Abstract: A digital voice enhancement, DVE, communication system includes an instability detector detecting an unstable acoustic feedback condition from a loudspeaker to a microphone by sensing a condition of the electrical signal transmitted from the microphone to the loudspeaker, and a corrective processor responsive to the instability detector to modify the electrical signal to reduce unstable acoustic feedback. The sensed condition may be magnitude, power, or, preferably, the sinusoidal characteristic of the electrical signal, namely the electrical signal becoming sinusoidal in nature.

Abstract: A digital voice enhancement, DVE, communication system includes a dynamic range processor and method altering dynamic range of the electrical signal from the microphone to the loudspeaker by applying nonlinear and/or differential gain thereto, preferably applied by a slope intercept formula.

Abstract: In a DVE, digital voice enhancement, communication system, the selection decision for choosing which microphone to be active is based on a given function of the speech of a respective talker relative to his/her acoustic environment at the respective microphone. The selection decision is based on a selection technique normalizing at least one of a) different microphone sensitivities and b) different background noise levels at the respective microphones, preferably based on the ratio of how much louder a talker speaks over the background noise at his/her respective microphone.

Abstract: An integrated vehicle voice enhancement system and hands-free cellular telephone system implements microphone steering techniques and noise reduction filtering to improve the intelligibility and clarity of transmitted signals. A microphone steering switch is provided for the cellular telephone interface which allows only one of the microphones to be switched in to an “on” state at any given time. The microphone steering switch generates a raw telephone input switch that is a combination of 100% of the designated primary microphone signal and approximately 20% of the microphone signals from microphones in the “off” state. In this manner, the telephone line does not appear dead to a listener on the other end of the telephone line when speech is not present in the telephone input signal. A noise reduction filter filters the raw telephone signal in the time domain in real time to improve the clarity of the telephone input signal when speech is present in the telephone input signal.

Abstract: Full acoustic coupling and echo cancellation is provided in implementations where there is acoustic coupling between acoustic zones.

Abstract: A digital voice enhancement communication system, including a simplex system, has first and second acoustic zones, and respective microphones and loudspeakers. A voice sensitive gated switch has a first mode supplying the output of a first microphone in the first zone over a first channel to a second loudspeaker in the second zone, and has a second mode supplying the output of a second microphone in the second zone over a second channel to the first loudspeaker in the first zone. First and second noise sensitive bandpass filters and first and second equalization filters are provided in the first and second channels, respectively. Each noise sensitive bandpass filter is a noise responsive highpass filter having a filter cutoff effective at elevated noise levels and reducing bandwidth and making more gain available, to improve intelligibility of speech of a person in the respective zone transmitted from the respective microphone to the loudspeaker in the other zone.

Abstract: An adaptive passive acoustic attenuation system implements control techniques to facilitate practical use of adaptive passive acoustic attenuation in industrial and commercial applications. The system includes multiple banks of multiple adjustable tuners that are used to passively attenuate an acoustic disturbance (e.g. a tone) propagating through an acoustic plant. All of the tuners in one of the banks are contemporaneously adjusted during an adaptation scan while the tuners in the other banks remain stationary. The process is then carried out for the other banks of adjustable tuners. The number of adjustable tuners per bank is chosen so that adaptation scans of the tuners in the respective bank create observable changes in acoustic levels to enable adaptation. Multiple sets of multiple banks of adjustable tuners can be provided to attenuate multiple disturbances propagating through the acoustic plant.

Abstract: An adaptive control system implements a back-projection technique to limit adaptation of adaptive parameters in the system so that system actuators are not driven beyond desired physical limitations. When the optimal controller solution lies outside of a desired region in the parameter space, chosen in accordance with the physical limitations of the system, adaptation is back-projected onto or near a smooth convex surface defining the edge of the desired region. Adaptation is preferably normalized to improve adaptation convergence. Back-projection is preferably compensated in accordance with adaptation normalization to facilitate convergence. To lessen computational burdens, adaptation and/or back-projection is accomplished in accordance with a time-sharing technique in which orthogonal components are separately processed. The technique can be implemented in tonal control systems, and in systems capable of controlling non-periodic disturbances.

Abstract: An adaptive acoustic attenuation system has distributed nodal processing and a shared state nodal architecture. The system includes a plurality of adaptive filter nodes, each preferably having a dedicated digital signal processor. Each adaptive filter node preferably receives a reference signal and generates a correction signal that drives an acoustic actuator. Each adaptive filter node also shares nodal state vectors with adjacent adaptive filter nodes. The calculation of the nodal correction signals depends both on the reference signal and nodal state vectors received from adjacent adaptive filter nodes. The calculation of nodal state vectors shared with adjacent adaptive filter nodes depends on nodal state vectors received from other adjacent adaptive filter nodes as well as nodal reference signals inputting the adaptive filter node.

Abstract: An active adaptive control system introduces a control signal from an output transducer (14) to combine with the system input signal (6) and yield a system output signal (8). An error transducer (16) senses the system output signal and provides an error signal (44). An adaptive filter model (40) has a model input from a reference signal (42) correlated to the system input signal, and an output outputting a correction signal (46) to the output transducer to introduce the control signal. Performance of the model is selectively controlled to control the signal sent to the output transducer. Various monitoring and control methods are provided, including spectral leak signal monitoring and control, correction signal monitoring and control, frequency responsive spectral transfer function processing of the leak signal and/or the correction signal, reference signal processing, and fuzzy logic control.

