Frequency-Domain ANC Leakage Control for Stable Vehicle Noise Cancellation
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Solution Overview
Problem
Existing active noise cancellation (ANC) and road noise cancellation (RNC) systems rely on time domain-based limiters that are ineffective for detecting excessive abnormal inputs from various vehicles and roads, leading to impractical and unstable noise cancellation performance.
Innovation Solution
A system and method for frequency dependent dynamic leakage (FDDL-X) that monitors input signals in the frequency domain, using a current limiter to convert reference signals from time to frequency domain, apply gain constants, and compare against frequency domain thresholds to dynamically adjust leakage gains, ensuring balanced input signals and stable noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time domain-based limiters are used in ANC/RNC systems, then the system structure is simple, but the system cannot effectively detect excessive abnormal inputs from various vehicles and roads, leading to unstable noise cancellation performance
Solution Approach 1:
The patent transforms the reference signal from time domain to frequency domain using FFT, and changes the limiting operation from time-domain amplitude limiting to frequency-domain magnitude limiting. This parameter transformation enables effective detection of excessive inputs while maintaining system stability. The frequency domain representation allows for frequency-dependent leakage adjustment, which resolves the contradiction between reliability and complexity.
Solution Approach 2:
The patent replaces the traditional time-domain mechanical limiting mechanism with a frequency-domain computational approach. Instead of using simple amplitude clipping in time domain, the system uses frequency domain transformation and complex number operations to achieve more sophisticated signal control, improving reliability while managing complexity through algorithmic substitution.
2Reliability
If frequency domain monitoring is implemented to detect excessive inputs, then noise cancellation stability improves, but computational complexity and processing time increase
Solution Approach 1:
The patent applies FFT transformation to convert the reference signal to frequency domain before the limiting operation. This preliminary transformation enables subsequent frequency-domain magnitude comparison and leakage calculation to be performed efficiently. By preparing the signal in frequency domain upfront, the system achieves stable noise cancellation with optimized processing time for the critical limiting operation.
3Reliability
If frequency dependent dynamic leakage adjustment is applied, then noise boosting is suppressed and performance stability improves, but the device complexity increases
Solution Approach 1:
The patent implements frequency-dependent leakage adjustment by calculating separate leakage values for different frequency bins. Instead of applying a single uniform leakage factor, the system computes frequency-specific leakage based on the magnitude comparison of transformed reference signals. This local quality approach targets specific frequency regions where noise boosting occurs, improving performance stability while managing controller complexity through selective frequency-domain processing.
Data Source
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AI summary
In at least one embodiment, a system for providing a frequency dependent dynamic leakage for noise cancellation is provided. The system includes a noise cancellation controller and a current limiter. The noise cancellation controller is programmed to perform noise cancellation in a vehicle based on a limited input signal. The current limiter is programmed to receive a reference signal from one of an accelerometer or a loudspeaker and to convert the reference signal from a time domain and into a frequency domain to limit the reference signal. The current limiter is further programmed to generate the limited input signal in response to limiting the reference signal.