Adaptive Filter Noise Cancellation Using Segmented Microphone Arrays
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Solution Overview
Problem
Existing noise canceling technologies face challenges in achieving sufficient noise canceling performance due to difficulties in creating perfect unidirectional microphones, maintaining flat frequency characteristics, and accurately recording sound fields, leading to degradation in noise canceling performance.
Innovation Solution
A signal processing device and method that detect control area internal noise using a microphone array and update the adaptive filter coefficients based on this detection to reduce external noise, preventing filter divergence and improving noise canceling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a unidirectional microphone is used as a reference microphone or error microphone to reduce influence from internal noise, then the directivity is improved, but it is difficult to actually create a microphone having a perfect unidirectionality and the influence of noise transmitted from the inside of the control area is still received
Solution Approach 1:
The patent divides the noise detection function into two separate components: reference microphones that capture external noise and detection microphones that capture internal noise. This segmentation allows each microphone type to be optimized for its specific function, with reference microphones positioned to primarily capture external noise and detection microphones positioned inside the control area to capture internal noise, thereby resolving the contradiction between directivity and reliability
Solution Approach 2:
The patent introduces detection microphones as an intermediary component that specifically monitors internal noise within the control area. These detection microphones act as a mediator between the internal noise sources and the adaptive filter update process, providing separate internal noise information that prevents the reference microphones from needing to achieve perfect unidirectionality while maintaining reliable noise canceling performance
2Object-affected harmful factors
If a microphone with unidirectionality is used, then the influence from internal noise is reduced, but it is difficult to keep frequency characteristics flat and the variation between individual microphones is large, whereby it is difficult to accurately record a sound field
Solution Approach 1:
The patent segments the microphone system into reference microphones for external noise capture and detection microphones for internal noise monitoring. This segmentation allows the detection microphones to be positioned optimally for internal noise detection without requiring flat frequency characteristics or high unidirectionality, while the reference microphones can be optimized for sound field recording, thereby resolving the contradiction between reducing internal noise influence and maintaining measurement precision
Solution Approach 2:
The patent uses detection microphones to create a separate copy of the internal noise signal that is used specifically for controlling adaptive filter updates. This copying approach allows the system to monitor internal noise without requiring the primary reference microphones to perfectly reject internal noise, enabling the use of microphones with simpler directional characteristics while maintaining accurate sound field recording capabilities
3Reliability
If noise generated inside the control area is detected by the reference microphone or error microphone, then the adaptive filter diverges so that noise canceling performance is degraded, but using unidirectional microphones still allows some internal noise to be received
Solution Approach 1:
The patent segments the noise detection function into reference microphones for external noise and detection microphones for internal noise. This segmentation ensures that the adaptive filter uses separate signal sources for external noise cancellation and internal noise monitoring, preventing internal noise from contaminating the external noise reference signal and causing filter divergence, thereby resolving the contradiction between filter stability and internal noise rejection
Solution Approach 2:
The detection microphones serve as an intermediary that provides a dedicated internal noise monitoring channel. This intermediary component allows the system to detect and account for internal noise without requiring the reference microphones to perfectly reject it, ensuring adaptive filter stability by using the detection microphone signals to control filter updates rather than relying solely on reference microphone signals that may contain internal noise
Data Source
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AI summary
The present technology relates to a signal processing device and method, and a program that are capable of improving noise canceling performance. A signal processing device includes: a noise detection unit that detects control area internal noise generated in a control area formed by a microphone array; and a control unit that controls update of a filter coefficient of an adaptive filter, used to generate a signal of an output sound output by a speaker array, on the basis of a detection result of the control area internal noise in order to reduce external noise to a noise canceling area formed by the speaker array. The present technology can be applied to a spatial noise control device.