Nelson Industries, Inc.

Digisonix, Inc.

Mark C Allie

Larry J Eriksson

Steven R Popovich

Richard H Hoops

Trevor A Laak, Jr

Brian M Finn

Cary D Bremigan

Jerry J Trantow

Douglas E Melton

James E Allard

Charles W Brokish

Geoffrey S Bailey

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.

Active adaptive selective control system

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.

System for developing and operating an active sound and vibration

An act control system introduces a control signal put transducer (14) to combine with the system input signal (6) and yield a system output signal (8). An adaptive filter model (40) has an output (46) supplying a correction signal to the output transducer to introduce the control signal. The model has a first error input (44, 232, 248) driven by an error signal from an error transducer (16) to drive the correction signal toward a value matching the system input signal to modify and/or cancel same. The model has a second error input (202, 224, 240, 268, 280) selectively driven by a spectral leak signal (212) to drive the correction signal away from such matching value by driving the correction signal towards zero, to selectively constrain performance of the model in response to a given condition of a given parameter.

Active adaptive control system with spectral leak

An active acoustic system provides attenuation and spectral shaping of an acoustic wave. A phase lock loop (304) phase locks to the input acoustic wave (6) and generates (306) a desired signal or tone (308) in given phase relation therewith. An error signal (44) from an error transducer or microphone (16) is summed (302) with the desired signal (308) and the resultant sum is supplied to the error input (202) of an adaptive filter model (40) which outputs a correction signal (46) to an output transducer or speaker (14) to introduce the canceling and shaping acoustic wave. In other embodiments, various combinations sum the desired signal (308) with the error signal (44), the model output correction signal (46), and the model input signal (42). Speaker and error path compensation (146, 318, 320) and feedback compensation (340) is provided.

Active acoustic attenuation and spectral shaping system

An acoustic system (20) includes a model reference (22) having a selectably programmable response, and an active model (24) including in combination an acoustic path (26) and an adaptive filter (28) such that the combination of the acoustic path (26) and the adaptive filter (28) adaptively models the model reference (22) such that the combined response of the acoustic path (26) and the adaptive filter (28) provides an active model response matching the response of the model reference (22).

Active acoustic control system matching model reference

An active acoustic attenuation system attenuates a correlated input acoustic wave and eliminates the need for an input transducer sensing such wave. An output transducer introduces a canceling acoustic wave to attenuate the input acoustic wave and yield an attenuated output acoustic wave. An error transducer senses the output acoustic wave and provides an error signal. An adaptive filter model has a model input, a model output outputting a correction signal to the output transducer to introduce the canceling acoustic wave and an error input from the error transducer. A summer has a first input from the model output, a second input from the error transducer, and an output outputting a resultant sum to the model input, such that the model input is provided by the sum of the correction signal and the error signal.

Correlated active attenuation system with error and correction signal

An active acoustic attenuation system specifies the error signal (44) to correspondingly specify the output acoustic wave. In the preferred embodiment, the error signal (44) is specified by summing (210) the error signal (44) with a desired signal (204) to provide a specified error signal (206) to the error input (202) of the adaptive filter model (40) such that the model (40) outputs the correction signal (46) to the output transducer (14) to introduce the canceling acoustic wave which specifies the output acoustic wave such that a desired signal is present in the output acoustic wave.

Active attenuation system with specified output acoustic wave

An active acoustic attenuation system (10) is provided with various adaptive filter models (40, 48, 56, 70, 84, 100) enabling communication between persons (26, 30) in spaced zones (12, 16) by selectively cancelling undesired noise and undesired speech, all on an on-line basis without dedicated off-line pretraining and also for both broadband and narrowband noise.

Communication system with active noise cancellation

A method is provided for reducing convergence time of an active acoustic attenuation system upon start-up or upon a given sensed parameter change. The weights of the adaptive filter model coefficient weight vector are started at or changed to values which are closer to the converged value than the initial or present nonconverged value is to the converged value. The filter model converges in a shorter time as the weights change and are updated from their starting or changed value to the converged value.

Active acoustic attenuation system with reduced convergence time

A microphone probe for acoustic measurement in turbulent flow. The probe includes a tube having a closed end facing upstream with respect to the direction of sound propagation and a microphone is located in a downstream end of the tube. At least a portion of the length of the tube is composed of a rigid foraminous material containing a multiplicity of interconnected cells with the average cell size being less than 100 microns. In operation sound pressure fluctuations cause pressure waves to propagate through the cells to the inside of the tube and the sound pressure waves add constructively to create a high pressure sound at the microphone, while turbulent flow pressure fluctuations are essentially averaged out.

Rigid foraminous microphone probe for acoustic measurement in turbulent

An adaptive active acoustic attenuation system is provided with extended frequency range to attenuate undesired noise which was previously filtered out to avoid instability of the adaptive model. The input signal from the input microphone to the model and the error signal from the error microphone to the model are differentially bandpass filtered to provide a narrower frequency range error signal. In one embodiment, the model operates in its stable region to provide accurate well behaved correction signals to the cancelling loudspeaker, while still receiving a low frequency input noise signal from the input microphone including frequencies below such range. Minimum attenuation frequency has been reduced by at least an octave.

Active acoustic attenuation system with differential filtering

A system is provided for increasing the frequency range of an active acoustic attenuation system in a duct without increasing cut-off frequency f.sub.c of the duct or otherwise splitting or partitioning the duct into separate ducts or chambers. The frequency range is increased above f.sub.c to include higher order modes. A plurality of cancelling model sets are provided. Each transverse portion of the acoustic pressure wave has its own set of an adaptive filter model, cancelling speaker, and error microphone. A single input microphone may service all sets.

Active acoustic attenuation system for higher order mode non-uniform

A microphone probe for acoustic measurement in turbulent flow. The probe includes a tube having a closed end facing upstream with respect to the direction of sound propagation, and a microphone is located in the downstream end of the tube. The tube is provided with a plurality of small ports, or alternately a slit, that extend a substantial portion of the length of the tube and an acoustically resistive material is stretched across the ports and clamped to the tube. In one form of the invention, the side edges of the material are connected to rigid bars and the bars are drawn together by a plurality of threaded fasteners to stretch the material over the ports. The threaded adjustment of the fasteners provides a means for varying the acoustical resistance of the material. In a second form of the invention, the bars to which the side edges of the material are attached, are clamped together by spring clips.

Microphone probe for acoustic measurement in turbulent flow

An active acoustic attenuation system is provided that increases dynamic range by adjusting the amplitude of the input signal and the error signal at respective model and error inputs (42, 44) and providing automatic self-calibration. Input and error transducers (10, 16) provide analog input and error signals which are converted by an analog to digital converter (164, 170) to digital input and error signals for input to the model (40). Digital to analog converters (176) have digital inputs from respective digital input and error signals and operate in an analog to analog mode with analog inputs from respective input and error transducers (10, 16) and analog outputs to the analog to digital converter (164, 170). Dynamic range is also increased by adjusting the amplitude of the correction signal to the output transducer (14).

Active attenuation system with increased dynamic range

Acoustic attenuation apparatus (2) is provided for a duct (4) guiding an acoustic wave propagating (6) therethrough. A silencer (8) is provided for passively attenuating the acoustic wave in the duct, and a cancelling speaker (32) is provided within the silencer. The combination provides hybrid active/passive combined attenuation. Various rectangular and circular structures are disclosed, together with multi-path and multi-speaker arrangements.

Growing community of inventors

Oregon, WI, United States of America

Mark C Allie