Gradual Reset of Adaptive Filter Coefficients
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Solution Overview
Problem
Existing adaptive noise cancellation systems in personal audio devices often introduce audible artifacts, such as pops or clicks, when resetting filter coefficients, which can disrupt the listening experience due to sharp discontinuities in the output signal.
Innovation Solution
An integrated circuit with an adaptive filter and a coefficient control block that gradually increments filter coefficients from initial to final values during a reset, minimizing the introduction of audible artifacts by smoothing the transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filter coefficients are reset instantaneously to restore the system from a non-ideal state, then the system reliability is improved, but audible artifacts (pops or clicks) are introduced due to sharp discontinuity in the output signal
Solution Approach 1:
The coefficient reset process is segmented into multiple incremental steps rather than a single instantaneous change. Each step updates a portion of the coefficients, dividing the harmful discontinuous event into smaller, less perceptible changes that collectively achieve the same system restoration goal
Solution Approach 2:
The coefficient update is performed periodically over multiple time intervals rather than all at once. This periodic action allows the system to gradually transition from the non-ideal state to the restored state, with each periodic update being small enough to avoid generating audible artifacts while collectively achieving system recovery
2Object-generated harmful factors
If filter coefficients are updated gradually in multiple steps, then audible artifacts are reduced, but the time required to restore the system increases
Solution Approach 1:
The system applies partial action by updating only a portion of the coefficients in each step rather than all coefficients simultaneously. This partial updating approach reduces the perceptibility of each individual update step while still achieving complete system restoration over the multi-step process
Solution Approach 2:
The system changes the parameter of coefficient update magnitude from a large instantaneous change to a series of smaller incremental changes. By controlling the step size and number of iterations, the system optimizes the balance between artifact reduction and restoration time, adjusting the rate of parameter change to match perceptual thresholds
Data Source
AI summary
An integrated circuit for implementing at least a portion of a personal audio device may include a processing circuit to implement an adaptive filter having a response that generates an anti-noise signal to reduce the presence of the ambient audio sounds at an error microphone, implement a coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone signal by computing coefficients that determine the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, and responsive to detecting a condition that triggers a reset of the adaptive filter, increment the coefficients in a plurality of steps from initial values of the coefficients at a time of triggering the reset to final values of the coefficients at a conclusion of the reset.