Headphone Feedback Suppression via Dynamic Gain Control
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Solution Overview
Problem
Audio devices that occlude external sounds, such as headphones, struggle to allow users to hear important external noises like approaching cars or friend's voices while listening to media streams, due to environmental overlay instability caused by feedback between microphones and speakers.
Innovation Solution
A control system in audio devices determines media and microphone audio gains for specific frequency bands to mitigate feedback risk, adjusting gains based on feedback risk control values and detecting headphone removal or improper positioning to ensure external sounds are audible above media signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If headphones occlude external sounds to eliminate distortion and provide flat equalization, then audio quality is improved, but the ability to hear important external noises deteriorates
Solution Approach 1:
The patent introduces an intermediary system consisting of external microphones, processing circuitry, and speakers that mediate between the occluded external environment and the user's ear. The microphones capture external sounds, the processing circuitry analyzes and enhances them, and the speakers reproduce them internally, allowing users to hear external noises without removing the headphones while maintaining audio quality isolation
Solution Approach 2:
The patent replaces the mechanical/acoustic system of sound transmission through the ear canal with an electronic system. Instead of relying on physical sound waves traveling through the occluded ear canal, the system uses microphones to convert external sounds to electrical signals, processes these signals electronically, and uses speakers to convert them back to sound waves internally, substituting electronic processing for mechanical sound transmission
2Object-affected harmful factors
If environmental microphone signals are boosted to be audible above media signals, then external sound audibility is improved, but feedback risk between microphone and speaker increases
Solution Approach 1:
The patent applies different processing characteristics to different frequency components of the environmental microphone signals. The processing circuitry analyzes specific frequency ranges and applies selective enhancement and suppression, allowing certain frequencies to be boosted for audibility while suppressing frequencies that would cause feedback, creating local quality differences in the signal processing
Solution Approach 2:
The patent introduces a feedback control mechanism where the processing circuitry continuously monitors the relationship between microphone input and speaker output, detecting conditions that lead to feedback loops. When feedback is detected or predicted, the system automatically adjusts signal processing parameters to eliminate the feedback condition while maintaining external sound audibility
3Adaptability or versatility
If rapid gain adjustments are made to environmental microphone signals to track changing signal levels, then adaptability is improved, but environmental overlay instability increases
Solution Approach 1:
The patent implements dynamic signal processing where gain and filtering parameters are continuously adjusted based on real-time analysis of environmental microphone signal characteristics. The system adapts to changing acoustic conditions, speaker positions, and user behavior while maintaining stability through controlled adjustment rates and predictive algorithms that anticipate instability conditions
4Object-affected harmful factors
If maximum gain is applied to environmental microphone signals to ensure external sounds are heard, then external sound audibility is improved, but feedback between microphone and speaker occurs
Solution Approach 1:
The patent dynamically changes multiple signal processing parameters including gain, filtering characteristics, and frequency weighting based on real-time conditions. Rather than applying a fixed maximum gain, the system adjusts parameters continuously to optimize external sound audibility while staying below feedback thresholds, using techniques like frequency-dependent gain adjustment and adaptive filtering
Data Source
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AI summary
An audio processing method may involve receiving media input audio data corresponding to a media stream and headphone microphone input audio data, determining a media audio gain for at least one of a plurality of frequency bands of the media input audio data and determining a headphone microphone audio gain for at least one of a plurality of frequency bands of the headphone microphone input audio data. Determining the headphone microphone audio gain may involve determining a feedback risk control value, for at least one of the plurality of frequency bands, corresponding to a risk of headphone feedback between at least one external microphone of a headphone microphone system and at least one headphone speaker and determining a headphone microphone audio gain that will mitigate actual or potential headphone feedback in at least one of the plurality of frequency bands, based at least partly upon the feedback risk control value.