Active Noise Control with Alternating Adaptive Filters for Ear Position Shift
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Solution Overview
Problem
Existing active noise control systems face challenges in effectively canceling noise when a user's posture changes, leading to diffraction or distance attenuation of noise cancellation sound, which increases processing complexity and load, especially when multiple speakers and microphones are used to accommodate varying ear positions.
Innovation Solution
The system employs two noise control systems with different speaker and microphone configurations, using auxiliary filters to generate correction signals for error signals detected by microphones, and adaptive filters to produce noise cancellation sound, with a control unit managing the adaptive operations to minimize interference and adapt to changing user positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple speakers and microphones are arranged at different positions to accommodate user posture changes, then noise cancellation effectiveness is improved, but device complexity and processing load increase
Solution Approach 1:
The system divides the noise control function into multiple independent noise control lines, each with its own speaker and microphone pair. Each line operates semi-independently with dedicated auxiliary and adaptive filters, allowing the system to handle multiple positions without requiring a fully interconnected complex network of speakers and microphones.
Solution Approach 2:
The control unit alternately performs adaptive operations for different noise control lines in a periodic manner rather than simultaneously. This time-division multiplexing approach allows the system to adapt to multiple positions sequentially, reducing the computational load at any given moment while maintaining effectiveness across different user postures.
2Adaptability or versatility
If multiple speakers and microphones are arranged at different positions to accommodate user posture changes, then noise cancellation effectiveness is improved, but processing load increases
Solution Approach 1:
The system segments the processing tasks by assigning dedicated auxiliary filters and adaptive filters to each noise control line. This segmentation allows parallel processing of different noise control lines during alternate adaptive operations, distributing the processing load across multiple independent filter chains rather than requiring a single complex processing unit.
Solution Approach 2:
The control unit implements periodic alternating execution of adaptive operations across different noise control lines. By switching between lines in time-division fashion rather than processing all simultaneously, the system reduces the peak processing load on the DSP while maintaining adaptability to multiple positions through sequential updates.
3Measurement precision
If transfer function simulation filter is constructed by DSP signal processing, then noise cancellation accuracy is improved, but processing load becomes excessive
Solution Approach 1:
The transfer function simulation is segmented into multiple independent auxiliary filters, each handling a specific noise control line and position. By dividing the overall transfer function simulation into smaller, specialized filter segments, the system achieves accurate noise cancellation for each position while distributing the computational burden across multiple simpler filter operations rather than one complex simultaneous computation.
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 configuration allows for effective noise cancellation with reduced processing complexity, even with changes in user posture, by alternately performing adaptive operations and adjusting step sizes based on detected user positions, ensuring satisfactory noise cancellation across different ear positions.
Implementation Method 1
a speaker that outputs noise cancellation sound... generates noise cancellation sound from the noise signal... to cancel noise heard by a user
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
To provide an "active noise control system" capable of satisfactorily canceling noise even when a position of an ear fluctuates. Adaptive operations of a first noise control system (1) and a second noise control system (2) including a speaker that outputs noise cancellation sound, a microphone that detects an error signal, an auxiliary filter that generates, from a noise signal, a correction signal that corrects the error signal so that a difference in a position between the microphone and a noise cancellation position is compensated, and an adaptive filter that performs an adaptive operation using the corrected error signal to generate the noise cancellation sound from the noise signal are alternately performed. A transfer function learned in a state in which the second noise control system (2) is stopped is set in the auxiliary filter of the first noise control system (1), and a transfer function learned in a state in which the adaptive operation of the first noise control system (1) is stopped is set in the auxiliary filter of the second noise control system (2).