Computer support for learners of spoken English

Abstract: This thesis concerns the use of speech technology to support the process of learning the English language. It applies theories of computer-assisted language learning and second language acquisition to address the needs of beginning, intermediate and advanced students of English for specific purposes.The thesis includes an evaluation of speech-recognition-based pronunciation software, based on a controlled study of a group of immigrant engineers. The study finds that while the weaker students may have benefited from their software practice, the pronun¬ciation ability of the better students did not improve.The linguistic needs of advanced and intermediate Swedish-native students of English are addressed in a study using multimodal speech synthesis in an interactive exercise demonstrating differences in the placement of lexical stress in two Swedish-English cognates. A speech database consisting of 28 ten-minute oral presentations made by these learners is described, and an analysis of pronunciation errors is pre¬sented. Eighteen of the presentations are further analyzed with regard to the normalized standard deviation of fundamental frequency over 10-second long samples of speech, termed pitch variation quotient (PVQ). The PVQ is found to range from 6% to 34% in samples of speech, with mean levels of PVQ per presentation ranging from 11% to 24%. Males are found to use more pitch variation than females. Females who are more proficient in English use more pitch variation than the less profi¬cient females. A perceptual experiment tests the relationship between PVQ and impressions of speaker liveliness. An overall correlation of .83 is found. Temporal variables in the presentation speech are also studied.A bilingual database where five speakers make the same presentation in both English and Swedish is studied to examine effects of using a second language on presentation prosody. Little intra-speaker difference in pitch variation is found, but these speakers speak on average 20% faster when using their native language. The thesis concludes with a discussion of how the results could be applied in a proposed feedback mechanism for practicing and assessing oral presentations, concept¬ualized as a ‘speech checker.’ Potential users of the system would include native as well as non-native speakers of English.