Abstract: A method of acoustic depth determination in shallow water. At least one standard acoustic sensor located below an ocean thermocline is provided. The at least one acoustic sensor operates at a first frequency regime and at a second frequency regime. The first frequency regime is above a cut-off frequency. The second frequency regime is below the cut-off frequency. Acoustic data from a moving broadband noise source is recorded at the at least one acoustic sensor. A plot of acoustic intensity as a function of frequency versus time is generated from the acoustic data. A first waveguide invariant density distribution for the first frequency regime and a second waveguide-invariant density distribution for the second frequency regime is generated from the plot using curve detection. Whether the noise source is located below the thermocline is classified based on the first and second waveguide-invariant density distributions.

Abstract: A method of acoustic depth determination in shallow water. At least one standard acoustic sensor located below an ocean thermocline is provided. The at least one acoustic sensor operates at a first frequency regime and at a second frequency regime. The first frequency regime is above a cut-off frequency. The second frequency regime is below the cut-off frequency. Acoustic data from a moving broadband noise source is recorded at the at least one acoustic sensor. A plot of acoustic intensity as a function of frequency versus time is generated from the acoustic data. A first waveguide invariant density distribution for the first frequency regime and a second waveguide-invariant density distribution for the second frequency regime is generated from the plot using curve detection. Whether the noise source is located below the thermocline is classified based on the first and second waveguide-invariant density distributions.

Abstract: A system and method are described for locating and communicating with miners in an underground mine, in which miners carry a battery-powered signal unit with an impact actuator engagable with a wall, floor, or ceiling surface of the mine to transmit acoustic signals through the ground, and actuate controls on the unit to send a predefined message or a specific message via the impact actuator to ground-coupled acoustic receivers coupled with a base station that includes a decoder to determine the message sent by the miner and a location component to determine the miner's location based on the received signals.

Abstract: A system and method are described for locating and communicating with miners in an underground mine, in which miners carry a battery-powered signal unit with an impact actuator engagable with a wall, floor, or ceiling surface of the mine to transmit acoustic signals through the ground, and actuate controls on the unit to send a predefined message or a specific message via the impact actuator to ground-coupled acoustic receivers coupled with a base station that includes a decoder to determine the message sent by the miner and a location component to determine the miner's location based on the received signals.

Abstract: An apparatus for range-estimating a noise source including a first passive, vertical hydrophone array of at least two receivers at a first distance from the noise source. The apparatus includes a second passive, vertical hydrophone array of at least two receivers at a second distance from the noise source. The apparatus also includes a processor communicating with the first passive, vertical hydrophone array and the second passive, vertical hydrophone array to determine a ratio of the first distance to the second distance.

Abstract: An apparatus for range-estimating a noise source including a first passive, vertical hydrophone array of at least two receivers at a first distance from the noise source. The apparatus includes a second passive, vertical hydrophone array of at least two receivers at a second distance from the noise source. The apparatus also includes a processor communicating with the first passive, vertical hydrophone array and the second passive, vertical hydrophone array to determine a ratio of the first distance to the second distance.

Abstract: An acoustic classification system in which echoes from sediment-sediment or water-sediment interfaces are compared to model waveforms predicted by Biot's equations for a given set of acoustic material parameters. The selection of parameters are varied until a match occurs, indicating the correct parameters of the reflecting sediments. Preferably, the variation of selected test parameters is conducted by formal search algorithms, such as simulated annealing or genetic algorithms, to increase computational efficiency.

Abstract: A non-destructive method of measuring physical characteristics of sediments to obtain a cross-sectional distribution of porosity and permeability values and variations, and of shear modulus and shear strength. A pair of boreholes have borehole entries spaced apart from each other at a predetermined distance, and a plurality of hydrophones are spaced at predetermined known positions. A source of seismic energy is placed into another borehole and activated to transmit seismic wave energy from the source to the hydrophones. Seismic wave characteristics are measured in a multiplicity of paths extending from the source to the hydrophones, using cross-bore hole tomography.