Multi-Input Feature Combination in the Cepstral Domain for Practical Speech Recognition Systems

Yasunari OBUCHI  Nobuo HATAOKA  

IEICE TRANSACTIONS on Information and Systems   Vol.E92-D   No.4   pp.662-670
Publication Date: 2009/04/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.E92.D.662
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Speech and Hearing
robust speech recognition,  microphone array,  MFCC,  feature combination,  HMM,  

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In this paper we describe a new framework of feature combination in the cepstral domain for multi-input robust speech recognition. The general framework of working in the cepstral domain has various advantages over working in the time or hypothesis domain. It is stable, easy to maintain, and less expensive because it does not require precise calibration. It is also easy to configure in a complex speech recognition system. However, it is not straightforward to improve the recognition performance by increasing the number of inputs, and we introduce the concept of variance re-scaling to compensate the negative effect of averaging several input features. Finally, we propose to take another advantage of working in the cepstral domain. The speech can be modeled using hidden Markov models, and the model can be used as prior knowledge. This approach is formulated as a new algorithm, referred to as Hypothesis-Based Feature Combination. The effectiveness of various algorithms are evaluated using two sets of speech databases. We also refer to automatic optimization of some parameters in the proposed algorithms.