The effects of English proficiency on the processing of Bulgarian-accented English by Bulgarian-English bilinguals

This dissertation explores the potential benefit of listening to and with one’s first-language accent, as suggested by the Interspeech Intelligibility Benefit Hypothesis (ISIB). Previous studies have not consistently supported this hypothesis. According to major second language learning theories, the listener’s second language proficiency determines the extent to which the listener relies on their first language phonetics. Hence, this thesis provides a novel approach by focusing on the role of English proficiency in the understanding of Bulgarian-accented English for Bulgarian-English bilinguals. The first experiment investigated whether evoking the listeners’ L1 Bulgarian phonetics would improve the speed of processing Bulgarian-accented English words, compared to Standard British English words, and vice versa. Listeners with lower English proficiency processed Bulgarian-accented English faster than SBE, while high proficiency listeners tended to have an advantage with SBE over Bulgarian accent. The second experiment measured the accuracy and reaction times (RT) in a lexical decision task with single-word stimuli produced by two L1 English speakers and two Bulgarian-English bilinguals. Listeners with high proficiency in English responded slower and less accurately to Bulgarian-accented speech compared to L1 English speech and compared to lower proficiency listeners. These accent preferences were also supported by the listener’s RT adaptation across the first experimental block. A follow-up investigation compared the results of L1 UK English listeners to the bilingual listeners with the highest proficiency in English. The L1 English listeners and the bilinguals processed both accents with similar speed, accuracy and adaptation patterns, showing no advantage or disadvantage for the bilinguals. These studies support existing models of second language phonetics. Higher proficiency in L2 is associated with lesser reliance on L1 phonetics during speech processing. In addition, the listeners with the highest English proficiency had no advantage when understanding Bulgarian-accented English compared to L1 English listeners, contrary to ISIB. Keywords: Bulgarian-English bilinguals, bilingual speech processing, L2 phonetic development, lexical decision, proficienc

Automatic Speech Recognition for Low-resource Languages and Accents Using Multilingual and Crosslingual Information

This thesis explores methods to rapidly bootstrap automatic speech recognition systems for languages, which lack resources for speech and language processing. We focus on finding approaches which allow using data from multiple languages to improve the performance for those languages on different levels, such as feature extraction, acoustic modeling and language modeling. Under application aspects, this thesis also includes research work on non-native and Code-Switching speech