Seat-Adaptive Active Noise Reduction via Shifted Impulse Response
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Solution Overview
Problem
Existing active noise reduction devices struggle to effectively reduce noise when the position or orientation of a microphone in a mobile object, such as a vehicle seat, is adjusted, as they rely on fixed sound transfer characteristics that do not account for changes in the seat's configuration.
Innovation Solution
An active noise reduction device that includes an adaptive filter system with a simulated sound transfer characteristic generator, which adjusts the impulse response based on the seat's position and orientation, using downsampling and upsampling to generate a cancellation signal that optimizes noise reduction performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed sound transfer characteristic is used for active noise reduction, then the device complexity is reduced, but the noise reduction performance deteriorates when the seat position or orientation changes
Solution Approach 1:
The patent implements dynamic adaptation of the sound transfer characteristic by detecting seat position and orientation changes, then adjusting the impulse response accordingly. This transforms the fixed characteristic system into a dynamic one that automatically adapts to changing conditions, resolving the contradiction between simplicity and performance.
Solution Approach 2:
The patent changes the parameters of the sound transfer characteristic (impulse response) based on detected seat adjustments. By modifying the temporal and spatial parameters of the impulse response to match the new seat configuration, the system maintains optimal noise reduction performance without requiring complete recalibration.
2Reliability
If the impulse response is adjusted for each seat position change, then the noise reduction performance is improved, but the processing time and computational load increase
Solution Approach 1:
The patent performs preliminary measurements of sound transfer characteristics at various predetermined seat positions and stores these as pre-computed impulse responses. When the seat position changes, the system simply selects or interpolates between pre-computed values rather than performing real-time measurements, significantly reducing processing time while maintaining performance.
Solution Approach 2:
The patent creates copies of the impulse response for different seat configurations through pre-measurement and storage. Instead of recalculating the sound transfer characteristic from scratch for each position change, the system uses pre-prepared copies that can be quickly applied, reducing computational burden while maintaining accuracy.
3Productivity
If the sampling rate is reduced through downsampling, then the processing efficiency is improved, but the sound transfer characteristic accuracy may deteriorate
Solution Approach 1:
The patent carefully manages the sampling rate parameter by downsampling the impulse response to a lower rate suitable for the active noise reduction processing. This parameter change reduces computational complexity while the downsampling is performed in a way that preserves the essential characteristics of the sound transfer function, balancing efficiency and accuracy.
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
The device improves noise reduction performance by generating a cancellation signal that adapts to seat adjustments, ensuring effective noise control even when the microphone's position or orientation changes, thereby enhancing stability and efficiency.
Implementation Method 1
an active noise reduction device that actively reduces noise by outputting a cancellation sound for cancelling noise from a cancellation sound source by using a reference signal that correlates with the noise and an error signal that is based on a residual sound obtained by interference between the noise and the cancellation sound
Data Source
AI summary
An active noise reduction device includes a storage that stores an impulse response with a first sampling rate, the impulse response simulating a sound transfer characteristic ranging from a loudspeaker to a microphone when the adjustment state of a seat is a reference position, and a simulated sound transfer characteristic generator that generates a simulated sound transfer characteristic by acquiring the adjustment state of the seat, shifting the impulse response in a time-base direction according to the acquired adjustment state of the seat, and downsampling the shifted impulse response from the first sampling rate to a second sampling rate.