Adaptive Headphone ANC Filter for Consistent Noise Cancellation
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Solution Overview
Problem
Existing headphones with acoustic noise cancellation (ANC) technology experience varying performance due to inconsistent fitting on different users' ears, leading to inconsistent noise reduction across different users and environments.
Innovation Solution
An adaptive digital filter C is added to the audio signal feedback path of a headphone system, coupled with a fixed filter G, which adapts online based on the estimated transfer function of the path from the speaker to the internal microphone, operating over a wide frequency band to enhance ANC performance across varying fits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ANC filter is used, then low frequency noise cancellation is achieved, but performance varies greatly across different users due to fitting variations
Solution Approach 1:
The patent applies dynamics by making the filter C adaptive and adjustable in real-time based on the measured acoustic path characteristics. The filter coefficients are dynamically updated using system identification techniques to match each user's unique ear fit, transforming a static filter into a dynamic one that adapts to varying conditions.
Solution Approach 2:
The patent changes the parameters of the feedback filter C based on the measured transfer function of the acoustic path. By adjusting filter coefficients according to the identified acoustic characteristics, the system adapts to different users and fitting conditions, resolving the contradiction between consistency and adaptability.
2Reliability
If ANC filter is designed for low frequency band, then ANC effectiveness is achieved, but wide frequency band performance is not addressed
Solution Approach 1:
The patent makes the feedback filter C serve multiple functions: it operates across the entire audio frequency band (not just low frequencies), provides system identification capability, and delivers ANC performance. This multi-functionality resolves the contradiction by making the filter universal in its applicability across different frequency ranges.
Solution Approach 2:
The filter C is designed to be adaptive across the full audio frequency band, dynamically adjusting its characteristics based on the measured acoustic path. This allows the system to maintain effectiveness across wide frequency ranges while adapting to individual user characteristics.
3Device complexity
If fixed filter is used in feedback path, then system simplicity is maintained, but performance consistency across users deteriorates
Solution Approach 1:
The patent implements feedback by measuring the acoustic path characteristics through the internal microphone and using this information to adaptively adjust the filter C coefficients. This feedback loop enables the system to maintain performance consistency across different users while adding only minimal complexity through the use of standard adaptive filtering algorithms.
Data Source
AI summary
An internal microphone signal of a headphone is filtered by i) a first filter G that, as part of an acoustic noise cancellation, ANC, subsystem, produces an anti-noise audio signal, and ii) a second filter C to produce a feedback audio signal. An estimate of a transfer function of a path S is determined, wherein the path S is from i) an input of a speaker of the headphone to ii) the internal microphone signal. The second filter C is adapted based on the estimate of the transfer function of the path S drives an input of a speaker of the headphone. Other embodiments are also described.