Abstract: An active adaptive control system and method has frequency dependent filtering with a transfer characteristic which is a function of a frequency dependent shaped power limitation characteristic maximizing usage of available output transducer authority. Band separation is provided for different tones. Power limit partitioning is provided for effectively distributing power between correction tones to maximize model performance.

Abstract: Robust acoustic echo cancellation in a single-channel integrated audio and intercom system is provided by adapting echo cancellation filters in accordance with an optimized autocorrelation matrix. This is carried out in a modified FIR LMS filter in which the adaptation regressor signal is formed by a combination of one or more of the received voice signal, the received audio signal, and/or a random noise signal. In a SISO system, it is usually desirable to shelter the regressor signal from tonal components such as voice signals. In a multiple-channel system, it is usually desirable to shelter regressor signals for a particular channel from acoustic components that are likely to be correlated to acoustic components in other parts of the system and are likely to affect that particular channel. In multi-channel applications, it is therefore usually desirable to shelter regressor signals from audio signals.

Abstract: An active acoustic attenuation system in which the region of desired acoustic control is remote from an error sensor. The invention uses an adjusted error signal from the remote error sensor to update an adaptive control filter. The adaptive control filter drives an output transducer which outputs a secondary input that destructively interferes with and cancels an acoustic disturbance. Adaptation of the adaptive control filter compensates for the error sensor being remote from the region of desired control by adjusting the error signal in accordance with an H filter representing a relationship between a disturbance signal measured by the error sensor and a disturbance signal as would be measured in the region of desired control. The invention includes feedforward and regenerative feedback embodiments, as well as SISO and MIMO embodiments.

Abstract: An active silencer for a vehicle exhaust system that is constructed so that it can be hung underneath the vehicle without altering the vehicle. The silencer has a chamber isolated from the exhaust flow. A duct spans longitudinally through the chamber. One or more loudspeakers (e.g. 2 or 4 loudspeakers) are mounted on the duct side-by-side. The loudspeakers share a common tuning volume within the duct which is ported to a mixing apparatus where the canceling acoustic wave mixes with noise from the exhaust flow before the exhaust noise exits to the atmosphere.

Abstract: Coherence optimization is provided in an active adaptive control system. The adaptive control model (16) has a model input (18) receiving a reference signal (8) from a reference input transducer (4), an error input (20) receiving an error signal (14) from an error transducer (10), and a model output (22) outputting a correction signal (24) to an output transducer (26) to introduce a control signal matching the system input signal (6) to minimize the error at the error input. Coherence in the system is determined, and a coherence filter (27; 28; 29) is provided according to the determined coherence. Preferably, one or more of the error signal (14), reference signal (8) and correction signal (24) is coherence filtered.

Abstract: An adaptive control system and method for actively canceling tones in an active acoustic attenuation system has an adaptive parameter bank. Adaptation of the adaptive parameter bank can be constrained with respect to the null space of a C model of an auxiliary path (e.g. speaker-error). Alternatively, output from the adaptive parameter bank can be constrained with respect to the effective null space of the C model. The preferred system uses singular value decomposition, normalization, and demodulation to implement the methods of constraining output and adaptation. The invention can eliminate stability and tracking problems associated with over-parameterization.

Abstract: A system that facilitates the development and operation of active sound or vibration control systems, especially for those not skilled in computer programming. The system facilitates the development of developing active sound or vibration control systems implementing an adaptive control model. In particular, the system has a software collection containing control system software that implements an adaptive control model which can be programmed on an electronic controller to actively control sound or vibration. The system also has a user interface that prompts the user to enter information pertaining to the control system being developed so that the electronic controller can implement an adaptive control model in accordance with the information entered by the user.

Abstract: In an active adaptive attenuation system having a main model, a second adaptive filter model is provided having an input from the output of the main model, and an output supplied to the input of the main model. A copy of the main model has an input from the input to the second model and an output supplied to a multiplier multiplying the error signal and the output of the copy and supplying the resultant product as a weight update signal to the second model.

Abstract: A multi-channel communication system is provided. In an active acoustic attenuation implementation, noise, including cross-coupled noise between channels and locations, designated audio signals, and echoes, are canceled, but not speech from another location. A particularly desirable vehicle application is provided.

Abstract: An active control system having an adaptive filter model in which the effect of transfer functions after the adaptive filter model output are eliminated from the adaption process. The adaptive control scheme inputs a reference signal to a copy of the adaptive filter model, and the copy of the adaptive filter model outputs a correction signal that drives an output transducer. The copy of the adaptive filter model does not receive an error input signal. Adaption occurs in the adaptive filter model. The model input to the adaptive filter model is a C-filtered reference signal. There are no transfer functions between the output of the adaptive filter model and the error input to the adaptive filter model. The error input to the adaptive filter model is a combination of an error signal from an error sensor, a C-filtered correction signal, and a model output signal from the adaptive filter model.