Techniques are disclosed relating to sensors configured to measure acceleration and pressure. In various embodiments, an apparatus includes a first hydrophone sensor having a first piezoelectric material and a first housing structure and a second hydrophone sensor having a second piezoelectric material and a second housing structure. In some embodiments, the apparatus includes a first pair of wires configured to provide a first differential voltage and a second pair of wires configured to provide a second differential voltage. The first pair of wires may be coupled to the first hydrophone sensor and the second pair of wires may be coupled to the second hydrophone sensor. In various embodiments, the apparatus is configured to determine, based on the first and second differential voltages, a pressure and an acceleration experienced by the first and second hydrophone sensors.

Techniques are disclosed relating to calibrating sensors configured to measure both pressure and acceleration. In various embodiments, a system detects a first voltage produce by a first piezoelectric material in a hydrophone when the hydrophone is exposed to an acceleration and detects a second voltage produced by a second piezoelectric material in the hydrophone when the hydrophone is exposed to the acceleration. The system, in some embodiments, compares the first voltage and the second voltage. Based on the comparing of the first and second voltages, in some embodiments, the system determines a resistance for a variable resistor coupled to one of the first and second piezoelectric materials.

An optical pressure sensor device (1) comprises: a chamber (2) filled with pressure transfer medium and having at least one window (4) transparent to pressure waves; an optical fiber (7) with a Fiber Bragg Grating (8); a first pressure-sensitive mounting assembly (100) arranged within the chamber, holding the optical fiber; a second pressure-sensitive mounting assembly (200) arranged within the chamber, holding the optical fiber. The first pressure-sensitive mounting assembly, the second pressure-sensitive mounting assembly, and a static pressure compensation assembly (300) comprise pairs of bellows arranged on opposite sides of the fiber (7). The bellows (310, 320) of the static pressure compensation assembly have their interior in fluid communication with the pressure transfer medium in the chamber via a choke channel (314, 324), and have very low static stiffness.

A method of modeling an aquatic environment or locating an acoustic source in the aquatic environment. A range-dependent medium is approximated in terms of a series of range-independent regions and obtaining single-scattering solutions across the vertical interfaces between regions. One or more acoustic waves are propagated from a known acoustic source through the range-dependent medium to one or more known seismoacoustic receivers to model iteratively the various solid and liquid layers of the range-dependent medium. Alternatively, one or more acoustic waves are reverse-propagated from one or more known seismoacoustic receivers through the range-dependent medium to determine whether an acoustic source is present within a user-defined range.

A method of modeling an aquatic environment or locating an acoustic source in the aquatic environment. A range-dependent medium is approximated in terms of a series of range-independent regions and obtaining single-scattering solutions across the vertical interfaces between regions. One or more acoustic waves are propagated from a known acoustic source through the range-dependent medium to one or more known seismoacoustic receivers to model iteratively the various solid and liquid layers of the range-dependent medium. Alternatively, one or more acoustic waves are reverse-propagated from one or more known seismoacoustic receivers through the range-dependent medium to determine whether an acoustic source is present within a user-defined range.

A device for receiving acoustic waves, includes an acoustic antenna able to function as a condenser microphone distributed along a line of the acoustic antenna comprising a conductor and a dielectric, the line being a transmission line or being configured to function as a transmission line when the dielectric makes direct physical contact with another conductor, an exciter configured to apply, in a receiving step, an input voltage to a first longitudinal end of the line so as to generate an input electromagnetic wave that moves toward a second longitudinal end of the line and so as to generate an output electromagnetic wave that moves in the opposite direction to the input electromagnetic wave, the input voltage simultaneously comprising a set of sinusoidal voltages comprising a fundamental sinusoidal voltage and a set of harmonics of the fundamental sinusoidal voltage, the frequency of the fundamental sinusoidal voltage being defined so that stationary waves are established in the line such that the output electromagnetic wave comprises directional acoustic-antenna channels.

An autonomous underwater vehicle (1) has a housing (10) having a measurement system (13) with three acceleration or speed sensors on different axes from one another, and a processing unit configured to generate seismic data from the received seismic waves (S1) and to determine the direction (D2) of the acoustic waves (S2) transmitted by an acoustic transmitter (20) from a base (2) which are received by at least two sensors of the measurement system (13). The processing unit generates and transmits, to the navigation system (12), guidance data relating to the determined direction (D2) of the received acoustic waves (S2). The navigation system (12) is configured to control the propulsion and steering system (11) of the vehicle according to the guidance data in order to guide the movement of the vehicle towards the base.

Aspects of the subject technology relate to systems, methods, and computer readable media for estimating acoustic spectra. Acoustic data can be received at a hydrophone array from a first acoustic source and a second acoustic source in a downhole environment. An initial noise spatial correlation matrix estimation can be generated based on the acoustic data. The initial noise spatial correlation matrix estimation can be applied to a beamformer to generate a first source spectra estimation for the first acoustic source and the second acoustic source. A revised noise spatial correlation matrix estimation can be generated based on the first source spectra estimation. The revised noise spatial correlation matrix estimation can be applied to the beamformer to generate a second source spectra estimation for the first acoustic source and the second acoustic source in the downhole environment based on the first source spectra estimation.