Adaptive Digital Filter for Active Noise Cancellation
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Solution Overview
Problem
Existing active noise cancellation (ANC) systems face challenges in efficiently adapting to changing ambient noise conditions and achieving optimal noise reduction across a range of frequencies, particularly in applications like headphones and communications devices, where background noise interference is significant.
Innovation Solution
The implementation of a digital filter with adaptive states, where the filter state transitions between two distinct states based on information from both the reference noise signal and an error signal, allowing for real-time adjustments in the filtering process to optimize noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed filter state is used in ANC systems, then device complexity is reduced, but adaptability to changing ambient noise conditions deteriorates
Solution Approach 1:
The patent implements a digital filter with two distinct states (first filter state and second filter state) that can transition between them based on noise conditions. The adaptation domain calculates filter states dynamically using reference noise signals and error signals, allowing the system to adapt to changing ambient noise while maintaining manageable complexity through structured state transitions.
Solution Approach 2:
The system changes filter parameters by switching between different filter states. The first filter state and second filter state represent different parameter configurations that are selected based on the calculated adaptation needs, allowing the system to optimize performance for different noise conditions without requiring continuous complex adjustments.
2Reliability
If adaptive filter states are implemented, then noise cancellation performance is improved, but computational complexity increases
Solution Approach 1:
The adaptation domain uses feedback from both the reference noise signal and the error signal to calculate the appropriate filter state. This feedback mechanism allows the system to automatically adjust and optimize noise cancellation performance based on real-time conditions, improving reliability while keeping the adaptation process systematic and manageable.
Solution Approach 2:
The system pre-calculates and maintains two distinct filter states in advance. Rather than computing complex adaptations in real-time during noise cancellation, the system prepares the filter states beforehand and selects between them based on current conditions, reducing real-time computational complexity while maintaining high performance.
3Reliability
If real-time filter adaptation is performed, then noise reduction efficacy across frequencies is improved, but processing time increases
Solution Approach 1:
The system performs filter adaptation periodically by transitioning between two distinct filter states rather than continuously adjusting parameters. This periodic action allows the adaptation domain to calculate and switch filter states at optimized intervals, maintaining noise reduction efficacy across frequencies while minimizing the time lost to adaptation processes.
Data Source
AI summary
An adaptive active noise cancellation apparatus performs a filtering operation in a first digital domain and performs adaptation of the filtering operation in a second digital domain.