Dynamic Microphone Mixing for Smooth Speaker Switching Noise
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Solution Overview
Problem
Existing multi-microphone systems fail to effectively combine signals from different speakers in noisy environments, particularly in scenarios like car telephony, where varying background noise and speech levels lead to noticeable noise jumps and increased noise levels during speaker switching.
Innovation Solution
A dynamic signal mixer system that uses spectral preprocessing to equalize signal-to-noise ratios and noise characteristics across channels, employing a noise reduction algorithm and automatic gain control to adjust signal levels and attenuate background noise based on noise power spectral density and voice activity detection, ensuring smooth transitions between speakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hard switching between active speakers is done, then speaker changes are rapid, but noise jumps and coloration become noticeable
Solution Approach 1:
The patent implements dynamic mixing ratios that continuously adapt based on voice activity detection and noise level analysis. Instead of fixed hard switching, the system dynamically adjusts the contribution of each microphone signal to the output, allowing smooth transitions that prevent noticeable noise jumps while maintaining rapid speaker changes.
Solution Approach 2:
The system changes the mixing parameter (mixing ratio) dynamically based on detected voice activity and noise characteristics. By adjusting the weight of each microphone signal according to real-time conditions, the system achieves both rapid speaker switching and smooth noise transitions without audible artifacts.
2Stability of the object's composition
If soft mixing functions are used, then speaker transitions are smooth, but the resulting noise level increases
Solution Approach 1:
The patent applies different processing to different frequency bands and time segments. By analyzing noise characteristics locally in time and frequency domains, the system can apply aggressive noise reduction where needed while maintaining smooth mixing where speech is present, thus achieving both transition smoothness and noise control.
Solution Approach 2:
The system performs preliminary noise characterization and voice activity detection before mixing occurs. By pre-identifying noise components and speech segments, the system can pre-calculate optimal mixing ratios that ensure smooth transitions without incorporating excessive noise from inactive microphones.
3Manufacturing precision
If spectral preprocessing is applied, then noise characteristics are equalized, but processing complexity increases
Solution Approach 1:
The patent divides the signal processing into distinct stages: voice activity detection, noise level estimation, spectral preprocessing, and mixing ratio calculation. By segmenting the complex processing task into modular stages, the system achieves precise noise equalization while making the overall complexity manageable through organized processing steps.
Data Source
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AI summary
A system and method of signal combining that supports different speakers in a noisy environment is provided. Particularly for deviations in the noise characteristics among the channels, various embodiments ensure a smooth transition of the background noise at speaker changes. A modified noise reduction (NR) may achieve equivalent background noise characteristics for all channels by applying a dynamic, channel specific, and frequency dependent maximum attenuation. The reference characteristics for adjusting the background noise may be specified by the dominant speaker channel. In various embodiments, an automatic gain control (AGC) with a dynamic target level may ensure similar speech signal levels in all channels.