Adaptive Noise Canceling Signal Processing Device
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Solution Overview
Problem
Current noise canceling technologies, particularly in audio headphones and earphones, face challenges in effectively canceling low-frequency external sounds and often generate unnecessary cancellation signals when external noise is not present, leading to discomfort for the user.
Innovation Solution
A signal processing device that uses a correlation calculation unit to determine the correlation between sound pickup signals from a microphone outside and inside a noise canceling region, controlling the generation and output of cancellation signals based on this correlation to prevent unnecessary noise canceling processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active noise canceling is continuously performed without correlation detection, then low-frequency external sounds can be canceled, but unnecessary cancellation signals are generated causing user discomfort
Solution Approach 1:
The patent implements feedback by continuously monitoring the correlation between feedforward and feedback microphone signals and using this information to dynamically control the noise canceling operation. When correlation falls below a threshold indicating no external noise, the system stops generation of cancellation signals, thereby eliminating user discomfort from unnecessary noise canceling while maintaining effectiveness when needed.
Solution Approach 2:
The patent applies dynamics by making the noise canceling system adaptive and controllable based on real-time correlation detection. The system transitions between active and inactive states according to the detected correlation level, allowing it to respond dynamically to changing acoustic environments and avoid generating unnecessary cancellation signals when external noise is absent.
2Object-affected harmful factors
If correlation detection is added to control noise canceling operation, then unnecessary cancellation signals are reduced, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by using the correlation detection mechanism to serve multiple purposes: it controls noise canceling operation, detects presence of external noise, and prevents unnecessary cancellation signal generation. This single correlation monitoring system achieves multiple objectives, reducing overall device complexity compared to implementing separate systems for each function.
Solution Approach 2:
The system performs self-service by using its own internal correlation detection capability to automatically regulate its own operation. The noise canceling system monitors its own effectiveness through correlation between microphones and self-adjusts its behavior, eliminating the need for external control mechanisms or complex additional hardware.
3Measurement precision
If feedback microphone is installed inside NC region, then sound left uncanceled can be detected, but the microphone picks up cancellation signals causing correlation to become negative
Solution Approach 1:
The patent applies preliminary anti-action by anticipating the problem of cancellation signal interference before it affects measurement accuracy. The system uses correlation detection to identify when cancellation signals are present (indicated by negative correlation) and preemptively adjusts or stops noise canceling operation to prevent degradation of measurement precision for detecting uncanceled sound.
Data Source
AI summary
Provided is a signal processing device that performs noise canceling by combining a feedforward method and a feedback method. A signal processing device includes: a correlation calculation unit that calculates a correlation between a first sound pickup signal by a first microphone installed outside a predetermined region and a second sound pickup signal by a second microphone installed in the predetermined region; a determination unit that determines the correlation; and a control unit that performs control based on a result of the determination. The control unit controls execution of signal processing for generating a cancellation signal to be output within the predetermined region from the first sound pickup signal and the second sound pickup signal or output of the cancellation signal.