Variable Compressor for Headphone Audio Feedback Path
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Solution Overview
Problem
Headphones with feedback-type acoustic noise cancellation (ANC) face issues with playback distortion due to loose or improper fitting, which causes the amplifier to overload at high volumes, leading to inconsistent sound quality across different users.
Innovation Solution
A method involving an audio feedback signal from the internal microphone, filtered and compressed with variable compressor parameters adjusted based on user volume settings to prevent amplifier overload, ensuring undistorted playback by reducing the likelihood of clipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the equalization filter applies large gain to compensate for acoustic energy leaking due to loose fitting, then the desired timbral characteristics of music are maintained, but the amplifier becomes overloaded and playback becomes distorted
Solution Approach 1:
The patent applies dynamics by making the equalization filter gain variable rather than fixed. The gain is dynamically adjusted based on the detected acoustic leakage level, allowing the system to maintain consistent timbral characteristics when leakage is present while preventing amplifier overload by reducing gain when leakage is detected, thus resolving the contradiction between maintaining sound quality and preventing distortion
Solution Approach 2:
The patent changes the parameter of filter gain from a static value to a dynamically adjustable parameter. By detecting acoustic leakage and adjusting the equalization filter gain accordingly, the system adapts to different fitting conditions, maintaining timbral consistency without causing amplifier overload, thereby resolving the technical contradiction
2Adaptability or versatility
If the headphone fits loosely or improperly, then the equalization filter must apply large gain to maintain timbral characteristics, but this causes amplifier overload and distortion at high volumes
Solution Approach 1:
The patent employs feedback by detecting the acoustic leakage level and using this information to adjust the equalization filter gain. The system continuously monitors the acoustic environment and adapts the filter parameters accordingly, enabling the headphone to compensate for loose fitting while preventing amplifier overload, thus resolving the contradiction between adaptability and harmful effects
Data Source
AI summary
A processor is configured to perform headphone playback with a playback audio signal. The processor produces a feedback signal from an internal microphone, compresses the feedback signal according to a variable compressor setting, and determines a context of usage of the headphone, as being one of running or jogging, transportation, and critical listening. In response, the processor changes the variable compressor setting and drives the headphone speaker with the compressed feedback signal combined with the playback audio signal. Other aspects are also described and claimed.