Robust Speech Detection for Noisy Environments

This paper presents a robust voice activity detector (VAD) based on hidden Markov models (HMM) to improve speech recognition systems in stationary and non-stationary noise environments: inside motor vehicles (like cars or planes) or inside buildings close to high traffic places (like in a control tower for air traffic control (ATC)). In these environments, there is a high stationary noise level caused by vehicle motors and additionally, there could be people speaking at certain distance from the main speaker producing non-stationary noise. The VAD presented in this paper is characterized by a new front-end and a noise level adaptation process that increases significantly the VAD robustness for different signal to noise ratios (SNRs). The feature vector used by the VAD includes the most relevant Mel Frequency Cepstral Coefficients (MFCC), normalized log energy and delta log energy. The proposed VAD has been evaluated and compared to other well-known VADs using three databases containing different noise conditions: speech in clean environments (SNRs mayor que 20 dB), speech recorded in stationary noise environments (inside or close to motor vehicles), and finally, speech in non stationary environments (including noise from bars, television and far-field speakers). In the three cases, the detection error obtained with the proposed VAD is the lowest for all SNRs compared to Acero¿s VAD (reference of this work) and other well-known VADs like AMR, AURORA or G729 annex b

An Automatic Real-time Synchronization of Live speech with Its Transcription Approach

Most studies in automatic synchronization of speech and transcription focus on the synchronization at the sentence level or the phrase level. Nevertheless, in some languages, like Thai, boundaries of such levels are difficult to linguistically define, especially in case of the synchronization of speech and its transcription. Consequently, the synchronization at a finer level like the syllabic level is promising. In this article, an approach to synchronize live speech with its corresponding transcription in real time at the syllabic level is proposed. Our approach employs the modified real-time syllable detection procedure from our previous work and the transcription verification procedure then adopts to verify correctness and to recover errors caused by the real-time syllable detection procedure. In experiments, the acoustic features and the parameters are customized empirically. Results are compared with two baselines which have been applied to the Thai scenario. Experimental results indicate that, our approach outperforms two baselines with error rate reduction of 75.9% and 41.9% respectively and also can provide results in the real-time situation. Besides, our approach is applied to the practical application, namely ChulaDAISY. Practical experiments show that ChulaDAISY applied with our approach could reduce time consumption for producing audio books