Enhancing Monotonic Multihead Attention for Streaming ASR
Table 2: Results of offline MMA models on the dev sets with head-synchronous beam search decoding. HeadDrop is used in all models. Hma=4.
['ID', '[ITALIC] Dlm', '[ITALIC] w', '[ITALIC] Hca', 'dev-clean / dev-other %WER', 'dev-clean / dev-other  [ITALIC] Rcov', 'dev-clean / dev-other  [ITALIC] Rstr']
Head-synchronous beam search decoding improves streamability: Next, the results with head-synchronous beam search decoding are shown in Head-synchronous decoding effectively improved both boundary coverage and streamability. We found that if a head cannot detect the boundary around the corresponding actual acoustic boundary, it tends to stop around the next acoustic boundary twice to compensate the failure when using a standard beam search. Head-synchronous decoding alleviated this mismatch of boundary positions and led to small WER improvement except for B3 on the dev-clean set.