  Attention is the core mechanism of today's most used architectures for
natural language processing and has been analyzed from many perspectives,
including its effectiveness for machine translation-related tasks. Among these
studies, attention resulted to be a useful source of information to get
insights about word alignment also when the input text is substituted with
audio segments, as in the case of the speech translation (ST) task. In this
paper, we propose AlignAtt, a novel policy for simultaneous ST (SimulST) that
exploits the attention information to generate source-target alignments that
guide the model during inference. Through experiments on the 8 language pairs
of MuST-C v1.0, we show that AlignAtt outperforms previous state-of-the-art
SimulST policies applied to offline-trained models with gains in terms of BLEU
of 2 points and latency reductions ranging from 0.5s to 0.8s across the 8
languages.
