Hear-Through Filter for Acoustic Transparency in ANC Earbuds
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Solution Overview
Problem
Active noise cancellation (ANC) devices often impede users from hearing desired external sounds, even when the ANC system is not active, due to passive attenuation, which can lead to inadequate acoustic transparency and the need for users to remove the device to perceive environmental sounds or communicate effectively.
Innovation Solution
The implementation of a hear-through filter and feedback ANC filter system that allows external sounds to be passed through while canceling self-voice, using adaptive and fixed filters to adjust for variations in earbud fit and individual hearing profiles, ensuring acoustic transparency by aligning internal and external microphone signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive acoustic isolation is used to block external noise, then noise cancellation performance is improved, but acoustic transparency deteriorates
Solution Approach 1:
The audio signal is segmented into different components (external sounds, self-voice, noise) that are processed separately through different filters (hear-through filter, feedback ANC filter) before being combined, allowing selective transmission of desired sounds while blocking noise
Solution Approach 2:
A hear-through filter is introduced as an intermediary component that allows external sounds to pass through the passive acoustic isolation barrier, mediating between the noise-blocking function and the acoustic transparency requirement
2Loss of information
If hear-through filter is used to improve acoustic transparency, then external sound perception is improved, but self-voice cancellation effectiveness deteriorates
Solution Approach 1:
The signal processing system segments external sounds and self-voice into separate processing paths, applying different filter characteristics to each path, allowing external sounds to be enhanced while self-voice is selectively canceled
Solution Approach 2:
Different filter characteristics are applied to different frequency ranges and signal types - the hear-through filter is optimized for external sound frequencies while the feedback ANC filter targets self-voice frequencies, creating local quality variations in the filtering approach
3Loss of information
If adaptive filtering is used to adjust for earbud fit variations, then acoustic transparency consistency is improved, but device complexity increases
Solution Approach 1:
The filter characteristics are made dynamic and adaptive, automatically adjusting to match the user's specific earbud fit and hearing profile, ensuring consistent acoustic transparency across different users and conditions
Solution Approach 2:
The system changes filter parameters (frequency response, gain, phase) based on measured acoustic characteristics of the user's ear canal and earbud fit, optimizing performance for each individual user
Data Source
AI summary
Methods, systems, computer-readable media, and apparatuses for audio signal processing are presented. A device for audio signal processing includes a memory configured to store audio data and a processor coupled to the memory. The processor is configured to use an adaptation filter to adapt update filter coefficients of an update filter. The update filter coefficients are adapted based on a difference between an internal microphone signal and an output of the adaptation filter. An input of the adaptation filter is based on an external microphone signal. The processor is also configured to output an output signal from a hear-through filter. The hear-through filter includes the update filter and the adaptation filter. The processor is further configured to cause a loudspeaker to produce an audio output signal based on the output signal of the hear-through filter.