ROBUSTNESS IMPROVEMENT OF ULTRASOUND-BASED SENSOR SYSTEMS FOR SPEECH COMMUNICATION

In recent years, auxiliary sensors have been employed to improve the robustness of emerging hands-free speech communication systems based on air-conduction microphones, especially in low signal-to-noise-ratio environments. One such sensor, based on ultrasound, captures articulatory movement information during speech production and has been used in a voice activity detector and also shown to improve the performance of speech recognizers. However, studies thus far have tested such sensors in ideal scenarios where only relevant articulatory information was assumed to he present. Therefore, in this paper the robustness of such sensors in realistic scenarios is investigated. Challenges arising from non-articulatory movements and other environmental influences captured by ultrasound sensors are discussed and strategies for their detection presented. Finally, the proposed strategies are evaluated in an ultrasound-based voice activity detector.