Active Noise Control Auto-Calibration Gain Compensation
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Solution Overview
Problem
Current Active Noise Control (ANC) systems in audio devices like headphones and earbuds face challenges in achieving uniform noise attenuation across frequencies, with feedback-based systems being bandlimited, leading to instability and variations in performance due to component variations during manufacturing.
Innovation Solution
A method for calibrating feedback-based ANC systems by determining and applying gain values to compensate for variations in microphone and speaker driver sensitivity, using a test fixture to measure plant and coupler responses, and calculating logarithmic gain values to maximize cancellation performance while ensuring stability, thereby addressing component variations and frequency response issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback-based ANC systems are used to reduce unwanted sound, then noise cancellation capability is improved, but system stability deteriorates due to bandlimiting and component variations
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements and calculating compensation values before the ANC system operates. The system pre-determines the actual frequency responses of the microphone and speaker driver, then pre-calculates compensation values that are stored and applied during operation to counteract component variations and maintain stability.
Solution Approach 2:
The patent applies parameter changes by measuring and adjusting the gain values of the microphone and speaker driver based on their actual frequency responses. The system calculates compensation values that modify the operational parameters of these components to account for manufacturing variations, thereby maintaining system stability while preserving noise cancellation capability.
2Manufacturing precision
If component variations during manufacturing are present, then manufacturing precision is reduced, but calibration complexity increases to compensate
Solution Approach 1:
The patent applies self-service by enabling the ANC system to automatically calibrate itself using built-in microphones and test signals. The system performs self-diagnosis and self-adjustment by measuring its own component responses and applying compensation values without requiring external calibration equipment or manual intervention, thereby reducing calibration complexity despite component variations.
Solution Approach 2:
The patent applies feedback by using the ear device's own microphone to measure the actual frequency response of the speaker driver and microphone chain. This feedback mechanism allows the system to detect component variations and automatically adjust compensation values to maintain consistent performance across different manufactured units.
3Reliability
If gain values are adjusted to compensate for component variations, then noise cancellation performance is improved, but measurement precision requirements increase
Solution Approach 1:
The patent applies periodic action by using sweep signals or tone bursts at different frequencies to measure the frequency response of the microphone and speaker driver. The system periodically excites the system at various frequencies and measures the response, building up the complete frequency response profile through repeated measurements across the frequency spectrum.
Solution Approach 2:
The patent applies partial action by measuring and compensating for frequency responses within the specific cancellation bandwidth of the ANC system. Rather than attempting to measure and compensate across the entire audible frequency range, the system focuses measurements and adjustments on the relevant frequency band where noise cancellation is effective, reducing measurement precision requirements outside this band.
Data Source
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AI summary
A method of calibrating a feedback-based noise cancellation system of an ear device may involve obtaining a measured plant response of the ear device, obtaining a reference plant response value and determining a plant response variation between the reference plant response value and a value corresponding to the measured plant response. The method may involve obtaining a measured a coupler response of the ear device, obtaining a reference coupler response value and determining a coupler response variation between the reference coupler response value and a value corresponding to the measured coupler response. The method may involve determining, based at least in part on the plant response variation and the coupler response variation, a microphone signal gain correction factor and applying the microphone signal gain correction factor to ear device microphone signals that are input to a feedback loop of the feedback-based noise cancellation system.