Improving Spoken Question Answering Using Contextualized Word Representation

While question answering (QA) systems have witnessed great breakthroughs in reading comprehension (RC) tasks, spoken question answering (SQA) is still a much less investigated area. Previous work shows that existing SQA systems are limited by catastrophic impact of automatic speech recognition (ASR) errors \cite{li2018spoken} and the lack of large-scale real SQA datasets \cite{lee2018odsqa}. In this paper, we propose using contextualized word representations to mitigate the effects of ASR errors and pretraining on existing textual QA datasets to mitigate the data scarcity issue. New state-of-the-art results have been achieved using contextualized word representations on both the artificially synthesised and real SQA benchmark data sets, with 21.5 EM/18.96 F1 score improvement over the sub-word unit based baseline on the Spoken-SQuAD \cite{li2018spoken} data, and 13.11 EM/10.99 F1 score improvement on the ODSQA data \cite{lee2018odsqa}. By further fine-tuning pre-trained models with existing large scaled textual QA data, we obtained 38.12 EM/34.1 F1 improvement over the baseline of fine-tuned only on small sized real SQA data.