Abstract: Digital filters for processing an input audio signal for extending the audio capabilities and reducing distortion of a loudspeaker. Such extension may include a general sound pressure level (SPL) extension or a more targeted low frequency (LF) extension. This may be accomplished by modifying an original frequency response of the loudspeaker to achieve a particular extension, and applying a digital linear filter based on the modified frequency response to the audio signal. A nonlinear digital filter may also be applied to the audio signal reduce nonlinear distortions of the loudspeaker. The nonlinear digital filter may be based on an inverse of an electro-mechanical model of the loudspeaker. In this manner, a loudspeaker may be driven close to its maximum theoretical power capability without increasing distortion in the loudspeaker output.

Abstract: In one embodiment, a pre-correcting engine generates a pre-corrected signal that may be used to mitigate air path distortions in sounds generated by loudspeaker systems that include loudspeakers coupled to waveguides. In operation, the pre-correcting engine virtually propagates a target signal in a reverse direction from the output of the waveguide to the output of a driver. Notably, the pre-correcting engine implements a propagation distortion compensation model that, when applied to the target signal, corrects for the effects of air path distortions on the target signal. The pre-correcting engine then transmits the pre-corrected signal to the driver. As the driver drives the waveguide based on the pre-corrected signal, effects of the pre-corrected distortions negate effects of air path distortions and the loudspeaker system generates high-fidelity sounds.

Abstract: Technology for blind phase-shift keying (PSK) and quadrature amplitude modulation (QAM) identification of a received radio frequency (RF) signal is disclosed. One method can include: uniform sub-sampling the received RF signal to eliminate a phase contribution from a carrier frequency of the received RF signal; and computing a likelihood function of observed phase differences of the sub-sampled received RF signal of a phase sequence for each PSK modulation type. Another method can include: non-uniformly sub-sampling the received RF signal for a distribution of signal amplitudes of the received RF signal; and computing a likelihood function of the signal amplitudes of the sub-samples of the received RF signal for each modulation type.

Abstract: In one embodiment, a pre-correcting engine generates a pre-corrected signal that may be used to mitigate air path distortions in sounds generated by loudspeaker systems that include loudspeakers coupled to waveguides. In operation, the pre-correcting engine virtually propagates a target signal in a reverse direction from the output of the waveguide to the output of a driver. Notably, the pre-correcting engine implements a propagation distortion compensation model that, when applied to the target signal, corrects for the effects of air path distortions on the target signal. The pre-correcting engine then transmits the pre-corrected signal to the driver. As the driver drives the waveguide based on the pre-corrected signal, effects of the pre-corrected distortions negate effects of air path distortions and the loudspeaker system generates high-fidelity sounds.

Abstract: Technology for blind phase-shift keying (PSK) and quadrature amplitude modulation (QAM) identification of a received radio frequency (RF) signal is disclosed. One method can include: uniform sub-sampling the received RF signal to eliminate a phase contribution from a carrier frequency of the received RF signal; and computing a likelihood function of observed phase differences of the sub-sampled received RF signal of a phase sequence for each PSK modulation type. Another method can include: non-uniformly sub-sampling the received RF signal for a distribution of signal amplitudes of the received RF signal; and computing a likelihood function of the signal amplitudes of the sub-samples of the received RF signal for each modulation type.

Abstract: Technology for blind phase-shift keying (PSK) and quadrature amplitude modulation (QAM) identification of a received radio frequency (RF) signal is disclosed. One method can include: uniform sub-sampling the received RF signal to eliminate a phase contribution from a carrier frequency of the received RF signal; and computing a likelihood function of observed phase differences of the sub-sampled received RF signal of a phase sequence for each PSK modulation type. Another method can include: non-uniformly sub-sampling the received RF signal for a distribution of signal amplitudes of the received RF signal; and computing a likelihood function of the signal amplitudes of the sub-samples of the received RF signal for each modulation type.

Abstract: Digital filters for processing an input audio signal for extending the audio capabilities and reducing distortion of a loudspeaker. Such extension may include a general sound pressure level (SPL) extension or a more targeted low frequency (LF) extension. This may be accomplished by modifying an original frequency response of the loudspeaker to achieve a particular extension, and applying a digital linear filter based on the modified frequency response to the audio signal. A nonlinear digital filter may also be applied to the audio signal reduce nonlinear distortions of the loudspeaker. The nonlinear digital filter may be based on an inverse of an electro-mechanical model of the loudspeaker. In this manner, a loudspeaker may be driven close to its maximum theoretical power capability without increasing distortion in the loudspeaker output.

