descent of the sound source. The sound source can be constructed from a hydrodynamic body housing a power source, timing electronics, and spark gap electrodes. A bubble, generated by the spark gap electrodes, implodes to create the acoustic pulse.

Abstract: The present invention provides a pressure-balanced inertial valve assembly for use in marine seismic energy sources such as air guns. The valve includes a poppet having a first seal and a second seal. A pressure chamber containing a fluid under pressure communicating with the first and second seals to substantially balance the pressure across the seals. An inertial mass is coupled to the poppet. A coil assembly is disposed about the inertial mass. A central guide pin provides guided movement for axial translation.

Abstract: The need for multiple, cost-effective deployment of an underwater camera has resulted in the development of a low-power high-resolution imaging system using a sparse array. The system can be used for undersea acoustic mine-field reconnaissance and mine-hunting systems for example, this imaging sonar is portable enough for use in a diver's hands or in a remote imaging sonar on an unmanned undersea vehicle in shallow waters. The present system can simultaneously focus many signals using multiple CCD/CMOS, programmable time-delay beamforming circuits connected to a sparsely-populated 2D acoustic array, is being developed. Using this approach, a real-time image can be formed to search for mine-like objects. To make a sparse array, the combination of low insertion loss and wide bandwidth performance is important for realizing acceptable imaging performance with low illumination levels.

Abstract: A firearm discharge detection device and alarm system featuring a plurality of detector units placed inside a structure which communicate with a central monitoring unit. Each detection unit will detect the discharge of a firearm in its proximity from decibel levels and duration using on board filters and timers and thereon signal the central monitoring unit. A digitized embodiment may also be used to determine the sound of a firearm using a digitized fingerprint of the sound compared to an library of firearm sounds in onboard memory by a microprocessor. The central monitoring unit will thereupon communicate with all the other detection devices installed to sound an audible and/or visible alarm to occupants to exit. Concurrently the central monitoring unit will communicate the firearm discharge and location to police. An optional directional exit alarm or warning to hide may also be activated.

Abstract: There is provided a fiber-optic hydrophone having a compliant sensing mandrel coaxial with and adjacent to a rigid reference mandrel. A first optical fiber is wound around the compliant sensing mandrel and a second optical fiber is wound around the reference mandrel. The first and second optical fibers comprise different arms of an interferometer. Flexible sealing members, such as O-rings, seal the compliant sensing mandrel to the hydrophone. One O-ring is disposed near each end of the sensing mandrel. A cylindrical support member is disposed inside the sensing mandrel. At least a portion of the support member is spaced from the sensing mandrel so as to provide a sealed cavity between the sensing mandrel and the support member. The sealed cavity is filled with air or similar compliant substance.

Abstract: A submersible loudspeaker including an electro-acoustic transducer which accepts the electrical signal from the audio system and delivers sound waves generated by piezoelectric elements in proportion to the signal applied to it. The speaker primarily comprises at least one transformer operatively connected to a piezoelectric ceramic element to form a sound element array, contained within a waterproof sealing body comprising a diaphragm for transducing sound waves to the receiving medium, and encased within a shell or housing. The piezoelectric element is in contact with the diaphragm that directly contacts the transfer medium. The submersible loudspeaker is designed to be used in swimming pools, spas, hot tubs, bathtubs, saunas, ponds, lakes or other bodies of water. A system would include a submersible loudspeaker used in conjunction with an air speaker on a single audio output system, so that a listener can simultaneously listen to music underwater and in the surrounding air.

Abstract: The present invention provides signification improvements over the apparatus and method disclosed by U.S. Pat. No. 4,922,467. The invention provides an apparatus for material classification and substance identification of an object contained within an enclosure, or buried beneath the ground. The improvements to the present invention include the use of a source of either electromagnetic or acoustic energy, and electromagnetic or acoustic energy receivers, as appropriate. In addition, the present invention discloses the use of energy pulses of differing frequencies, such that the signal processor can compute the rate of change of energy absorption of the substance, as a function of frequency (d&agr;/df). In this way, the apparatus permits the formulation of a highly detailed and accurate object signature, which can be compared with a database of known object signatures for exact substance identification.

Abstract: An acoustic transducer is disclosed including: a fixed perforated member; a freely movable diaphragm spaced from the perforated member; a support ring in the perforated member maintaining the proper spacing between the diaphragm and the perforated member near the perimeter; means of suspension allowing the diaphragm to rest freely on the support ring and yet mechanically decouples the diaphragm from the perforated member; means of applying an electrical field in the space between the perforated member and the diaphragm; means of detecting the change of electrical capacitance between the perforated member and the diaphragm when the diaphragm moves in response to an incident acoustic sound pressure wave.

Abstract: The present invention relates to a positioning system for use in underwater/subsea hydrographic surveying and positioning applications The system comprises a submersible having a transponder formed and arranged for communication with a remote receiver. The transponder is formed and arranged to transmit a continuous water propagatable data signal, which signal includes a binary signal sequence, preferably a “gold code”, each of the transponder and the receiver being provided with an internal clock. The clock on the receiver and transponder are in substantial synchronisation. The remote receiver is provided with processing means for determining the position of the submersible by calculating the time taken for a signal to be transmitted by the transponder to be received by the remote receiver utilising the clock time of transmittal with respect to the clock time of reception at the remote receiver. Means for determining clock variation and resynchronising the clocks is described.

