Active Noise Control Device for Vehicle Passengers
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Solution Overview
Problem
Current active noise control systems in aircraft face limitations in effectively reducing high-frequency noise and spatially adapting to the movement of passengers, particularly due to the short wavelength of high-frequency acoustic waves and the localized effect of counter-noise generation, which results in an inefficient bubble of silence and increased auditory annoyance.
Innovation Solution
A noise processing device with local noise sensors and acoustic actuators positioned on either side of a passenger's head, coupled with a position sensor and processing unit that continuously adapts the transfer functions for counter-noise generation, ensuring effective noise reduction independently of the passenger's head position, and optionally incorporates passive acoustic insulation for enhanced noise filtration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active noise control generates counter-noise for high-frequency noise, then noise attenuation is achieved in localized areas, but the bubble of silence has restricted dimensions and is very localized
Solution Approach 1:
The system divides the noise control task into multiple frequency bands using different control strategies: feed-forward control for low frequencies and feedback control for high frequencies. This segmentation allows each control method to operate in its optimal frequency range, achieving effective noise attenuation across the entire spectrum while maintaining appropriate spatial coverage for each band
Solution Approach 2:
The system transitions from purely spatial control to temporal-spatial control by incorporating adaptive filtering algorithms that process noise signals in the time domain. The use of transfer function estimation and adaptive coefficients allows the system to control noise propagation in addition to spatial distribution, creating effective control zones that adapt to changing acoustic conditions
2Object-affected harmful factors
If passive acoustic treatments are added to isolate occupants from external noise sources, then noise isolation is improved, but the added mass increases
Solution Approach 1:
The system changes the approach from passive physical isolation to active dynamic control by using electronic signal processing and adaptive algorithms. Instead of adding mass through passive materials, the system uses sensors, processors, and actuators to dynamically generate counter-noise signals that adapt to changing noise conditions, achieving noise isolation without significant weight increase
Solution Approach 2:
The system replaces mechanical passive isolation structures with an electro-acoustic active control system. Rather than relying on physical barriers and absorbing materials, the system uses electronic sensing, digital signal processing, and electro-acoustic transducers to actively cancel noise, substituting a mechanical approach with an electrical and computational approach that has minimal added mass
3Object-affected harmful factors
If retroactive techniques are used to compensate for noise variations after their appearance, then noise control is achieved, but the response time increases
Solution Approach 1:
The system implements feed-forward control that uses a reference noise signal to predict and prepare counter-noise before the primary noise actually reaches the control zone. By anticipating noise variations through the reference signal and transfer function estimation, the system generates compensating signals in advance, reducing the effective response time and preventing noise from fully developing in the controlled area
Solution Approach 2:
The system employs feedback control using error sensors to continuously monitor the actual noise level in the control zone and adjust the counter-noise generation in real-time. This closed-loop feedback mechanism allows the system to respond to actual noise conditions with minimal delay, continuously optimizing the control signal to maintain effective noise attenuation despite varying environmental conditions
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 system generates a mobile bubble of silence effectively targeted at the passenger's ears, reducing high-frequency noise annoyance and maintaining noise reduction regardless of head movement, while also optimizing noise filtration across a range of frequencies.
Implementation Method 1
active control methods aim to generate counter-noise to induce a bubble of silence
Implementation Method 2
A local noise measurement device aims to determine the noise resulting from the combination of secondary and primary noise
Implementation Method 3
Depending on the local noise measured, the processing unit then adapts the coefficients of the filter produced by the algorithm used
Data Source
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AI summary
The device has a position sensor determining a position of a head of a passenger. A treatment unit is connected to a local noise sound sensor to receive a local noise signal, and delivers a control signal to a sound actuator, where the control signal is function of the local noise signal and transfer function per ear and relates to transferring sound waves between a sound actuator and the passenger. An active matching unit co-operates with the sensor to keep the transfer function used in preparing the control signal representative of a path traveled by anti-noise. An independent claim is also included for a method for attenuating noise on a board in a vehicle.