Abstract: In at least one embodiment, an audio amplifier system is provided. The system includes a loudspeaker and an audio amplifier. The loudspeaker transmits an audio output into a listening environment. The audio amplifier is programmed to receive an audio input signal and to generate an excursion signal corresponding to a first excursion level of the voice coil based on the audio input signal. The audio amplifier is further programmed to limit the excursion signal to reach a maximum excursion level and to determine a target pressure for an enclosure of the loudspeaker based on the maximum excursion level. The audio amplifier is further programmed to generate a target current signal based at least on the target pressure and to convert the target current signal into a target voltage signal to a target driving signal to drive the voice coil to reach the maximum excursion level.

Abstract: In at least one embodiment, an audio amplifier system is provided. The system includes a loudspeaker and an audio amplifier. The loudspeaker transmits an audio output into a listening environment. The audio amplifier is programmed to receive an audio input signal and to generate an excursion signal corresponding to a first excursion level of the voice coil based on the audio input signal. The audio amplifier is further programmed to limit the excursion signal to reach a maximum excursion level and to determine a target pressure for an enclosure of the loudspeaker based on the maximum excursion level. The audio amplifier is further programmed to generate a target current signal based at least on the target pressure and to convert the target current signal into a target voltage signal to a target driving signal to drive the voice coil to reach the maximum excursion level.

Abstract: In at least one embodiment, an audio system for extracting online parameters is provided. The system includes a loudspeaker and at least controller. The loudspeaker transmits an audio signal in a listening environment. The at least one controller includes a signal processing block and an adaptive filter. The signal processing block is programmed to provide a driving signal u(n) to drive the loudspeaker to transmit the audio signal. The adaptive filter is programmed to receive the driving signal and to receive a first varying signal i(n) from the loudspeaker in response to the loudspeaker transmitting audio signal. The adaptive filter is further programmed to generate an admittance curve for the loudspeaker based at least on the driving signal and the first varying signal.

Abstract: In at least one embodiment, an audio amplifier system is provided. The system includes a loudspeaker and an audio amplifier. The loudspeaker transmits an audio output into a listening environment. The audio amplifier is programmed to receive an audio input signal and to generate an excursion signal corresponding to a first excursion level of the voice coil based on the audio input signal. The audio amplifier is further programmed to limit the excursion signal to reach a maximum excursion level and to determine a target pressure for an enclosure of the loudspeaker based on the maximum excursion level. The audio amplifier is further programmed to generate a target current signal based at least on the target pressure and to convert the target current signal into a target voltage signal to a target driving signal to drive the voice coil to reach the maximum excursion level.

Abstract: In at least one embodiment, an audio system for extracting online parameters is provided. The system includes a loudspeaker and at least controller. The loudspeaker transmits an audio signal in a listening environment. The at least one controller includes a signal processing block and an adaptive filter. The signal processing block is programmed to provide a driving signal u(n) to drive the loudspeaker to transmit the audio signal. The adaptive filter is programmed to receive the driving signal and to receive a first varying signal i(n) from the loudspeaker in response to the loudspeaker transmitting audio signal. The adaptive filter is further programmed to generate an admittance curve for the loudspeaker based at least on the driving signal and the first varying signal.

Abstract: In at least one embodiment, an audio amplifier system is provided. The system includes a loudspeaker and an audio amplifier. The loudspeaker transmits an audio output into a listening environment. The audio amplifier is programmed to receive an audio input signal and to generate an excursion signal corresponding to a first excursion level of the voice coil based on the audio input signal. The audio amplifier is further programmed to limit the excursion signal to reach a maximum excursion level and to determine a target pressure for an enclosure of the loudspeaker based on the maximum excursion level. The audio amplifier is further programmed to generate a target current signal based at least on the target pressure and to convert the target current signal into a target voltage signal to a target driving signal to drive the voice coil to reach the maximum excursion level.

Abstract: In at least another embodiment, an audio amplifier system including the memory and the audio amplifier is provided. The audio amplifier includes the memory and is programmed to receive an audio input signal and to generate a target current signal based on the audio input signal and a velocity of a diaphragm of a loudspeaker. The audio amplifier is further programmed to generate a corrected current signal based at least on the target current signal and on a predicted position of a voice coil of the loudspeaker and determine the predicted position of the voice coil of the loudspeaker based on a flux density value. The flux density value corresponds to a product of magnetic flux of an air gap for the voice coil in the loudspeaker and a length of a voice coil wire in the loudspeaker.

Abstract: In at least one embodiment, an audio amplifier system including a memory and an audio amplifier is provided. The audio amplifier includes the memory and is programmed to receive an audio input signal and to generate a target current signal based on the audio input signal. The audio amplifier is further configured to generate a first predicted position of a voice coil of a loudspeaker and to generate a first corrected current signal based on the target current signal and on the first predicted position of the voice coil. The audio amplifier is further configured to determine a pressure within a loudspeaker enclosure based at least on the first predicted position of the voice coil and determine a position of a passive radiator based at least on the pressure within the loudspeaker enclosure. The audio amplifier is further configured to generate a second predicted position of the voice coil.

Abstract: A quadrupole responder for an OQR-type gravity gradiometer comprises a housing, and a mass quadrupole positioned within the housing. The mass quadrupole has a pair of sides, and also has a center of mass between the sides. At least a pair of torsion spring flexures are provided by pins connecting said side of said mass quadrupole to the housing. The torsion spring flexures provide an axis of rotation which passes through the center of mass of the mass quadrupole and through both spring flexures. The pins are integral with the mass quadrupole.

