In-Vehicle Signal Processing for Acoustic Feedback Control
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Solution Overview
Problem
In-vehicle communication systems and hands-free telephony sets face challenges in maintaining speech signal quality due to acoustic feedback and noise, particularly in passenger compartments where background noise and reverberation complicate echo compensation, leading to reduced intelligibility and potential communication breakdowns.
Innovation Solution
A signal processing system that integrates microphones, loudspeakers, hands-free telephony, and in-vehicle communication systems, using adaptive echo compensation filtering and amplification control based on speech activity detection in telephone signals to reduce echoes and noise, with the hands-free set and in-vehicle communication system sharing electronic and logic components to optimize signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the in-vehicle communication system amplifies microphone signals for clear passenger communication, then speech intelligibility between passengers is improved, but acoustic feedback and echoes increase due to loudspeaker-microphone coupling in the confined space
Solution Approach 1:
The patent implements an adaptive feedback mechanism where the hands-free set detects speech activity in telephone signals and dynamically controls the amplification gain of the in-vehicle communication system. When speech is detected in the telephone signal, the system reduces amplification to prevent acoustic feedback, while maintaining sufficient gain for clear passenger communication during non-speech periods
Solution Approach 2:
The system dynamically adjusts the amplification characteristics of the in-vehicle communication system based on real-time detection of speech activity in telephone signals. The amplification factor is varied adaptively rather than remaining constant, allowing the system to optimize between speech intelligibility and acoustic feedback prevention depending on current operating conditions
2Device complexity
If the hands-free set and in-vehicle communication system operate simultaneously with shared microphones and loudspeakers, then device complexity is reduced, but echo compensation fails due to rapidly changing echo paths
Solution Approach 1:
The patent segments the echo compensation function into two distinct systems with different responsibilities: the in-vehicle communication system handles echo compensation for passenger-to-passenger communication, while the hands-free set handles echo compensation for telephone communication. This segmentation allows each system to optimize its echo compensation algorithm for its specific communication mode, maintaining reliability despite shared hardware
Solution Approach 2:
The patent introduces speech activity detection as an intermediary control mechanism that coordinates between the hands-free set and in-vehicle communication system. The detection of speech activity in telephone signals serves as a mediator signal that triggers adaptive control actions, enabling both systems to operate simultaneously without interfering with each other's echo compensation performance
3Measurement precision
If amplification is increased to overcome background noise in the passenger compartment, then speech signal clarity is improved, but noise and feedback from loudspeakers are also amplified
Solution Approach 1:
The system dynamically adjusts amplification based on speech activity detection rather than using fixed high gain. During active speech periods, amplification is increased to ensure clarity; during non-speech periods or when telephone speech is detected, amplification is reduced to minimize noise and feedback, creating an adaptive noise management strategy
Data Source
AI summary
The present invention relates to a signal processing system, comprising a number of microphones and loudspeakers, a hands-free set configured to receive a telephone signal from a remote party and to transmit a microphone signal supplied by at least one of the microphones to the remote party; an in-vehicle communication system configured to receive a microphone signal supplied by at least one of the microphones; receive the telephone signal; amplify the microphone signal to obtain at least one first output signal; output the at least one first output signal and/or a second output signal corresponding to the telephone signal to at least one of the loudspeakers; and wherein the signal processing systems is configured to detect speech activity in the telephone signal and to control the in-vehicle communication system to reduce amplification of the microphone signal by a damping factor, if it is detected that speech activity is present in the telephone signal.