A downhole acoustic measurement tool that includes a transducer operable for emitting and/or receiving acoustic signals to perform downhole measurements. The transducer includes multiple piezoelectric elements. Each piezoelectric element may have a first axial end and a second axial end, and the second axial end may be wider than the first axial end in a direction along a circumference of the transducer. The piezoelectric elements may be irregularly pitched azimuthally around one or more portions of a circumference of the transducer. The piezoelectric elements may be spaced apart by no more than the distance defined by W1*f1/F.sub.UL, where F.sub.UL is the upper limit of the frequency band of interest, W1 is the width of the transducer interelement spacing that produces parasitic mode at frequency f1.

An apparatus includes a marine seismic source having a volume of gas and a gas reservoir, and the marine seismic source and the gas reservoir are coupled to permit a resonating gas flow to pass therebetween. The apparatus may be a component of a marine seismic survey system. The apparatus may be utilized in a method of marine seismic surveying.

In accordance with some embodiments of the present disclosure, a method of vibration control for a wellbore logging tool is disclosed. The wellbore logging tool includes an acoustic transmitter. The method may include providing a braking signal to the acoustic transmitter. The braking signal may be based, at least in part, on at least one prior vibration in the acoustic transmitter. The method may include determining a present vibration in the acoustic transmitter after the braking signal has been provided to the acoustic transmitter. The method may include determining whether to update the braking signal and, if so, updating the braking signal based, at least in part, on the present vibration in the acoustic transmitter.

An apparatus is disclosed which may include a plurality of marine seismic sources. According to some embodiments, these marine seismic sources may include a plurality of piezoelectric components. Such an apparatus may provide a useful sound pressure level for conducting marine seismic surveying. According to some embodiments, a conduit may be coupled between the plurality of marine seismic sources and a gas reservoir external to the plurality of marine seismic sources. The conduit may in some embodiments have at least one adjustable dimension for changing a frequency of the apparatus. The apparatus may be used in a method of marine seismic surveying.

A system may include a conduit coupled between a marine seismic source and a gas reservoir external to the seismic source. The conduit may have at least one adjustable dimension for changing a resonance frequency of the system. The system may be utilized in a method of marine seismic surveying.

Embodiments relate to marine acoustic vibrators that incorporate one or more piston plates that act on the surrounding water to produce acoustic energy. An example marine acoustic vibratory may comprise: a containment housing; a piston plate; a fixture coupled to the containment housing; a spring element coupled to the piston plate and the fixture; and a driver coupled to the piston plate and the fixture and configured to move the piston plate back and forth.

This disclosure is related to marine seismic sources, for example marine seismic sources known in the art as benders. Some embodiments of this disclosure use magnetic reluctance forces to produce seismic energy. For example, pole pieces may be attached to one or more plates of a marine seismic source, and a wire coil may induce an attractive force between the pole pieces to cause deformation of the plates to produce seismic energy. Such marine seismic sources may be components of a marine seismic survey system, and may be used in a method of marine seismic surveying. Methods of making marine seismic sources are also disclosed.

The resonant frequency of an example transducer can be adjusted by changing the effective mass of a backing mass using a tuning module. The tuning module includes a electrical source, a switch, and an electromagnetic coil connected in series as an electrical circuit. The electromagnetic coil is mechanically attached to the backing mass, and is disposed within a reservoir of a magneto-rheological fluid enclosed within a casing. When the switch is closed, the electrical source applies a voltage and current to the electromagnetic coil, and induces a localized magnetic field within the magneto-rheological fluid. In response to this localized magnetic field, the magneto-rheological fluid increases in viscosity, assumes properties comparable to a viscoelastic solid, and become affixed to the electromagnetic coil. As the electromagnetic coil is mechanically attached to the backing mass, the solidified magneto-rheological fluid increases the effective mass of the backing mass. As a result, the resonant frequency of the transducer is altered.

Systems, methods, and apparatus to drive reactive loads are disclosed. An example apparatus to drive a reactive load includes a reactive component in circuit with the reactive load, a first switching element in circuit with the reactive load to selectively hold the reactive load in a first energy state and to selectively allow the reactive load to change from the first energy state to a second energy state, a second switching element in circuit with the reactive load to selectively hold the reactive load in the second energy state and to selectively allow the reactive load to change from the second energy state to the first energy state, and a controller to detect a current in the reactive load, and to control the first and second switching elements to hold the reactive load in the first or the second energy state when the current traverses a threshold.

Systems and methods for a sea-floor seismic source are provided. The seismic source system includes a housing (102) having an internal cavity (104). The housing is configured to be coupled to a surface by gravity. The system further includes a coupling plate (106) fixed to a base (108) of the internal cavity. The coupling plate is configured to transmit energy through the base of the internal cavity and into the surface. The system also includes an excitation source (110) located in the internal cavity. The excitation source is configured to receive an input signal from a computing system communicatively coupled to the excitation source, and transmit energy to a reactive mass (112) located in the internal cavity and transmit energy to the coupling plate.