Improving ASR error detection with non-decoder based features

Abstract This study reports error detection experiments in large vocabulary automatic speech recognition (ASR) systems, by using statistical classifiers. We explored new features gathered from other knowledge sources than the decoder itself: a binary feature that compares outputs from two different ASR systems (word by word), a feature based on the number of hits of the hypothesized bigrams, obtained by queries entered into a very popular Web search engine, and finally a feature related to automatically infered topics at sentence and word levels. Experiments were conducted on a European Portuguese broadcast news corpus. The combination of baseline decoder-based features and two of these additional features led to significant improvements, from 13.87% to 12.16% classification error rate (CER) with a maximum entropy model, and from 14.01% to 12.39% CER with linear-chain conditional random fields, comparing to a baseline using only decoder-based features

“CAN YOU GIVE ME ANOTHER WORD FOR HYPERBARIC?”: IMPROVING SPEECH TRANSLATION USING TARGETED CLARIFICATION QUESTIONS

We present a novel approach for improving communication success between users of speech-to-speech translation systems by automatically detecting errors in the output of automatic speech recognition (ASR) and statistical machine translation (SMT) systems. Our approach initiates system-driven targeted clarification about errorful regions in user input and repairs them given user responses. Our system has been evaluated by unbiased subjects in live mode, and results show improved success of communication between users of the system. Index Terms — Speech translation, error detection, error correction, spoken dialog systems. 1

USER-AWARENESS AND ADAPTATION IN CONVERSATIONAL AGENTS

This paper considers the research question of developing user-aware and adaptive conversational agents. The conversational agent is a system which is user-aware to the extent that it recognizes the user identity and his/her emotional states that are relevant in a given interaction domain. The conversational agent is user-adaptive to the extent that it dynamically adapts its dialogue behavior according to the user and his/her emotional state. The paper summarizes some aspects of our previous work and presents work-in-progress in the field of speech-based human-machine interaction. It focuses particularly on the development of speech recognition modules in cooperation with both modules for emotion recognition and speaker recognition, as well as the dialogue management module. Finally, it proposes an architecture of a conversational agent that integrates those modules and improves each of them based on some kind of synergies among themselves

The Prosody of Uncertainty for Spoken Dialogue Intelligent Tutoring Systems

The speech medium is more than an audio conveyance of word strings. It contains meta information about the content of the speech. The prosody of speech, pauses and intonation, adds an extra dimension of diagnostic information about the quality of a speaker\u27s answers, suggesting an important avenue of research for spoken dialogue tutoring systems. Tutoring systems that are sensitive to such cues may employ different tutoring strategies based on detected student uncertainty, and they may be able to perform more precise assessment of the area of student difficulty. However, properly identifying the cues can be challenging, typically requiring thousands of hand labeled utterances for training in machine learning. This study proposes and explores means of exploiting alternate automatically generated information, utterance correctness and the amount of practice a student has had, as indicators of student uncertainty. It finds correlations with various prosodic features and these automatic indicators and compares the result with a small set of annotated utterances, and finally demonstrates a Bayesian classifier based on correctness scores as class labels

Using Open-Source Automatic Speech Recognition Tools for the Annotation of Dutch Infant-Directed Speech

There is a large interest in the annotation of speech addressed to infants. Infant-directed speech (IDS) has acoustic properties that might pose a challenge to automatic speech recognition (ASR) tools developed for adult-directed speech (ADS). While ASR tools could potentially speed up the annotation process, their effectiveness on this speech register is currently unknown. In this study, we assessed to what extent open-source ASR tools can successfully transcribe IDS. We used speech data from 21 Dutch mothers reading picture books containing target words to their 18- and 24-month-old children (IDS) and the experimenter (ADS). In Experiment 1, we examined how the ASR tool Kaldi-NL performs at annotating target words in IDS vs. ADS. We found that Kaldi-NL only found 55.8% of target words in IDS, while it annotated 66.8% correctly in ADS. In Experiment 2, we aimed to assess the difficulties in annotating IDS more broadly by transcribing all IDS utterances manually and comparing the word error rates (WERs) of two different ASR systems: Kaldi-NL and WhisperX. We found that WhisperX performs significantly better than Kaldi-NL. While there is much room for improvement, the results show that automatic transcriptions provide a promising starting point for researchers who have to transcribe a large amount of speech directed at infants

Prosodic and other cues to speech recognition failures

In spoken dialogue systems, it is important for the system to know how likely a speech recognition hypothesis is to be correct, so it can reject misrecognized user turns, or, in cases where many errors have occurred, change its interaction strategy or switch the caller to a human attendant. We have identified prosodic features which predict more accurately when a recognition hypothesis contains errors than the acoustic confidence scores traditionally used in automatic speech recognition in spoken dialogue systems. We describe statistical comparisons of features of correctly and incorrectly recognized turns in the TOOT train information corpus and the W99 conference registration corpus, which reveal significant prosodic differences between the two sets of turns. We then present machine learning results showing that the use of prosodic features, alone and in combination with other automatically available features, can predict more accurately whether or not a user turn was correctly recognized, when compared to the use of acoustic confidence scores alone. Ó 2004 Published by Elsevier B.V