Dual-Microphone Voice Activity Detection Technique Based on Two-Step Power Level Difference Ratio

In this paper, we propose a novel dual-microphone voice activity detection (VAD) technique based on the two-step power level difference (PLD) ratio. This technique basically exploits the PLD between the primary microphone and the secondary microphone in a mobile device when the distance between the microphones and the sound source is relatively short. Based on the PLD, we propose the use of the PLD ratio (PLDR) instead of the original PLD to take advantage of the relative difference between the PLD of speech and the PLD of noise. Indeed, the PLDR is obtained by estimating the ratio of the PLD between the input signals and the PLD between the two channel noises during periods without speech. The proposed technique offers a two-step algorithm using the PLDRs including long-term PLDR (LT-PLDR), which characterizes long-term evolution and short-term PLDR (ST-PLDR), which characterizes short-time variation during the first step. LT-PLDR-based and ST-PLDR-based VAD decision are performed using the maximum a posteriori (MAP) probability derived from the model-trust algorithm and combined at the second step to reach a superior VAD decision for both long-term and short-term situations. Extensive experimental results show that the proposed dual-microphone VAD technique outperforms the conventional two-channel VAD method as well as most standardized VAD algorithms.