Abstract: A method and apparatus are present for monitoring a structure. A signal is sent into the structure, wherein the signal has a limited duration and a varying frequency. A response to the signal is received and the response is compared to a baseline to form a comparison.

Abstract: Adaptive notch filters can be used to estimate offending frequencies caused by feedback within a hearing aid system. The offending frequencies can be suppressed by filtering. Offending frequencies can be identified based on variability of the adaptive notch filter parameters.

Abstract: A method is present for mapping changes in a structure. A plurality of responses is collected from a set of transmitter and sensor pairs for the structure. Change metrics for pixels in a plurality of grids are identified from the plurality of responses, wherein a first grid in the plurality of grids is shifted in relation to a second grid in the plurality of grids. A map is generated for the structure using the change metrics.

Abstract: A method is present for monitoring a structure. A plurality of modes is identified for a first response for the structure at a first temperature. Each mode in the plurality of modes is adjusted from the first temperature to the second temperature to form a plurality of temperature adjusted modes. A temperature adjusted response is formed from the plurality of temperature adjusted modes in which the temperature adjusted response is adjusted to a second temperature from the first temperature. The temperature adjusted response is compared to a second response to evaluate the changes in the structure between the two sets of measurements.

Abstract: Adaptive notch filters can be used to estimate offending frequencies caused by feedback within a hearing aid system. The offending frequencies can be suppressed by filtering. Offending frequencies can be identified based on variability of the adaptive notch filter parameters.

Abstract: A method, apparatus, and computer program product for identifying dissimilarity indices for a structure is presented. A first test signal is sent into a baseline model of the structure. An estimated response signal to the first test signal sent into the baseline model of the structure is received. A second test signal is sent into the structure. A second response single to the second test signal is received. A value is assigned to a model-based dissimilarity index using the first response compared to the second response.

Abstract: A method, apparatus, and computer program product for identifying dissimilarity indices for a structure is presented. A first test signal is sent into a baseline model of the structure. An estimated response signal to the first test signal sent into the baseline model of the structure is received. A second test signal is sent into the structure. A second response single to the second test signal is received. A value is assigned to a model-based dissimilarity index using the first response compared to the second response.

Abstract: A method is present for monitoring a structure. A plurality of modes is identified for a first response for the structure at a first temperature. Each mode in the plurality of modes is adjusted from the first temperature to the second temperature to form a plurality of temperature adjusted modes. A temperature adjusted response is formed from the plurality of temperature adjusted modes in which the temperature adjusted response is adjusted to a second temperature from the first temperature. The temperature adjusted response is compared to a second response to evaluate the changes in the structure between the two sets of measurements.

Abstract: A method and apparatus are present for monitoring a structure. A signal is sent into the structure, wherein the signal has a limited duration and a varying frequency. A response to the signal is received and the response is compared to a baseline to form a comparison.

Abstract: A method is present for mapping changes in a structure. A plurality of responses is collected from a set of transmitter and sensor pairs for the structure. Change metrics for pixels in a plurality of grids are identified from the plurality of responses, wherein a first grid in the plurality of grids is shifted in relation to a second grid in the plurality of grids. A map is generated for the structure using the change metrics.

Abstract: A method for diagnosing the health of a transducer may include transmitting a signal to a transducer to cause the transducer to transmit a stress wave into an object being monitored, wherein the signal has a predetermined frequency range or bandwidth. The method may also include receiving response data for the transducer and transforming the response data to data representative of an impedance curve of impedance versus frequency for the predetermined frequency range. The method may further include extracting selected parameters from the impedance curve to diagnose the health of the transducer.

Abstract: A method for diagnosing the health of a transducer may include transmitting a signal to a transducer to cause the transducer to transmit a stress wave into an object being monitored, wherein the signal has a predetermined frequency range or bandwidth. The method may also include receiving response data for the transducer and transforming the response data to data representative of an impedance curve of impedance versus frequency for the predetermined frequency range. The method may further include extracting selected parameters from the impedance curve to diagnose the health of the transducer.

Abstract: An embodiment of a method of predicting maternal hypertension during pregnancy is disclosed. The method may include measuring a maternal blood velocity waveform and measuring a fetal blood velocity waveform. The method may further include the calculation of a coherence value using a magnitude-squared coherence function between the maternal and fetal blood velocity waveforms and comparing the coherence value to a predetermined threshold value.