ANR Circuit Dynamic Gain Control for Talk-Through
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Solution Overview
Problem
Existing personal active noise reduction (ANR) devices face issues with high power consumption, limited frequency range for noise cancellation, and sometimes introduce more noise than they reduce, while also potentially creating unpleasant sounds.
Innovation Solution
The ANR circuit in personal ANR devices monitors environmental noise levels and adjusts the feedback-based noise reduction by varying the loop gain and filter coefficients to optimize noise cancellation, allowing for dynamic changes in noise reduction based on sound levels and frequencies, and includes mechanisms for reducing noise during talk-through operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback-based ANR is continuously applied at high gain to maximize noise cancellation, then noise reduction effectiveness is improved, but power consumption increases and instability may occur
Solution Approach 1:
The patent implements dynamic adjustment of the feedback loop gain based on environmental noise levels. The system transitions from static high gain to dynamic variable gain, adjusting the feedback ANR strength in real-time according to actual noise conditions, thereby optimizing both noise reduction effectiveness and power consumption.
Solution Approach 2:
The system changes the gain parameter of the feedback loop based on detected noise levels. When noise exceeds a threshold, feedback ANR is enabled with appropriate gain; when noise is low, gain is reduced or disabled. This parameter adjustment resolves the contradiction by matching power consumption to actual noise reduction needs.
2Reliability
If feedback loop gain is increased to improve noise cancellation across wider frequency range, then ANR performance is improved, but system stability deteriorates and unpleasant sounds are generated
Solution Approach 1:
The patent adjusts the feedback loop gain parameter dynamically based on noise level thresholds. By changing the gain parameter adaptively rather than using fixed high gain, the system achieves effective noise cancellation while avoiding the unpleasant sounds and instability that result from excessively high gain settings.
Solution Approach 2:
The system uses feedback from the noise detection mechanism to continuously monitor environmental noise levels and adjust the feedback loop gain accordingly. This closed-loop feedback control ensures that gain is increased only when necessary for noise cancellation, preventing the generation of unpleasant sounds while maintaining stability.
3Stability of the object's composition
If feedback ANR is applied continuously to maintain noise reduction, then noise cancellation consistency is improved, but power consumption increases due to unnecessary operation in low noise environments
Solution Approach 1:
The patent implements periodic monitoring of noise levels with threshold-based activation. Instead of continuous operation, the feedback ANR is periodically evaluated against noise thresholds and activated only when needed. This periodic action maintains noise reduction consistency during noisy periods while conserving power during quiet periods.
Solution Approach 2:
The system uses its own noise detection capability to automatically determine when feedback ANR should be activated or deactivated. This self-service mechanism eliminates the need for continuous operation by having the system independently assess whether noise reduction is currently necessary, thereby reducing power consumption while maintaining consistency when needed.
4Duration of action of stationary object
If feedback ANR operates without talk-through detection to maintain noise reduction, then noise cancellation continuity is improved, but user communication capability deteriorates
Solution Approach 1:
The patent incorporates feedback from a talk-through detection mechanism that monitors for user speech or communication needs. When talk-through is detected, the system automatically adjusts or suspends feedback ANR operation, allowing user communication while maintaining noise cancellation during normal use. This feedback-based control resolves the contradiction between continuous noise reduction and communication capability.
Data Source
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AI summary
An active noise reduction (ANR) circuit comprising: a digital feed-forward ANR pathway coupled to a feed-forward microphone, to detect environmental sounds in an environment external to a casing, and coupled to a first acoustic driver to output sounds within the casing; and a user input; wherein the digital feed-forward ANR pathway applies a filter using a first set of coefficients to convert signals from the feed-forward microphone to feed-forward anti-noise sounds to reduce environmental sounds within the casing, and in response to activation of the user input, the digital feed-forward ANR pathway applies the filter using a second set of coefficients, the second set of coefficients reducing the degree of feed-forward ANR to enable human speech sounds in the environment external to the casing to be conveyed from the feed-forward microphone to the acoustic driver with less reduction than provided by the first set of coefficients.