In-Car Loudspeaker Noise Suppression for Clearer Passenger Speech
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Solution Overview
Problem
Existing in-car communication systems fail to adequately suppress noise, leading to either imperceptible noise or speech degradation, as they do not adjust noise suppression based on varying ambient noise levels across different listening positions within a vehicle.
Innovation Solution
A sound collection and amplification apparatus that estimates noise levels at multiple positions, sets appropriate noise suppression amounts to minimize perceived noise while maintaining speech quality, by using noise level estimating and suppression amount setting components to adjust noise suppression dynamically based on the ambient noise conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise suppression amount is increased to reduce noisy sound from speaker, then noise output from speaker is reduced, but speech degradation occurs
Solution Approach 1:
The noise suppression amount is made dynamic rather than fixed. The system calculates the noise suppression amount based on real-time noise levels at both the microphone and speaker positions, allowing the suppression level to adapt continuously to changing acoustic conditions. This resolves the contradiction by enabling the system to apply stronger suppression when noise is high and weaker suppression when noise is low, preventing both excessive noise output and speech degradation.
Solution Approach 2:
The system changes the parameter of noise suppression amount based on measured noise levels. By calculating the ratio between noise at the microphone position and noise at the speaker position, the system dynamically adjusts the suppression parameter to achieve optimal noise reduction while preserving speech quality. This parameter adaptation allows the system to navigate the trade-off between noise reduction and speech preservation.
2Object-affected harmful factors
If noise suppression is applied to reduce noisy sound, then noise from speaker is reduced, but speech quality degrades when ambient noise is small
Solution Approach 1:
The noise suppression parameter is changed dynamically based on the ambient noise level. When ambient noise is small, the system calculates a smaller suppression amount to preserve speech quality. When ambient noise is large, the system applies stronger suppression. This parameter adaptation ensures that speech quality is maintained in quiet environments while still achieving noise reduction in noisy environments.
Solution Approach 2:
The system uses feedback from noise level measurements at both microphone and speaker positions to adjust the suppression amount. By continuously monitoring the acoustic environment and adjusting suppression based on the measured noise ratio, the system can maintain speech quality while reducing noise output. This feedback mechanism prevents over-suppression in quiet conditions.
3Device complexity
If fixed noise suppression amount is used, then system complexity is reduced, but noise suppression effectiveness varies across different listening positions
Solution Approach 1:
The system segments the noise measurement process by placing measurements at different positions (microphone position and speaker position). By measuring noise levels separately at these two locations and calculating the ratio, the system achieves position-adaptive noise suppression without requiring complex multi-zone control. This segmentation approach enables effective noise suppression for different listening positions while maintaining relatively simple system architecture.
Data Source
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AI summary
A first noise level, which is an estimated value of a magnitude of a noise component included in a first sound collection signal obtained from a first microphone which collects sound emitted from a first sound collection and amplification position is obtained, a second noise level, which is an estimated value of a magnitude of a noise component included in a second sound collection signal obtained from a second microphone which collects sound emitted from a second sound collection and amplification position is obtained, a ratio of a reproduced noisy sound level, which is an estimated value of a magnitude of noise at a position of a passenger at the second sound collection and amplification position in a case where the first noise level is reproduced from a second speaker placed at the second sound collection and amplification position, with respect to a second noisy sound level, which is an estimated value of a magnitude of noise corresponding to the second noise level at the position of the passenger at the second sound collection and amplification position is obtained, and a noise suppression amount is obtained so that a product of this ratio and the noise suppression amount becomes a constant set in advance.