Adaptive Noise Filter Leakage Estimation for Earphones
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Solution Overview
Problem
Existing noise cancellation headphones and earphones face challenges in maintaining effective noise cancellation due to variable acoustic leakage, which is not adequately addressed by current technologies, especially in 'leaky' designs that do not provide a consistent seal, leading to instability in adaptive noise cancellation systems.
Innovation Solution
An audio system for ear mountable devices that includes an error microphone and a feedforward microphone, coupled with noise filters and an adaptation engine to estimate and adapt to the leakage condition, allowing for dynamic adjustment of noise cancellation filters to maintain effective noise cancellation despite varying acoustic leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive noise cancellation is used to handle variable acoustic leakage, then noise cancellation performance is improved, but system stability deteriorates due to leakage variations
Solution Approach 1:
The patent implements dynamic adaptation of noise cancellation filters that automatically adjust to changing acoustic leakage conditions. The system transitions from static filter coefficients to dynamic coefficients that adapt in real-time based on detected leakage variations, resolving the contradiction between handling variable leakage and maintaining stability.
Solution Approach 2:
The patent employs feedback mechanisms where the system continuously monitors acoustic leakage conditions and uses this information to adjust filter parameters. This closed-loop control enables the system to maintain stability while adapting to leakage variations, directly addressing the technical contradiction.
2Measurement precision
If multiple sensors are added for off-ear detection to distinguish leakage states, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes existing sensors serve multiple functions - they are used both for their primary purposes and for detecting acoustic leakage conditions. This multi-functionality approach enables accurate leakage detection without adding dedicated sensors, resolving the contradiction between detection accuracy and device complexity.
Solution Approach 2:
The system uses its own operational data and existing sensor inputs to self-diagnose leakage conditions without requiring external dedicated detection hardware. The noise cancellation system itself provides the information needed to assess acoustic leakage, eliminating the need for separate detection sensors.
3Adaptability or versatility
If existing off-ear detection methods are used to distinguish between on-ear and off-ear states, then basic leakage detection is achieved, but precise leakage condition estimation deteriorates
Solution Approach 1:
The patent transitions from binary state detection (on-ear/off-ear) to continuous parameter estimation by analyzing variations in acoustic signals. The system extracts leakage condition information from signal characteristics such as amplitude and frequency variations, enabling precise estimation of leakage severity rather than just binary state detection.
Solution Approach 2:
The patent introduces signal processing algorithms as intermediaries that translate raw sensor data into precise leakage condition estimates. These algorithms act as mediators between the physical acoustic environment and the control system, extracting detailed leakage information that goes beyond simple on/off detection.
Data Source
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AI summary
An audio system (AS) for an ear mountable playback device (HP) comprises a speaker (SP), an error microphone (FB_MIC) configured to predominantly sense sound being output from the speaker (SP) and a further microphone (FF_MIC) configured to predominantly sense ambient sound. The system further comprises a first noise filter (FNF) coupling the further microphone (FF MIC) to the speaker (SP), a second noise filter (SNF) coupling the error microphone (FB MIC) to the speaker (SP) and an adaptation engine (ADP). The adaptation engine is configured to adapt a response of the first noise filter (FNF) depending on error signals from at least the error microphone (FB_MIC), estimate a leakage condition from the response of the first noise filter (FNF), and adapt a response of the second noise filter (SNF) depending on the estimated leakage condition.