Stability Control in a Two-Channel Speech Reinforcement System for Vehicles

This paper presents a two-channel speech reinforcement system for cars able to improve the communication between the front and the rear passengers. One of the problems of this kind of systems is that they must operate in closed-loop, as acoustic feedback paths appear due to the short distance between loudspeakers and microphones. This feedback paths can make the system become unstable and acoustic echo control is needed in order to ensure stability. The system must perform two plant identifications for each channel. One of them is an open-loop identification and the other one is closed-loop. We propose here the use of echo suppression filters specially designed for closed-loop subsystems along with echo suppression filters for open-loop subsystems based on the optimal filtering theory. Results about the performance of the proposed system are provided