Active Noise Reduction Gain Control for Pressure Feedback Instability
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Solution Overview
Problem
Feedback instability in active noise reduction systems due to pressure-related disturbances, which can lead to instability and distortion, is not effectively mitigated by existing technologies.
Innovation Solution
Incorporating a pressure-related disturbance detector within the active noise reduction circuitry to dynamically adjust the loop gain of the feedback loop, distinguishing between pressure changes caused by external noise and those caused by earpiece movement, and using a variable gain component within the feedback loop to mitigate instability without sacrificing noise attenuation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the loop gain of the feedback loop is increased to improve noise attenuation performance, then the noise reduction capability is improved, but feedback instability and distortion occur due to pressure-related disturbances
Solution Approach 1:
The system dynamically adjusts the loop gain based on detected pressure changes. A detection circuit monitors pressure within the acoustic environment and triggers gain compensation when pressure changes exceed a threshold, indicating earpiece movement. This dynamic adjustment allows the system to maintain high gain for noise attenuation while reducing gain during pressure disturbances to prevent instability and distortion.
Solution Approach 2:
The system employs a feedback mechanism where the detection circuit continuously monitors pressure changes and feeds this information to the gain compensation circuit. When pressure changes indicate earpiece movement, the feedback loop automatically reduces the loop gain to maintain stability. This closed-loop feedback ensures the system adapts to changing conditions while maintaining both performance and stability.
2Stability of the object's composition
If the loop gain is reduced to mitigate feedback instability, then stability is improved, but noise attenuation performance deteriorates
Solution Approach 1:
The system periodically monitors pressure changes through the detection circuit and applies gain compensation only when necessary. The detection circuit continuously checks for pressure changes exceeding the threshold, and the gain compensation is applied intermittently only during pressure-related disturbances. This periodic monitoring and selective compensation allows the system to maintain high gain and optimal noise attenuation performance during normal operation while temporarily reducing gain only when instability occurs.
3Stability of the object's composition
If a pressure-related disturbance detector is added to dynamically adjust loop gain, then feedback instability is mitigated, but device complexity increases
Solution Approach 1:
The detection circuit serves multiple functions: it monitors pressure changes within the acoustic environment, detects earpiece movement by comparing pressure changes against a threshold, and triggers gain compensation when disturbances are detected. By consolidating these detection and control functions into a single integrated circuit, the system achieves effective instability mitigation without proportionally increasing overall device complexity.
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
The solution effectively mitigates feedback instability caused by pressure-related disturbances, maintaining high loop gain during normal operation and providing enhanced low-frequency plant output and passive attenuation, thus maintaining system stability and noise reduction performance.
Implementation Method 1
detection circuitry configured to detect a change in pressure within the acoustic environment caused by movement of the member
Implementation Method 2
The anti-noise signal is provided to a noise cancellation driver, which transduces the signal into a sound wave
Implementation Method 3
When the anti-noise sound wave produced by the noise cancellation driver combines in the acoustic cavity with the noise sound wave, the two sound waves cancel one another due to destructive interference
Data Source
AI summary
An apparatus includes a member configured to form an acoustic seal around a portion of an acoustic environment, and active noise reduction circuitry. The active noise reduction circuitry includes: detection circuitry configured to detect a change in pressure within the acoustic environment caused by movement of the member, and gain compensation circuitry configured to change a loop gain of a feedback loop in response to the detected change in pressure.