Adaptive Gain Control for Stable In-Car Speech Intelligibility
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Solution Overview
Problem
Conventional in-car communication systems face challenges in providing a consistent audio impression due to varying noise levels and speaker-dependent speech volumes, leading to acoustic loss and discomfort for passengers.
Innovation Solution
A communication system that combines automatic gain control (AGC) and noise-dependent gain control (NDGC) with loss control, using psychoacoustic measures to maintain a target Signal-To-Noise Ratio (SNR) and adapt gain levels dynamically, ensuring a natural and stable audio experience across different environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional systems use fixed gain control, then the system structure is simple, but the audio impression varies with noise levels and speaker volumes
Solution Approach 1:
The patent implements dynamic gain control by continuously adapting the gain value based on real-time speech and noise level measurements. The system transitions from fixed gain to variable gain that automatically adjusts to maintain consistent audio impression across different acoustic conditions and speaker volumes
Solution Approach 2:
The system uses feedback mechanisms by measuring the actual speech and noise levels, comparing them against target values, and adjusting the gain accordingly. This closed-loop control ensures the audio impression remains stable despite variations in speaker-dependent volumes and environmental noise
2Adaptability or versatility
If the system adapts gain for each speaker, then audio quality improves, but tuning effort increases
Solution Approach 1:
The system performs self-adjustment by automatically measuring each speaker's voice characteristics and noise environment, then computing the appropriate gain values without requiring manual tuning. The adaptive algorithm autonomously optimizes the audio impression for each speaker, eliminating the need for extensive manual calibration
Solution Approach 2:
The system dynamically changes the gain parameter based on measured speech and noise levels for each speaker. By automatically adapting the gain parameter to match individual speaker characteristics and environmental conditions, the system achieves speaker-specific optimization without manual intervention
3Measurement precision
If the system increases gain in noisy environments, then speech intelligibility improves, but natural audio impression may be compromised
Solution Approach 1:
The system selectively changes gain parameters across different frequency bands rather than applying uniform gain adjustment. By modifying specific frequency components where speech information is concentrated while preserving other frequency regions, the system enhances speech intelligibility in noisy environments while maintaining the natural characteristics of the audio signal
Data Source
AI summary
Methods and apparatus for a communication system having microphones and loudspeakers to determine a noise and speech level estimate for a transformed signal, determine a SNR from the noise and speech level estimates, and determine a gain for the transformed signal to achieve a selected SNR range at a given position. In one embodiment, the gain is determined by adapting an actual gain to follow a target gain, wherein the target gain is adjusted to achieve the selected SNR range.