Hybrid Active Noise Control System Using Segmented Filters
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Solution Overview
Problem
Current active noise cancellation (ANC) technologies face limitations due to high latency, high power consumption, and high computational costs, particularly in digital designs, which affect the performance and efficiency of noise cancellation in varying environments and devices.
Innovation Solution
The implementation of a hybrid ANC system using a wideband noise cancellation filter, a narrowband noise cancellation filter, and a feedback filter, with real-time update of coefficients based on error signals, to minimize latency and improve noise cancellation performance across different environments and devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital ANC designs use advanced algorithms with fast digital processing circuits, then noise cancellation performance is improved, but power consumption and computational cost increase
Solution Approach 1:
The patent segments the ANC system into two distinct paths: feedforward path using reference sensor for wideband noise cancellation, and feedback path using error sensor for narrowband noise cancellation. This segmentation allows each path to use optimized processing - feedforward uses simpler processing for wideband signals while feedback uses more advanced adaptive algorithms (like NLMS) specifically for tonal noises, reducing overall computational burden and power consumption while maintaining high noise cancellation performance.
2Reliability
If digital ANC designs use advanced algorithms with fast digital processing circuits, then noise cancellation performance is improved, but computational cost increases
Solution Approach 1:
The patent divides the noise cancellation task into two segments: wideband noise handled by feedforward ANC with reference sensor, and narrowband/tonal noise handled by feedback ANC with error sensor. This segmentation reduces computational cost by assigning appropriate complexity to each segment - feedforward uses less computationally intensive processing for wideband signals, while feedback uses adaptive algorithms (NLMS, FxLMS) only where needed for tonal components, avoiding unnecessary computational overhead across the entire frequency spectrum.
Solution Approach 2:
The patent implements dynamic adaptation of filter coefficients in the feedback path using adaptive algorithms (NLMS, FxLMS) that automatically adjust to changing acoustic environments and device variations. This dynamic approach allows the system to maintain high noise cancellation performance without requiring overly complex fixed-filter designs, as the filters adapt their parameters in real-time based on actual noise conditions and device-specific acoustic characteristics.
3Reliability
If hybrid ANC optimizes both wideband and narrowband noise cancellation, then overall noise cancellation performance is improved, but system complexity increases
Solution Approach 1:
The patent implements a segmented hybrid ANC architecture where feedforward path (reference sensor) handles wideband noise cancellation and feedback path (error sensor) handles narrowband and tonal noise cancellation. This segmentation allows independent optimization of each path - feedforward uses simpler filtering for wideband signals while feedback employs adaptive algorithms for tonal components, achieving comprehensive noise cancellation without requiring both paths to use complex algorithms simultaneously, thus managing system complexity effectively.
4Adaptability or versatility
If RC circuit parameters are changed in real-time to adapt to varying environments, then adaptability is improved, but ease of manufacture worsens due to requiring different component values for each device
Solution Approach 1:
The patent replaces the analog RC circuit approach with a digital signal processing implementation. Instead of physically changing resistor and capacitor values to adapt to different devices and environments, the system uses digital filters with programmable coefficients that can be adjusted via software. This substitution maintains adaptability to varying acoustic environments and device characteristics while dramatically simplifying manufacturing, as all devices use identical hardware that can be configured through digital parameter settings rather than requiring custom analog component values for each unit.
Data Source
AI summary
An apparatus for canceling noise at an ear speaker includes a wideband active noise cancellation filter having a first bandwidth and configured to generate a wideband anti-noise signal from a received reference noise signal, a narrowband active noise cancellation filter having a second bandwidth smaller than the first bandwidth and configured to generate a narrowband anti-noise signal from an error noise signal, a filter between the ear speaker and an error microphone and configured to generate a feedback noise signal, and a controller. The controller is configured to eliminate the error noise signal by modifying coefficients of the wideband active noise cancellation filter and the narrowband active noise cancellation filter in response to the wideband anti-noise signal, the narrowband anti-noise signal, and the feedback noise signal.