Christophe Ris

Learn More
The results of our research presented in this paper are two-fold. First, an estimation of global posteriors is formalized in the framework of hybrid HMM/ANN systems. It is shown that hybrid HMM/ANN systems, in which the ANN part estimates local posteriors, can be used to modelize global model posteriors. This formalization provides us with a clear theory in(More)
Major progress is being recorded regularly on both the technology and exploitation of automatic speech recognition (ASR) and spoken language systems. However, there are still technological barriers to flexible solutions and user satisfaction under some circumstances. This is related to several factors, such as the sensitivity to the environment (background(More)
In this paper, we propose a new acoustic confidence measure of ASR hypothesis and compare it to approaches proposed in the literature. This approach takes into account prior information on the acoustic model performance specific to each phoneme. The new method is tested on two types of recognition errors: the out-of-vocabulary words and the errors due to(More)
The paper proposes a solution that brings some advances to the genericity of the ASR technology towards tasks and languages. A non-linear discriminant model is built from multi-lingual, multi-task speech material in order to classify the acoustic signal into language independent phonetic units. Instead of considering this model for direct HMM state(More)
In this paper, we discuss the use of artificial room reverberation to increase the performance of automatic speech recognition (ASR) systems in reverberant enclosures. Our approach consists in training acoustic models on artificially reverberated speech material. In order to obtain the desired reverberated speech training database, we propose to use a(More)
This paper briefly reviews state of the art related to the topic of speech variability sources in automatic speech recognition systems. It focuses on some variations within the speech signal that make the ASR task difficult. The variations detailed in the paper are intrinsic to the speech and affect the different levels of the ASR processing chain. For(More)