SpeechPrompt: An Exploration of Prompt Tuning on Generative Spoken Language Model for Speech Processing Tasks (2203.16773v3)

Abstract: Speech representations learned from Self-supervised learning (SSL) models can benefit various speech processing tasks. However, utilizing SSL representations usually requires fine-tuning the pre-trained models or designing task-specific downstream models and loss functions, causing much memory usage and human labor. Recently, prompting in NLP has been found to be an efficient technique to leverage pre-trained LLMs (LMs). Specifically, prompt tuning optimizes a limited number of task-specific parameters with a fixed pre-trained model; as a result, only a small set of parameters is needed to be stored for each task. Prompt tuning improves computation and memory efficiency by leveraging the pre-trained LM's prediction ability. Nevertheless, such a paradigm is little studied in the speech community. We report in this paper the first exploration of the prompt tuning paradigm for speech processing tasks based on Generative Spoken LLM (GSLM). Experiment results show that the prompt tuning technique achieves competitive performance in speech classification tasks with fewer trainable parameters than fine-tuning specialized downstream models. We further study the technique in challenging sequence generation tasks. Prompt tuning also demonstrates its potential, while the limitation and possible research directions are discussed in this paper. The source code is available on https://github.com/ga642381/SpeechPrompt.

An Analysis of "SpeechPrompt: An Exploration of Prompt Tuning on Generative Spoken LLM for Speech Processing Tasks"

The research paper titled "SpeechPrompt: An Exploration of Prompt Tuning on Generative Spoken LLM for Speech Processing Tasks" presents a thorough investigation into the application of prompt tuning techniques in the domain of speech processing, particularly leveraging the Generative Spoken LLM (GSLM). The authors explore an innovative approach to enhance the efficiency of speech processing models by adopting methodologies traditionally utilized in NLP, specifically prompt tuning.

The primary motivation driving this work stems from the limitations associated with traditional approaches in leveraging Self-supervised Learning (SSL) models for speech tasks. These approaches typically require extensive fine-tuning of pre-trained models or the development of specialized downstream models, leading to substantial memory usage and human labor. In contrast, prompt tuning offers a more resource-efficient paradigm, focusing only on optimizing a minimal number of task-specific parameters without altering the foundational pre-trained model.

By employing GSLM as the backbone, the paper is pioneering in that it applies prompting frameworks, which have predominantly been examined within NLP, to various speech processing contexts such as Keyword Spotting (KS), Intent Classification (IC), Automatic Speech Recognition (ASR), and Slot Filling (SF). The experimental results indicate that prompt tuning can achieve competitive performance on classification tasks with significantly fewer trainable parameters compared to approaches that necessitate full model adaptations.

In quantitative terms, the framework showcased performances comparable to those of specialized downstream models in tasks like KS and IC, achieving accuracies of 95.16% and 98.40%, respectively, using the HuBERT model. This is particularly notable given the reduced computational footprint — for instance, only 0.08M parameters were trainable for KS, compared to full model optimization. Furthermore, prompt tuning revealed potential in handling multi-label classification evidenced in the IC task, outperforming both fully fine-tuned LLMs and downstream models: a promising indication of its applicability in learning correlations between labels.

Nonetheless, the paper identifies challenges when extending prompt tuning to sequence generation tasks such as ASR and SF. Performance was less competitive, as reflected in a 34.17% Word Error Rate (WER) for ASR using HuBERT, underscoring inherent limitations with existing generative models when handling long sequences. It is posited that these challenges may be due to the model's causal nature, which affects its capability to manage the complex dynamics of extensive output sequences, an issue similarly noted in text generation within NLP.

The paper also endeavors to explore the extent of effectiveness brought by varying prompt lengths, revealing a tendency for performance improvement with increased prompt lengths, at least in the context of KS and IC. Between input prompt tuning and deep prompt tuning, the latter was observed to yield better results, although input prompt tuning still maintained competitive performance when optimized with a sufficient number of parameters.

The paper concludes with discussions on the criticality of effective verbalizer design to improve performance since mappings between learned units and task-specific labels were limited by heuristic methods. Moreover, the paper hints at the requirement for more powerful, diverse speech LLMs akin to those available in NLP to broaden the adoption of prompt techniques across more varied and complex tasks in the speech processing field.

The contribution of this paper lies in its novel application of the prompting paradigm within speech processing, showcasing its potential to streamline and enhance computational efficiency in model adaptation for various tasks. It lays the groundwork for further exploration and development of unified, parameter-efficient frameworks applicable across multimodal AI tasks. Researchers motivated by this approach are encouraged to explore larger, more complex generative LLMs that may overcome current challenges and expand the versatility of prompt-based learning within the speech community.