Semantic Mask for Transformer based End-to-End Speech Recognition
Table 2: Ablation test of different masking methods. The fourth line is a default setting of SpecAugment. The fifth line uses word mask to replace random time mask, and the last line combines both methods on the time axis.
['Time wrap', 'Time mask', 'Freq mask', 'Word mask', 'Dev clean', 'Dev other', 'Test clean', 'Test other']
According to the comparison between the second line and the third line, we find that the word masking is slightly better than the time masking if other SpecAugment operations are absent. When it combined with other SpecAugment methods, the word masking is still better than the time masking, indicating the superior of the semantic masking. We also attempt to mask phrases and add white-noise to masked regions, but there is no improvement according to several experiment comparisons.