Abstract: Systems and methods for determining a bias-corrected value of at least one component of a gravity gradient tensor using a gravity gradiometer and a measurement bias of the gravity gradiometer wherein the measurement bias varies with time, by taking at least three measurements with the gravity gradiometer positioned in at least two orientations. Any gravity gradiometer can be used, including a Cross-Component Gravity Gradiometer (CCGG), an Orthogonal Quadrupole Responder (OQR), an In-Line Responder (ILR), a Diagonal-Component Gravity Gradiometer, or a Multi-Component Gravity Gradiometer (MCGG).

Abstract: Several push-pull linear hybrid class H amplifiers are disclosed. A split power rail provides a positive supply rail and a negative supply rail in response to a power supply control voltage. A push-pull amplifier stage is powered by the positive and negative supply rails. The amplifier stage receives an input signal and provides a corresponding amplified output signal. A power supply control circuit provides the power supply control voltage in response to the smaller of the positive and negative supply rails, and the input signal.

Abstract: A quadrupole responder for an OQR-type gravity gradiometer comprises a housing, and a mass quadrupole positioned within the housing. The mass quadrupole has a pair of sides, and also has a center of mass between the sides. At least a pair of torsion spring flexures are provided by pins connecting said sideof said mass quadrupole to the housing. The torsion spring flexures provide an axis of rotation which passes through the center of mass of the mass quadrupole and through both spring flexures. The pins are integral with the mass quadrupole.

Abstract: Systems and methods for determining a bias-corrected value of at least one component of a gravity gradient tensor using a gravity gradiometer and a measurement bias of the gravity gradiometer wherein the measurement bias varies with time, by taking at least three measurements with the gravity gradiometer positioned in at least two orientations. Any gravity gradiometer can be used, including a Cross-Component Gravity Gradiometer (CCGG), an Orthogonal Quadrupole Responder (OQR), an In-Line Responder (ILR), a Diagonal-Component Gravity Gradiometer, or a Multi-Component Gravity Gradiometer (MCGG).

Abstract: A quadrupole responder for an OQR-type gravity gradiometer comprises a housing, and a mass quadrupole positioned within the housing. The mass quadrupole has a pair of sides, and also has a center of mass between the sides. At least a pair of torsion spring flexures are provided by pins connecting said side of said mass quadrupole to the housing. The torsion spring flexures provide an axis of rotation which passes through the center of mass of the mass quadrupole and through both spring flexures. The pins are integral with the mass quadrupole.

Abstract: Several push-pull linear hybrid class H amplifiers are disclosed. A split power rail provides a positive supply rail and a negative supply rail in response to a power supply control voltage. A push-pull amplifier stage is powered by the positive and negative supply rails. The amplifier stage receives an input signal and provides a corresponding amplified output signal. A power supply control circuit provides the power supply control voltage in response to the smaller of the positive and negative supply rails, and the input signal.

Abstract: The invention provides a method of locating, in terrain containing oil sand deposits and also containing shale, clean oil sands deposits (i.e. those not containing significant shale) which are large enough for economic exploitation. The method includes flying a high sensitivity gravity gradiometer over the terrain and measuring at least one component, preferably the vertical component, of the local gravity gradient field at a number of points in a grid pattern on the terrain. The densities of sand and shale are normally approximately the same, making it difficult to distinguish them. However in an oil sands environment, there can be a sufficient difference in bulk density such that by using a very sensitive gravity gradiometer, or by otherwise reducing the noise signal using appropriate surveying methods, large clean oil sand deposits can be distinguished from other oil sand deposits not large enough for economic exploitation.

Abstract: A quadrupole responder for an OQR-type gravity gradiometer comprises a housing, and a mass quadrupole positioned within the housing. The mass quadrupole has a pair of sides, and also has a center of mass between the sides. At least a pair of torsion spring flexures are provided by pins connecting said side of said mass quadrupole to the housing. The torsion spring flexures provide an axis of rotation which passes through the center of mass of the mass quadrupole and through both spring flexures. The pins are integral with the mass quadrupole.

Abstract: The invention provides a method of locating, in terrain containing oil sand deposits and also containing shale, clean oil sands deposits (i.e. those not containing significant shale) which are large enough for economic exploitation. The method includes flying a high sensitivity gravity gradiometer over the terrain and measuring at least one component, preferably the vertical component, of the local gravity gradient field at a number of points in a grid pattern on the terrain. The densities of sand and shale are normally approximately the same, making it difficult to distinguish them. However in an oil sands environment, there can be a sufficient difference in bulk density such that by using a very sensitive gravity gradiometer, or by otherwise reducing the noise signal using appropriate surveying methods, large clean oil sand deposits can be distinguished from other oil sand deposits not large enough for economic exploitation.

Abstract: A gravity gradiometer having quadrupole responders in which a mass quadrupole is supported by a torsional spring forming a flexure allowing rotation of the mass quadrupole about its center of mass. The flexure can be a pair of spaced apart posts. The flexure can be made from glassy metal having at room temperature a high elastic limit, high stiffness, high strength and low internal damping. The flexure can alternatively be a web made of glassy metal.

Abstract: A gravity gradiometer is combined with a two-stage actively controlled isolation system. The gravity gradiometer and two stage isolation system may then be mounted within (or on) a mobile vehicle such as, for example, an aircraft. It has been recognized by the inventors herein that the accelerations imparted to an aircraft during normal operations can be separated through system design into two relatively distinct regimes within the frequency domain. The invention provides a first isolation mount, which forms part of the isolation system, to isolate accelerations (and resulting translations) falling within a first of the two frequency regimes. The second isolation mount, which is mounted to the first isolation mount, isolates accelerations falling within the second of the two frequency regimes. A gravity gradiometer can then be mounted to the second isolation mount.