Vehicle Noise Cancellation with Harmonic Filtering
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Solution Overview
Problem
Current active noise cancellation systems in vehicles face instability and inefficiency when narrowband and broadband cancellation algorithms operate simultaneously, as they attempt to cancel common frequency content with differing propagation paths, leading to instances of instability or boosting, and often operate independently in overlapping frequency regions, which is inefficient and inaccurate.
Innovation Solution
A noise cancellation system with harmonic filtering that includes input sensors for narrowband and broadband signals, a processor to apply adaptive filters and secondary paths to generate antinoise signals, and an adaptive filter to remove harmonic noise from error signals, preventing the broadband algorithm from adapting to harmonic content and ensuring a more stable system with lower computational demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If narrowband and broadband cancellation algorithms operate simultaneously without harmonic filtering, then both narrowband and broadband noise can be addressed, but instability and boosting occur due to overlapping frequency regions with differing propagation paths
Solution Approach 1:
The patent segments the frequency spectrum by applying a harmonic filter to separate narrowband harmonic frequencies from the broadband signal. This segmentation prevents the broadband algorithm from adapting to harmonic content that should be handled exclusively by the narrowband algorithm, thereby resolving the instability caused by overlapping frequency regions while maintaining comprehensive noise cancellation coverage.
2Ease of operation
If narrowband and broadband algorithms operate independently in overlapping frequency regions, then each algorithm can function autonomously, but computational efficiency decreases and accuracy is reduced
Solution Approach 1:
The patent extracts narrowband harmonic content from the broadband reference signal using a harmonic filter before the broadband adaptive algorithm processes the signal. This extraction ensures that the broadband algorithm operates only on truly broadband content, eliminating redundant computational effort on harmonic frequencies and improving overall computational efficiency while maintaining algorithm autonomy.
3Adaptability or versatility
If the broadband algorithm adapts to harmonic content, then it can cancel a broader range of frequencies, but it creates instability and boosting due to conflicting propagation paths
Solution Approach 1:
The patent converts the potentially harmful effect of the broadband algorithm adapting to harmonic content by proactively filtering out the harmonic content before adaptation occurs. The harmonic filter removes narrowband harmonic frequencies from the broadband reference signal, transforming what would be a source of instability into an opportunity for the broadband algorithm to focus exclusively on broadband noise cancellation, thereby improving both stability and accuracy.
Data Source
AI summary
A noise cancellation system with harmonic filtering for a vehicle audio system may include at least one input sensor configured to transmit reference signals, at least one input sensor configured to transmit a narrowband input signal and a broadband input signal, each of the narrowband input signal and broadband input signal including harmonic noise. The system may include a processor being programmed to receive the reference signals, the reference signals including a narrowband reference signal and a broadband reference signal, apply an adaptive filter to each of the reference signals, apply a secondary path to the input signals to generate antinoise signals, sum the antinoise signals broadcast over the secondary path and the primary noise signals to generate an error signal at the output sensor, and apply an adaptive filter to the error signal to remove harmonic noise to prevent cancelation of the harmonic noise.