Adaptive Noise Cancellation Secondary Path Modeling
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Solution Overview
Problem
Traditional adaptive noise cancellation systems in personal audio devices degrade in performance as the distance between the error microphone and the listener's eardrum increases, due to the decrease in the gain of the transfer function from the error reference point to the drum reference point, leading to suboptimal noise cancellation.
Innovation Solution
The implementation of an integrated circuit with secondary path estimate adaptive filters and coefficient control blocks that generate anti-noise signals by modeling the electro-acoustic paths of transducers, minimizing playback corrected errors based on error microphone signals, and comparing responses to adjust anti-noise signal generation effectively across audio channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the distance between the error microphone and the listener's eardrum increases, then the device can be positioned more comfortably or for different listening scenarios, but the noise cancellation performance degrades due to decreased gain of the transfer function
Solution Approach 1:
The system dynamically adapts the secondary path filter response based on detected acoustic environment changes and distance conditions. The coefficient control block adjusts filter parameters in real-time to maintain optimal noise cancellation performance across varying distances between the error microphone and eardrum, transforming a static system into one that responds to positional changes.
Solution Approach 2:
The patent modifies the secondary path filter response parameters (gain, frequency response) based on the detected distance or acoustic environment. By changing these parameters adaptively, the system compensates for the natural degradation of transfer function gain that occurs with increased distance, thereby maintaining noise cancellation effectiveness.
2Device complexity
If traditional adaptive noise cancellation systems are used without secondary path compensation, then the system structure remains simple, but performance degrades when the error microphone is positioned far from the eardrum
Solution Approach 1:
The patent introduces a secondary path estimate adaptive filter as an intermediary component between the error microphone signal and the anti-noise generation process. This intermediary filter models and compensates for the electro-acoustic path variations, acting as a mediator that corrects the degraded signal relationship caused by distance without requiring complete system redesign.
Solution Approach 2:
The system performs preliminary modeling of the secondary path (electro-acoustic transfer function) to predict and compensate for performance degradation before it significantly impacts noise cancellation. By pre-characterizing the path and preparing compensation filters in advance, the system maintains performance without reactive complex adjustments.
Data Source
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AI summary
Systems and methods of the present disclosure include analyzing and comparing transfer functions associated with a plurality of electro-acoustic paths for transducers of a personal audio device to determine proximity of the transducers to respective ears of a listener of the personal audio device, quality of acoustic seals associated with the transducers, and for one or more other purposes.