PGD-N2L: A Parameter-Guided Disentanglement Approach for Normal-To-Lombard Speech Conversion

The Normal-To-Lombard (N2L) speech conversion can effectively improve speech intelligibility in noisy communication scenarios and serve as a data augmentation tool for various speech-related algorithms. However, existing N2L methods did not aim to disentangle the Lombard effect from other speech attributes, leading to incomplete conversions. In this paper, we propose a Parameter-Guided Disentanglement approach for N2L speech conversion (PGD-N2L) which decomposes speech into linguistic content, speaker identity, and Lombard effect. To extract disentangled linguistic content, we propose a DeLomb-Based content encoder. To extract disentangled speaker identity and Lombard effect, we propose a style encoder that combines a fine-tuned speaker encoder and a learnable Lombard encoder to form a personalized style embedding. Furthermore, an En-Lomb-Based injection module is designed to accurately integrate the target Lombard effect and speaker identity into the linguistic content based on personalized style embedding, ensuring complete Lombard conversion. Experimental results demonstrate that our proposed method outperforms existing N2L models in speech intelligibility, acoustic similarity, and speech quality. Ablation studies confirm that the fine-tuned speaker encoder and the De-Lomb block effectively improve speech intelligibility and acoustic similarity, while the En-Lomb block enables the converted speech to more closely match the target Lombard speech.