Active Noise Control With Real-Time Modifier Block

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Solution Overview

Problem

Existing active acoustic control methods face challenges in effectively attenuating narrow-band disturbing noises due to variations in the secondary path transfer, particularly when using feedback algorithms, leading to instability and high computational burdens, especially in real-time applications.

Innovation Solution

The method employs an internal-model and disturbance-observer control law with a modifier block that adapts in real-time to variations in the electroacoustic system, using a nominal model that remains unchanged while the modifier block adjusts, reducing the number of variable coefficients and simplifying calculations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If adaptive control or multi-model control methods are used to handle variations in secondary path transfer, then the system can adapt to configuration changes, but the computational complexity and data processing requirements increase significantly

Engineering Contradiction:

Improveadaptability to secondary path transfer variationsVSAvoidcomputational complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent pre-calculates and stores transfer functions for multiple possible configurations of the electroacoustic system before runtime. When a configuration change is detected, the system simply retrieves the pre-computed transfer function corresponding to that configuration, avoiding the need for real-time calculation. This preliminary preparation significantly reduces computational complexity during actual operation while maintaining full adaptability to configuration variations.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If feedback algorithms are used for narrow-band noise rejection, then the control can be implemented without reference signals, but the system becomes unstable when secondary path transfer varies significantly

Engineering Contradiction:

Improveoperation simplicityVSAvoidcontrol stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent implements dynamic updating of the transfer function model based on detected configuration changes. Instead of using a static transfer function, the system continuously monitors for configuration variations and updates the transfer function to match the current state. This dynamic adaptation maintains control stability even when secondary path transfer varies significantly, while preserving the simplicity of feedback-only operation.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If the model of the electroacoustic system is updated in real-time to track configuration changes, then the control accuracy is maintained, but the calculation volume and processing time increase

Engineering Contradiction:

Improvecontrol accuracyVSAvoidcalculation speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent segments the configuration space into discrete states, each with a pre-computed transfer function. Instead of continuously updating the model, the system identifies which discrete configuration state is currently active and retrieves the corresponding pre-computed transfer function. This segmentation approach maintains control accuracy by ensuring the transfer function always matches the current configuration, while dramatically reducing calculation volume by replacing continuous computation with discrete state recognition and table lookup.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach allows for effective attenuation of narrow-band disturbing noises while minimizing computational complexity, enabling real-time implementation with a single corrector and reduced data and calculation volumes, thus overcoming the limitations of adaptive and multi-model control methods.

Implementation Method 1

at least one counter-noise loudspeaker intended to produce a counter-noise in said space as a function of a loudspeaker control signal U(k)

Methodology Applied

Scientific EffectAcoustic interference: Interference

Implementation Method 2

at least one error microphone intended to measure the sounds in said space and producing a measurement signal Y(k)

Methodology Applied

Scientific EffectAcoustic measurement: Sound

Data Source

PatentUS9613613B2Method for active narrow-band acoustic control with variable transfer function(s), and corresponding system

Publication Date: 2017.04.04 EXAIL

AI summary

An active acoustic control method for attenuating disturbing narrow-band noise with at least one counter-noise loudspeaker and at least one error microphone in a space forming a material electroacoustic system, the method implementing, in a computing element, a control law with an internal model and disturbance observer with a model of the electroacoustic system, previously obtained by an identification method. The current configuration of the electroacoustic system can vary over time, a nominal configuration of the electroacoustic system is previously determined, a corresponding nominal model Mo(q−1) or Mo(k) previously identified, the control law with an internal model and disturbance observer is implemented in real time, a modifier block Δ(q−1) or Δ(k) is applied to and associated with the nominal model, and the nominal model remains the same during the variations of the current configuration of the electroacoustic system, and the modifier block is varied in real time during these variations.