End-to-end keyword search system based on attention mechanism and energy scorer for low resource languages

Keyword search (KWS) means searching for keywords given by the user from continuous speech. Conventional KWS systems are based on Automatic Speech Recognition (ASR), where the input speech has to be first processed by the ASR system before keyword searching. In the recent decade, as deep learning and deep neural networks (DNN) become increasingly popular, KWS systems can also be trained in an end-to-end (E2E) manner. The main advantage of E2E KWS is that there is no need for speech recognition, which makes the training and searching procedure much more straightforward than the traditional ones. This article proposes an E2E KWS model, which consists of four parts: speech encoder-decoder, query encoder-decoder, attention mechanism, and energy scorer. Firstly, the proposed model outperforms the baseline model. Secondly, we find that under various supervision, character or phoneme sequences, speech or query encoders can extract the corresponding information, resulting in different performances. Moreover, we introduce an attention mechanism and invent a novel energy scorer, where the former can help locate keywords. The latter can make final decisions by considering speech embeddings, query embeddings, and attention weights in parallel. We evaluate our model on low resource conditions with about 10-hour training data for four different languages. The experiment results prove that the proposed model can work well on low resource conditions.