Microphone Placement for Vehicle Noise Attenuation
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Solution Overview
Problem
Existing noise cancellation systems in vehicles fail to effectively attenuate noise at specific frequencies and locations within the passenger compartment, as they do not accurately replicate the acoustic characteristics experienced by the occupant, leading to incomplete noise reduction.
Innovation Solution
A method and system that strategically places one or more microphones, including virtual microphones formed by combining multiple microphones, at locations within the vehicle where the acoustic transfer functions match those experienced by the occupant, allowing for the generation of noise-canceling audio signals that attenuate specific frequencies detected by the microphone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microphones are placed at arbitrary locations in the passenger compartment, then the system structure is simple, but the noise cancellation effectiveness is poor because the acoustic characteristics do not match those at the occupant's ear
Solution Approach 1:
The patent performs preliminary acoustic measurements to identify locations where the transfer function matches the occupant's ear characteristics before deploying the noise cancellation system. This pre-positioning ensures that microphones are placed at optimal locations that replicate the acoustic environment at the occupant's ear, thereby improving noise cancellation effectiveness without requiring complex real-time adjustments during operation
Solution Approach 2:
The patent creates a virtual copy of the acoustic environment at the occupant's ear by placing microphones at locations where the transfer function from speakers to microphone matches the transfer function from speakers to the occupant's ear. This copying approach allows the system to replicate the acoustic characteristics experienced by the occupant, enabling effective noise cancellation without directly measuring at the ear itself
2Measurement precision
If multiple microphones are combined to form virtual microphones, then the acoustic characteristic matching is improved, but the system complexity and computational requirements increase
Solution Approach 1:
The patent combines signals from multiple physical microphones to create virtual microphones that replicate the acoustic characteristics at the occupant's ear. By merging the outputs of multiple microphones with different transfer functions, the system can synthesize a virtual microphone response that closely matches the target acoustic environment, thereby improving measurement precision while distributing the complexity across multiple simpler components
Solution Approach 2:
The virtual microphone system serves multiple functions: it can replicate acoustic characteristics at different locations, adapt to different speaker configurations, and provide flexible positioning without physical constraints. This multi-functionality allows a single virtual microphone implementation to handle various acoustic scenarios, reducing the need for multiple specialized physical microphones and thereby managing complexity through versatility
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 approach achieves noticeable noise reduction by ensuring that the noise-canceling audio signals effectively counteract the ambient noise, providing a quieter environment for the occupant by matching the acoustic characteristics of sound at the microphone's location to that at the occupant's ear, thereby enhancing noise cancellation efficiency.
Implementation Method 1
sound emitted from one or more speakers has acoustic characteristics that are substantially similar in measure to corresponding acoustic characteristics of the emitted sound at a location near an ear
Implementation Method 2
a noise-canceling audio signal is generated to attenuate one or more frequencies in the sound detected by the microphone
Data Source
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AI summary
A method and system for attenuating noise comprises identifying a location in an area at which sound emitted from one or more speakers has acoustic characteristics that are substantially similar in measure to corresponding acoustic characteristics of the emitted sound at a location approximated to be near an ear of an occupant of the area. A microphone, which may be a virtual microphone, is disposed at the identified location. The microphone detects sound at the identified location. In response to the sound detected by the microphone, the one or more speakers emit a noise-canceling audio signal adapted to attenuate one or more frequencies in the sound detected by the microphone.