Bing Xiang

Morphological Decomposition for Arabic Broadcast News Transcription

In this paper, we present a novel approach for morphological decomposition in large vocabulary Arabic speech recognition. It achieved low out-of-vocabulary (OOV) rate as well as high recognition accuracy in a state-of-the-art Arabic broadcast news transcription system. In this approach, the compound words are decomposed into stems and affixes in both language training and acoustic training data. The decomposed words in the recognition output are re-joined before scoring. Four algorithms are experimented and compared in this work. The best system achieved 1.9% absolute reduction (9.8% relative) in word error rate (WER) when compared to the 64K-word baseline. The recognition performance of this system is also comparable to a 300K-word recognition system trained on the normal words. In the meantime, the decomposed system is much faster in terms of speed and also needs less memory than the systems with larger than 64K vocabularies

Advances in transcription of broadcast news and conversational telephone speech within the combined EARS BBN/LIMSI system

This paper describes the progress made in the transcription of broadcast news (BN) and conversational telephone speech (CTS) within the combined BBN/LIMSI system from May 2002 to September 2004. During that period, BBN and LIMSI collaborated in an effort to produce significant reductions in the word error rate (WER), as directed by the aggressive goals of the Effective, Affordable, Reusable, Speech-to-text [Defense Advanced Research Projects Agency (DARPA) EARS] program. The paper focuses on general modeling techniques that led to recognition accuracy improvements, as well as engineering approaches that enabled efficient use of large amounts of training data and fast decoding architectures. Special attention is given on efforts to integrate components of the BBN and LIMSI systems, discussing the tradeoff between speed and accuracy for various system combination strategies. Results on the EARS progress test sets show that the combined BBN/LIMSI system achieved relative reductions of 47% and 51% on the BN and CTS domains, respectively

Speech recognition in multiple languages and domains: the 2003 BBN/LIMSI EARS system

We report on the results of the first evaluations for the BBN/LIMSI system under the new DARPA EARS program. The evaluations were carried out for conversational telephone speech (CTS) and broadcast news (BN) for three languages: English, Mandarin, and Arabic. In addition to providing system descriptions and evaluation results, the paper highlights methods that worked well across the two domains and those few that worked well on one domain but not the other. For the BN evaluations, which had to be run under 10 times real-time, we demonstrated that a joint BBN/LIMSI system with a time constraint achieved better results than either system alone.

Integrating Speech Recognition and Machine Translation

This paper presents a set of experiments that we conducted in order to optimize the performance of an Arabic/English machine translation system on broadcast news and conversational speech data. Proper integration of speech-to-text (STT) and machine translation (MT) requires special attention to issues such as sentence boundary detection, punctuation, STT accuracy, tokenization, conversion of spoken numbers and dates to written form, optimization of MT decoding weights, and scoring. We discuss these issues, and show that a carefully tuned STT/MT integration can lead to significant translation accuracy improvements compared to simply feeding the regular STT output to a text MT system.

Cluster-dependent acoustic modeling [speech recognition applications]

In this paper, we present cluster-dependent acoustic modeling for large-vocabulary speech recognition. With large amounts of acoustic training data, we build multiple cluster-dependent models (CDM), each focusing on a group of speakers in order to represent speaker-dependent characteristics. It is motivated by the fact that a sufficiently trained speaker-dependent (SD) model is better than the speaker-independent (SI) model. During decoding, we decode the data of each test speaker using CDMs selected under certain criteria to achieve high recognition accuracy. Various speaker clustering and model selection techniques are proposed and compared in the task of broadcast news (BN) transcription. The CDM provided more than 1% absolute gain in unadapted decoding and 0.5% gain in adapted decoding when compared to our baseline system on the EARS BN 2003 development test set.