Controllable ANC Gain Levels for Hiss Reduction
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Solution Overview
Problem
Conventional active noise cancellation (ANC) systems introduce a noticeable hiss in quiet environments due to excessive noise reduction, and some users find strong ANC to be unpleasant, even when there is no hiss.
Innovation Solution
A controllable-level ANC system that adjusts the ANC gain based on ambient noise levels, providing multiple ANC gain levels and using a processor to determine a revised ANC level by comparing microphone signals to thresholds, thereby reducing feedback ANC gain when the ambient noise level is less than the ANC noise level, and outputting a signal corresponding to the revised ANC level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional ANC systems operate with high gain to maximize noise reduction, then ambient noise is effectively reduced, but ANC hiss becomes noticeable in quiet environments
Solution Approach 1:
The patent implements dynamic adjustment of ANC gain levels based on real-time ambient noise detection. The system transitions from static high gain to dynamic multi-level gain control, switching between different ANC strength levels (first level, second level, third level) according to ambient conditions. This resolves the contradiction by making the system adaptive: high gain is applied only when ambient noise exceeds thresholds, while lower gain is used in quiet environments to minimize hiss.
Solution Approach 2:
The system changes the gain parameter of the ANC filter based on detected ambient noise levels. By monitoring the ambient noise signal and comparing it against threshold values, the system adjusts the gain parameter dynamically - using higher gain values when noise is present and lower gain values when the environment is quiet, thereby balancing noise reduction effectiveness with hiss minimization.
2Object-affected harmful factors
If strong ANC gain is applied continuously, then noise reduction is maximized, but user comfort deteriorates due to unpleasant listening experience
Solution Approach 1:
The system dynamically adjusts ANC strength to match ambient conditions rather than applying continuous strong gain. By implementing multiple ANC levels and transitioning between them based on real-time noise detection, the system provides strong noise reduction only when necessary, while offering gentler ANC in quieter environments, thereby maintaining user comfort while preserving noise reduction effectiveness.
Solution Approach 2:
The system applies partial ANC action (lower gain levels) in quiet environments rather than excessive strong ANC gain. By using a first ANC level for moderate conditions and a second, lower ANC level for quiet conditions, the system avoids over-cancellation that causes discomfort, applying only the necessary degree of noise reduction for each environmental context.
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
Reduces ANC hiss perceived by users and provides a more pleasant listening experience by adjusting ANC gain levels, ensuring that the noise floor with ANC is either equal to or less than the ambient noise level, thereby eliminating unwanted noise in quiet environments.
Implementation Method 1
The noise reduction is typically achieved by playing an anti-noise signal through the headphone's speakers. The anti-noise signal is an approximation of the negative of the undesired noise signal that would be in the ear cavity in the absence of ANC. The undesired noise signal is then neutralized when combined with the anti-noise signal.
Data Source
AI summary
A system including an automatic noise canceling (ANC) headphone and a processor. The ANC headphone has a microphone configured to generate a microphone signal and at least two non-zero ANC gain levels. The processor is configured to receive the microphone signal, determine a characteristic of the microphone signal, and identify a revised ANC level from the ANC gain levels based on a comparison of the characteristic to at least one threshold. Methods are also disclosed.