Vehicle Audio Coherence-Based Stability Control
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Solution Overview
Problem
Active noise cancellation in vehicles is often unstable due to low coherence between reference and feedback signals, particularly when windows are rolled down, leading to reduced performance and instability in noise cancellation systems.
Innovation Solution
A coherence-based dynamic stability control system that uses a processor to determine coherence between input and output signals, adjusting parameters and output signals dynamically to maintain stability by reducing speaker output or shutting it off when coherence falls below a threshold, and adjusting filter updates accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active noise cancellation is implemented in vehicle audio systems, then noise reduction performance is improved, but system stability deteriorates due to low coherence between reference and feedback signals
Solution Approach 1:
The patent implements a feedback mechanism where coherence between reference and feedback signals is continuously monitored. When coherence exceeds a threshold, the system actively reduces noise; when coherence falls below the threshold, the system detects instability and adjusts accordingly. This feedback loop resolves the contradiction by dynamically responding to coherence conditions, maintaining both noise reduction performance and system stability.
Solution Approach 2:
The patent dynamically adjusts system behavior based on real-time coherence measurements. The controller transitions between different operational states (active noise cancellation vs. stability protection) depending on coherence levels. This dynamic adaptation allows the system to optimize noise reduction when conditions are favorable while preventing instability when coherence degrades, resolving the contradiction between performance and stability.
2Object-affected harmful factors
If noise cancellation signal output is increased to improve noise reduction, then noise reduction performance is improved, but system instability increases when coherence is low
Solution Approach 1:
The patent changes the system parameter (noise cancellation signal output level) based on coherence measurements. When coherence is high, the system increases noise cancellation output for better performance. When coherence is low, the system reduces or shuts off output to maintain stability. This parameter adjustment strategy resolves the contradiction by adapting output levels to coherence conditions.
Solution Approach 2:
The coherence measurement acts as an intermediary that mediates between noise reduction goals and stability requirements. The controller uses coherence as an intermediate indicator to decide whether to increase or decrease noise cancellation output. This intermediary mechanism allows the system to balance performance and stability by responding to the coherence state rather than directly controlling output based on conflicting objectives.
3Reliability
If speaker output is continuously monitored and adjusted based on coherence, then system stability is improved, but device complexity increases
Solution Approach 1:
The patent implements a self-service mechanism where the system automatically monitors its own output and adjusts based on coherence measurements without external intervention. The controller self-regulates noise cancellation output levels based on real-time coherence feedback, eliminating the need for complex external control systems while maintaining stability. This self-service approach resolves the contradiction by providing stable control through relatively simple automatic feedback mechanisms.
Data Source
AI summary
A coherence based dynamic stability control system for a vehicle audio system may include at least one output sensor configured to transmit an output signal including a noise cancellation signal and an undesired noise signal, and at least one input sensor configured to transmit an input signal indicative of an acceleration of a vehicle. A processor may be programmed to control a transducer to output the noise cancellation signal based on at least one parameter, receive the input signal and the output signal, determine a coherence between the input signal and the output signal. The processor may be further programmed to determine whether the coherence exceeds a predefined coherence threshold, adjust the at least one parameter to generate an adjusted parameter and control the transducer to output an updated noise cancellation signal based on the parameter in response to the coherence failing to exceed the predefined coherence threshold.