Vehicular Active Noise Reduction with Split-Band Cabin Audio Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing active noise reduction systems in closed spaces, such as vehicle cabins, face instability in control operations when combining conversation assistance and noise reduction, leading to composite sound output issues and potential howling.
Innovation Solution
An active noise reduction system with dual sound collecting and output units, along with an active noise reduction device that generates composite audio signals to cancel noise, while using transfer function acquisition and correction units to stabilize control operations and prevent howling by setting appropriate gain coefficients and filter coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If simple combination of conversation assisting technology and active noise reduction technology is applied, then both conversation assistance and noise reduction functions are provided, but control stability deteriorates and howling occurs
Solution Approach 1:
The patent divides the audio signal processing into separate channels: a first audio signal for conversation assistance and a second audio signal for noise reduction. The noise reduction device processes these signals independently through separate paths, preventing interference between the two functions and maintaining control stability while providing dual functionality.
Solution Approach 2:
The patent introduces an intermediary processing stage where the noise reduction device generates cancellation sounds based on noise reference signals rather than directly processing the composite conversation audio. This intermediary approach allows noise reduction to be applied without destabilizing the conversation assistance function, eliminating howling while maintaining both functions.
2Object-affected harmful factors
If active noise reduction control is performed based on compounded sound from microphones, then noise reduction is achieved, but control behavior becomes unstable
Solution Approach 1:
The patent extracts the noise reference signal from the compounded audio signal collected by microphones. Instead of using the full composite signal for noise reduction control, the system separates and uses only the noise component as reference, while the conversation assistance signal is processed independently. This extraction prevents the feedback loop from becoming unstable.
Solution Approach 2:
The patent inverts the conventional approach by not using the compounded conversation+noise signal directly for noise reduction control. Instead, it uses the noise reference signal separately, effectively reversing the causal relationship and preventing the feedback instability that occurs when conversation sounds reinforce the noise reduction control loop.
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 effectively stabilizes control operations and ensures both conversation assistance and active noise reduction work correctly, preventing howling and maintaining audio quality.
Implementation Method 1
active noise prediction technology, where cancellation sound having an antiphase as to the phase of the noise is generated from a speaker to reduce invasive noise to the cabin
Implementation Method 2
a first sound collecting unit disposed in a first space in a closed space, that collects sound generated in the first space
Data Source
AI summary
A vehicular active noise reduction system includes a first microphone and first speaker disposed in a front-seat space, a second microphone and second speaker disposed in a back-seat space, and an active noise reduction device that performs control to output cancellation sound, to reduce noise in a cabin, from the first speaker and second speaker. When generating a first composite audio, the active noise reduction device removes audio components belonging to a frequency band relating to a second cancellation sound from audio collected by the first microphone, and when generating a second composite audio, removes audio components belonging to a frequency band relating to a first cancellation sound from audio collected by the second microphone.