Active Noise Reduction Head Position Adaptation
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Solution Overview
Problem
Conventional active noise reduction systems are limited in their noise reduction effectiveness to specific areas around the error detector, such as a microphone, and fail to adequately reduce noise when the occupant's head position changes.
Innovation Solution
An active noise reduction system that includes a reference signal generator, a canceling sound output device, an error detector, a reference distance detector, and a controller. The controller generates a first canceling estimation signal based on the reference signal and adjusts its time delay and amplitude to create a second canceling estimation signal tailored to the occupant's head position, allowing the control filter to be updated accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the error detector (microphone) is used to detect noise for active noise reduction, then the noise reduction effect is achieved in the area around the error detector, but the noise reduction effectiveness is limited to a specific area and cannot adequately reduce noise when the occupant's head position changes
Solution Approach 1:
The patent introduces a reference distance detector as an intermediary device that measures the distance between the occupant's head and the canceling sound output device. This additional measurement enables the controller to adjust the control filter based on actual head position, bridging the gap between the fixed error detector and the moving head position to maintain effective noise reduction across different positions.
2Reliability
If a control filter is updated based on the error signal from the error detector, then the noise reduction control is achieved, but the calculation load increases when trying to account for occupant head position changes
Solution Approach 1:
The patent changes the approach by using the reference distance measurement to directly adjust key parameters (time delay and amplitude) of the control filter based on head position, rather than performing full recalculation of the control filter. This parameter-based adjustment reduces the computational burden while maintaining control accuracy adapted to head position changes.
3Reliability
If the control filter is adjusted to follow head position changes, then noise reduction effectiveness at the head position is maintained, but the system complexity and cost increase
Solution Approach 1:
The patent implements preliminary action by having the reference distance detector continuously measure and provide head position information to the controller. This advance knowledge of head position allows the controller to proactively adjust the control filter parameters before the occupant moves out of the effective noise reduction zone, maintaining effectiveness without requiring complex real-time tracking systems.
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 solution enables effective noise reduction at the occupant's head position even when the head position changes, while also reducing the calculation load of the controller and allowing for a more inexpensive processor to be used.
Implementation Method 1
an active noise reduction system that reduces a noise by causing a canceling sound in an opposite phase to the noise to interfere with the noise
Data Source
AI summary
An active noise reduction system reduces a noise in an internal space of a mobile body. The active noise reduction system includes a controller configured to control a canceling sound output device. The controller is configured to generate a first canceling estimation signal as an estimation signal of a canceling sound at a position of an error detector based on a reference signal, generate a second canceling estimation signal as an estimation signal of the canceling sound at a head position of an occupant by adjusting a time delay and an amplitude of the first canceling estimation signal based on a reference distance, and update a control filter for controlling the canceling sound output device based on the second canceling estimation signal.