ANC Microphone Array Symmetry for Robust Secondary Path Estimation
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Solution Overview
Problem
Active noise control (ANC) systems face instability and reduced noise damping due to variations in secondary path transfer characteristics, which can occur from changes in the number of listeners, movement, or environmental changes, leading to mismatched model transfer characteristics and smaller 'sweet spots'.
Innovation Solution
A method involving a microphone array positioned symmetrically to a desired listening position, where test signals are used to calculate and average numerical representations of secondary path transfer characteristics, providing a robust estimation for use in ANC systems to improve noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ANC systems use standard microphone positioning and secondary path modeling, then the system is simpler to implement, but the noise damping becomes unstable and the sweet spot size reduces due to variations in transfer characteristics
Solution Approach 1:
The patent divides the microphone array into multiple individual microphones positioned at different locations around the listening position. Each microphone captures acoustic signals from its specific position, and the system processes these segmented measurements to calculate the secondary path transfer characteristic. This segmentation allows the system to account for spatial variations in acoustic fields and improves robustness against transfer characteristic variations without requiring a single complex measurement system.
Solution Approach 2:
The patent transitions from a single-point measurement approach to a multi-dimensional spatial measurement approach by using multiple microphones arranged in different positions around the listening position. This dimensional expansion from one measurement point to multiple spatial points enables the system to capture the full spatial distribution of acoustic fields, providing more comprehensive information about secondary path characteristics and improving overall system reliability.
2Measurement precision
If the system uses a single microphone for measurement, then the device complexity is reduced, but the measurement precision of secondary path transfer characteristics deteriorates due to positioning errors and environmental variations
Solution Approach 1:
The patent combines the measurements from multiple microphones into a unified estimation of the secondary path transfer characteristic. By merging the data from all individual microphones and processing them together, the system achieves a more precise and robust estimation that is less sensitive to individual microphone positioning errors or environmental variations at any single location, while the computational complexity remains manageable through efficient signal processing techniques.
Solution Approach 2:
The patent uses multiple microphones as copies of the same measurement function, with each microphone serving as an independent sensor that captures the acoustic field from its position. These copies provide redundant information that can be processed to create a more reliable estimate of the secondary path characteristics, compensating for potential errors in any single measurement and improving overall measurement precision without requiring a single complex sensor system.
3Adaptability or versatility
If the ANC system adapts to changes in secondary path characteristics, then the noise cancellation performance is improved, but the system complexity and computational requirements increase
Solution Approach 1:
The patent performs preliminary measurements of the secondary path transfer characteristic using the microphone array before the actual noise cancellation operation begins. By pre-characterizing the acoustic paths and storing this information, the system is prepared to handle variations during operation without requiring complex real-time adaptation algorithms. This preliminary action reduces the computational burden during active noise cancellation while maintaining high adaptability to changes in the acoustic environment.
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
This approach enhances the robustness of ANC systems by reducing susceptibility to microphone positioning errors and variations in secondary path transfer characteristics, maintaining effective noise damping and sweet spot size.
Implementation Method 1
reproducing at least one test signal using a loudspeaker arranged within the listening room to generate an acoustic signal
Implementation Method 2
The acoustic signal is measured with the microphones of the microphone array to obtain a microphone signal from each microphone of the microphone array
Implementation Method 3
generate a compensation sound signal with the same amplitude and frequency components for each noise signal to be suppressed, but with a phase shift of 180° with respect to the noise signal. The compensation sound signal interferes destructively with the noise signal
Data Source
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AI summary
A method for determining an estimation of a secondary path transfer characteristic in an ANC system is described herein. In accordance with one example of the invention, the method includes the positioning of a microphone array in a listening room symmetrically with respect to a desired listening position and reproducing at least one test signal using a loudspeaker arranged within the listening room to generate an acoustic signal. The acoustic signal is measured with the microphones of the microphone array to obtain a microphone signal from each microphone of the microphone array, and a numerical representation of the secondary path transfer characteristic is calculated for each microphone signal based on the test signal and the respective microphone signal. The method further includes averaging the calculated numerical representations of the secondary path transfer characteristic to obtain the estimation of the secondary path transfer characteristic to be used in the ANC system.