Abstract: A folded Sagnac fiber optic acoustic sensor array operates in a manner similar to a Sagnac interferometer but uses a common delay path to reduce distributed pickup in downlead fibers. The fiber optic acoustic sensor array is used to detect acoustic waves in water. By basing the folded Sagnac sensor array on operating principles similar to the Sagnac interferometer rather than basing the array on a Mach-Zehnder interferometer, the sensor array has a stable bias point, has reduced phase noise, and allows a broadband signal source to be used rather than requiring a more expensive narrowline laser. A large number of acoustic sensors can be multiplexed into the architecture of the folded Sagnac fiber optic acoustic array.

Abstract: A method and apparatus for detecting, processing and tracking sonar signals to provide bearing, range and depth information that locates an object in three-dimensions underwater space. A Twenty Six Nearest Neighbor Peak Picker (TSNNPP) is disclosed that improves the detection of signals in noisy background by differentiating bandwidth (BW) characteristics of signals from BW characteristics of noise.

Abstract: A controlled simulation of an underwater target for testing and evaluating a sonar system. The target simulation system receives an acoustic test signal and generates a simulated reflected signal emulating the test signal reflected from a target of known target strength. The system includes hydrophones and projectors located underwater and a signal processing system located out of the water. The signal processing system detects the test signal received by the hydrophone and converts the test signal to digital format. A computer modulates or weights the digital signal using a target strength value representing the target strength to produce a digital representation of a simulated reflected signal. This simulated reflected signal is converted to an analog format and is retransmitted as a simulated reflected acoustic signal using the projector. The level of the simulated reflected acoustic signal can be increased or decreased to simulate various sizes of the same target.

Abstract: Signals from microphones 1, 2 are first stored in memory circuits 4, 6 and then supplied to a cross-correlation arithmetic circuit 7, following which a cross-correlation operation is carried out and cross-correlation function values are calculated for each time difference. An evaluation function circuit 8 carries out addition processing of particular time intervals based on the cross-correlation function values and then searches for the maximum value to calculate time differences. Signals from the microphones 2, 3 are first stored in memory circuits 6, 5 and then supplied to a cross-correlation arithmetic circuit 9, following which a cross-correlation operation is carried out and cross-correlation function values are calculated for each time difference. An evaluation function circuit 10 carries out addition processing of particular time intervals based on the cross-correlation function values and then searches for the maximum value to calculate time differences.

Abstract: A sonic device, adapted to be carried by a predatory animal is provided. The device emits a sonic signal either continuously or intermittently with a predetermined interval and duration. The device is controlled by a microprocessor (2) which is programmable to emit appropriate signals. The device may be temporarily deactivated by a location switch (12) when the predatory animal enters a defined location, such as a domestic environment, or by an optical switch when the ambient light intensity falls below a particular threshold level. The device includes a waterproof housing and a battery power source and may also include one or more solar panels.

Abstract: An array through a first to a second side of a three-sided junction, accessed remotely by a single mode fiber transmits a light pulse sequence to the array and receives sound modulated return light signals via the second to a third side of the junction. Within each hydrophone, butt coupled fiber joints form a continuous structure, encapsulated within a compressible plastic tube for mechanical stability. Tube volume expands and contracts linearly with variations in acoustic pressure thereby proportionally modulating the optical path therethrough. Each joint is a partial reflector reflects part of the incident light beam back via the second to third side of the junction to a posthydrophone compensating interferometer which compensates for path difference between equally spaced array joints; From the third side of the junction the reflections from the butt coupled fiber joints pass through a light detector and signal processor.

Abstract: A method and system is provided for automated trading of fixed income securities which enables institutional investors, broker dealers and others, to transact directly and anonymously for the purpose of trading investment grade, high yield corporate bonds, municipal bonds or other fixed income securities. A financial institution acting as a Fixed Income Securities system sponsor can act as counterparty to transactions, from trade execution through settlement, and can also serve as a credit intermediary. Computer systems are utilized in conjunction with an electronic communications network to facilitate such fixed income security trading activities. Software routines can direct a trader to various fixed income securities available according to specific criteria put forth by the trader. Software routines can also provide information and services related to the automated trading of fixed income securities.

Abstract: A signal processor circuit has a phase-locked loop with a low-pass filter for removing phase-modulation components from a clock signal. The processor circuit has an isolated power supply for removing amplitude-modulation components from the same clock signal.

Abstract: A communications system includes a base station operable to communicate with a terminal unit over a wireless interface and a packet network coupled to the base station and operable to communicate with the base station. The communications system also includes a network management system coupled to the packet network. The network management system is operable to generate a management message to manage the base station. The network management system is also operable to transparently communicate the management message to the base station and to transparently receive a response to the management message from the base station.