Hybrid Active Noise Cancellation Filter Optimization
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Solution Overview
Problem
Existing hybrid active noise cancellation systems face challenges in accurately estimating overall performance when combining feedforward and feedback paths, as separate path designs do not account for interference and speaker response distortions, leading to estimation errors.
Innovation Solution
A computer-implemented method optimizes the feedforward filter based on the feedback filter, adjusting filter coefficients and transfer functions to minimize frequency responses at the user's ear, using regression methods to ensure accurate hybrid ANC system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate FF and FB filter designs are used, then individual path optimization is achieved, but overall hybrid ANC performance estimation is inaccurate
Solution Approach 1:
The patent merges the separate feedforward and feedback filter design processes into a unified hybrid optimization framework. The computer-implemented method simultaneously optimizes both filters by combining their respective transfer functions and performance metrics, allowing the system to account for interactions between the two paths that separate designs cannot capture. This integration enables accurate prediction of overall hybrid ANC performance while maintaining the benefits of both individual path optimizations.
2Reliability
If FB path is applied first, then feedback noise cancellation is achieved, but FF path parameters become distorted
Solution Approach 1:
The patent applies preliminary compensation actions to the feedforward filter design to account for the anticipated influence of the feedback path. Before finalizing the FF filter parameters, the system pre-calculates and compensates for the feedback path's effect on speaker response and transfer functions. This preliminary adjustment ensures that when both paths are combined, the FF filter parameters remain accurate and undistorted, while still achieving effective feedback noise cancellation.
3Ease of manufacture
If FB attenuation is defined at microphone point, then feedback path optimization is simplified, but estimation errors occur at listener's ear
Solution Approach 1:
The patent introduces an intermediary transfer function that models the acoustic path from the feedback microphone to the listener's eardrum. This intermediary element bridges the gap between the simplified microphone-point optimization and the actual eardrum-level performance. By incorporating this transfer function into the optimization algorithm, the system can efficiently design filters at the microphone level while accurately predicting and optimizing performance at the eardrum, eliminating estimation errors without sacrificing design simplicity.
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 approach effectively optimizes the hybrid ANC system by accurately estimating and adjusting filter settings, improving noise cancellation performance and reducing estimation errors, as demonstrated by simulation and measurement results.
Implementation Method 1
ANC is achieved by producing audio signal with equal amplitude but opposite phase to the ambient noises at a listener's ear, thus using the principle of destructive wave interference to cancel unwanted extraneous noise
Data Source
AI summary
A computer-implemented method for automatically optimizing a hybrid active noise cancellation system, the hybrid active noise cancellation system comprising a feedback filter and a feedforward filter, the method comprising optimizing the feedforward filter, thereby optimizing the hybrid active noise cancellation system, wherein optimization of the feedforward filter is dependent on the feedback filter.