Headphone Baffle for Error Microphone Phase Alignment
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Solution Overview
Problem
Existing noise cancellation headphones face challenges in achieving optimal performance due to variations in headphone fit and manufacturing tolerances, which affect the acoustic leakage and phase relations between sound paths, making it difficult to accurately adapt anti-noise signals for effective noise cancellation.
Innovation Solution
The implementation of a baffle between the speaker and the error microphone in noise cancellation headphones to delay the sound output, ensuring that the error signal better matches the conditions at the eardrum, thereby refining the anti-noise signal and improving noise cancellation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the error microphone is placed close to the speaker to sense sound output, then the device complexity is reduced, but the measurement precision of the error signal deteriorates due to phase relation mismatch with the eardrum
Solution Approach 1:
The patent introduces a delay element as an intermediary component between the speaker and the error microphone. This delay element compensates for the phase difference caused by the microphone's proximity to the speaker, effectively mediating the signal path to match the eardrum reference point phase relations while maintaining the simple placement configuration
Solution Approach 2:
The patent modifies the time delay parameter of the error microphone signal to compensate for the phase relation mismatch. By adjusting the delay parameter, the system aligns the error signal phase with the eardrum reference point, improving measurement precision without changing the physical microphone placement
2Adaptability or versatility
If adaptive noise cancellation is implemented to compensate for headphone fit variations, then the adaptability improves, but the device complexity increases due to additional filtering and adjustment mechanisms
Solution Approach 1:
The patent implements a feedback mechanism where the error microphone continuously monitors the sound field near the eardrum, and the system automatically adjusts the noise cancellation filter parameters based on this feedback. This closed-loop control enables adaptation to headphone fit variations while managing complexity through intelligent algorithms
Solution Approach 2:
The patent employs dynamic filter parameters that can be adjusted in real-time based on detected acoustic conditions. The system transitions from static to dynamic filtering, allowing the noise cancellation characteristics to adapt to changing headphone-fit conditions and acoustic environments
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 solution enhances the accuracy of noise cancellation by aligning the error signal with the eardrum reference point, leading to improved noise cancellation performance and adaptation, even with variations in headphone fit and manufacturing tolerances.
Implementation Method 1
the sound being output from the speaker is delayed by the baffle at a location of the error microphone
Data Source
AI summary
A noise cancellation enabled headphone to be worn on or over an ear of a user includes a speaker, a feed-forward microphone predominantly sensing ambient sound, an error microphone being arranged in front of the speaker in a primary direction of sound emission of the speaker and adapted to sensing sound being output from the speaker and ambient sound. A baffle is arranged between the speaker and the error microphone in the primary direction of sound emission such that the sound being output from the speaker is delayed by the baffle at a location of the error microphone. An adaptive noise cancellation controller is configured to perform feed-forward noise cancellation based on a feed-forward signal recorded with the feed-forward microphone and filtered with feed-forward filter parameters, and to adjust the feed-forward filter parameters based on an error signal recorded with the error microphone.