Recent advancements in end-to-end (E2E) modeling have notably improved automatic speech recognition (ASR) systems; however, far-field speech recognition (FSR) remains challenging due to signal degradation from factors such as low signal-to-noise ratio, reverberation, and interfering sounds. This requires richer training data and multi-channel speech enhancement. To address this gap, we introduce Mixer, a novel data augmentation technique designed to further enhance the performance of large-scale pre-trained models for FSR. Mixer interpolates and mixes feature representations of speech samples and their corresponding losses, extending the MixSpeech framework to intermediate layers of Whisper. Additionally, we propose Mixer-C, which further leverages multi-channel information by combining speech from different microphone channels using a channel selector. Experimental results demonstrate that Mixer significantly outperforms existing methods, including SpecAugment, achieving a relative word error rate (WER) reduction of 3.6% compared to the baseline. Furthermore, Mixer-C offers an additional WER improvement of 2.2%, showcasing its efficacy in improving FSR accuracy.

Addressing the issue that the Transformer decoder struggles to capture local features for monotonic alignment in speech recognition, and simultaneously incorporating language model cold fusion training into the decoder, an enhanced decoder-based speech recognition model is investigated. The enhanced decoder separates and combines the two attention mechanisms in the Transformer decoder into cross-attention layers and a self-attention language model module. The cross-attention layers are utilized to capture local features more efficiently from the encoder output, and the self-attention language model module is used to pre-train with additional domain-related text, followed by cold fusion training. Experimental results on the Mandarin Aishell-1 dataset demonstrate that when the encoder is a Conformer, the enhanced decoder achieves a 16.1% reduction in character error rate compared to the Transformer decoder. Furthermore, when the language model is pre-trained with suitable text data, the performance of the cold fusion-trained model is further enhanced.