Acoustic Feedback Control in Hearing Enhancement Headphones
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Solution Overview
Problem
Headphones often experience acoustic feedback, such as howling or whistling noise, due to the close proximity of microphones and loudspeakers, which negatively impacts user experience, especially when hearing enhancement features are activated to assist users with mild to moderate hearing loss.
Innovation Solution
A wearable audio output device with an adaptive filter-based acoustic feedback cancellation component that estimates and cancels leaked feedback signals, and selectively suppresses feedback through notch filtering, while enabling hearing enhancement and wakeword detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hearing enhancement features are activated to assist users with hearing loss, then audio quality and environmental noise perception are improved, but acoustic feedback (howling or whistling noise) increases due to close proximity of microphones and loudspeakers
Solution Approach 1:
The patent captures the acoustic feedback signal using the microphone, processes it through adaptive filtering to estimate the feedback path, and then subtracts the estimated feedback from the original signal. This converts the harmful feedback into useful information about the feedback path characteristics, which is then used to cancel the feedback. The harmful acoustic feedback is transformed into a beneficial cancellation mechanism that improves overall audio quality while maintaining hearing enhancement.
Solution Approach 2:
The patent introduces an adaptive filter as an intermediary component between the loudspeaker and microphone. This filter models the acoustic feedback path and generates an estimate of the feedback signal. The intermediary filter allows the system to separate the desired environmental noise from the unwanted feedback by processing signals through this intermediate stage, enabling clear audio output without direct coupling between the loudspeaker and microphone.
2Volume of moving object
If microphones and loudspeakers are placed in close proximity for compact headphone design, then device size is reduced, but acoustic feedback increases
Solution Approach 1:
The patent replaces physical separation (mechanical solution) with signal processing (electronic solution). Instead of placing microphones and loudspeakers far apart to prevent feedback, the system uses adaptive digital filtering to model and cancel the feedback path. This substitution allows compact physical design while maintaining feedback suppression through computational methods rather than mechanical distance.
Solution Approach 2:
The patent implements a feedback cancellation loop where the microphone captures both environmental noise and acoustic feedback, the adaptive filter processes this signal to estimate the feedback component, and the estimated feedback is subtracted from the original signal. This closed-loop feedback mechanism continuously adapts to cancel the harmful acoustic feedback generated by the close proximity of components.
Data Source
AI summary
A system configured to perform acoustic feedback control to enable a device to perform hearing enhancement while suppressing acoustic feedback. During hearing enhancement, the device may amplify environmental noise based on a unique hearing profile associated with the user, personalizing equalization settings, a dynamic range, and/or other characteristics to optimize playback audio for the user. The acoustic feedback control may include an acoustic feedback cancellation (AFC) component that uses an adaptive filter to estimate and cancel a feedback signal. In addition, the AFC component may perform entrainment prevention by detecting periodic signals and adjusting an adaptation rate of the adaptive filter accordingly. Separately, the device may selectively suppress acoustic feedback by detecting frequency bands representing acoustic feedback (e.g., squeal detection) and applying one or more notch filter(s) to suppress the selected frequency bands (e.g., squeal suppression).