Abstract: A mount for joining a sensor to a structure includes a housing shell joined to the structure and having an interior volume. First and second fluids are disposed in the housing shell. The sensor can be positioned within the housing shell at the interface between the two fluids. A secondary link can be provided to prevent vibration transmission from the structure to the housing shell. A membrane can be provided to separate the first fluid from the second fluid inside the housing shell. Guy lines can also be used to position the sensor.

Abstract: An apparatus and method is provided that utilizes sonar array discontinuities for increasing the directivity gain of a sonar system by increasing the ratio of trace wavelengths (replicated) to the length of a fixed array aperture. Impedance discontinuities, or blocking masses, are embedded in a matrix material of fixed length to create Bragg scattered longitudinal displacements of a wavelength. The longitudinal displacements are induced by an incident acoustic plane wave. This creates longitudinal replicas of the displacements, shifted in wave number, creating a scaled acoustic trace wavelength. The replicated trace wavelength is sampled and resolved, thereby increasing the directivity gain of a sonar system.

Abstract: Using a mechanical shaker test the shear wavespeed in a plate is estimated by applying a cyclical point force to the plate, measuring normal velocity of waves caused by the force, transforming temporal domain measurements with a Fourier transform into a frequency domain, transforming spatial domain measurements into a {kx,ky} wavevector domain spectra using Fourier transforms, determining propagation wavenumbers for given Lamb waves from peaks within the {kx,ky} spectra, and determining shear wavespeed by applying a Newton-Raphson gradient method using the propagation wavenumbers to Raleigh-Lamb dispersion curve equations.

Abstract: The invention as disclosed is a fiber optic interferometric directional acoustic density sensor that increases the directionality of a vector sensor that is much smaller in size than the wave length of an acoustic wave. This is accomplished through the use of second order directionality by measuring the acoustic fluctuations of fluid density at a point, wherein the acoustic density fluctuations are determined according to the principles of fluid compressibility and conservation of mass using a density fluctuation measuring apparatus that restricts two of the three vector components of the particle velocity of the acoustic wave and that employs a laser interferometer to measure the fluid density fluctuation along the remaining vector component.

Abstract: An acoustic sensing device includes a housing having an internal cavity filled with a vibration decoupling medium. An acoustic window formed of an acoustically transparent material is mounted in the housing. This mounting can be by antivibration mounts to prevent housing noise from affecting the acoustic window. A scanning laser vibrometer is positioned within the housing and directed to detect vibrations of the acoustic window. Antivibration mounts are joined between said scanning laser vibrometer and said housing. In further embodiments, the scanning laser vibrometer detects vibrations at a plurality of locations on the acoustic window forming a virtual array.

Abstract: An acoustic sensing device includes a housing having an internal cavity filled with a vibration decoupling medium. An acoustic window formed of an acoustically transparent material is mounted in the housing. This mounting can be by antivibration mounts to prevent housing noise from affecting the acoustic window. A scanning laser vibrometer is positioned within the housing and directed to detect vibrations of the acoustic window. Antivibration mounts are joined between said scanning laser vibrometer and said housing. In further embodiments, the scanning laser vibrometer detects vibrations at a plurality of locations on the acoustic window forming a virtual array.

Abstract: An apparatus for determining a position includes a source which transmits a signal having a source position and a transmission time coded therein. A sensor having a directional beam pattern is positioned at the location of interest. A signal processor steers the directional beam pattern of the sensor in order to determine the direction to the signal source. A sensor processor uses a clock to find a receipt time of the signal. The transmission time and source position is decoded from the signal. The position of interest is calculated from the receipt time, transmission time, direction, and source position. A method is also provided.

Abstract: An underwater acoustic receiver sensor is disclosed that measure up to seven (7) quantities of acoustic field at a collocated point. The quantities measured by the acoustic receiver sensor are acoustic pressure, three orthogonal components of acoustic particle acceleration and three spatial gradients of the acceleration vector. These quantities are appropriately combined and provides for improved directivity of the acoustic receiver sensor.

Abstract: An acoustic vector sensor for monitoring acoustic energy underwater includes an acoustic sensing tri-axial accelerometer, a body of syntactic foam encasing the accelerometer, a body of viscoelastic rubber encasing the body of syntactic foam, and a rigid plastics coating encasing the body of viscoelastic rubber.

Abstract: A system for the detection of acoustic signals utilizing an array of acoustic sensors coupled to a beamformer which generates a steered acoustic beam using the output from one or more of the acoustic sensors within the array. The acoustic sensors include a multiaxis vector sensor co-located with a scalar acoustic pressure sensor. The beamformer generates a weighted output for each acoustic sensor by combining the weighted output of the scalar pressure sensor with the scalar field generated by forming the inner product of the vector components measured at each sensor location with a vector component weighting vector. The weighted output signals are delayed to synchronize the phase of the weighted output signal to that of a weighted signal at a reference array location. The resulting delayed weighted output signals are then summed.

Abstract: A rib-stiffened sound wave projector plate is disclosed which generates low requency sound waves in a fluid medium when energized and flexed. A flexible sound wave projector plate includes at least first and second parallel, major planar surfaces. The first major planar surface includes at least one set of sound wave projector plate ribs, disposed perpendicular to the first major planar surface. Each set of sound wave projector plate ribs includes at least first and second sound wave projector plate rib set members. Each member of the rib sets are offset or spaced laterally from one another by a first predetermined distance, while the first rib member of each rib set is spaced apart a second predetermined distance which is greater than the first distance between the rib set members. Further, each rib set member has a predetermined height and width which may vary from other rib set members in each rib set.