 Preprocessing  The speech data is pre-processed by extracting Kaldi-compliant 80-channel log mel-filter bank features automatically from WAV/FLAC audio files via PyKaldi or torchaudio. Further utterance-level CMVN (cepstral mean and variance normalization) is applied to each example.  The texts are lowercased and tokenized using SentencePiece and a vocabulary size of 10,000.   