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Enhancing Noise Robustness in Speech Emotion Recognition through Two-level Refinement Network and Speech Enhancement


Core Concepts
A Two-level Refinement Network (TRNet) that leverages a pre-trained speech enhancement module to improve the robustness of speech emotion recognition in noisy environments, without compromising performance in clean environments.
Abstract
The paper introduces TRNet, a novel approach to address the challenge of environmental noise in speech emotion recognition (SER). The key components of TRNet are: Speech Enhancement (SE) Module: A pre-trained SE module, specifically the Conformer-based Metric Generative Adversarial Network (CMGAN), is employed for front-end noise reduction and noise level estimation. SNR-aware Module: This module dynamically adjusts the importance of the SE module based on the estimated signal-to-noise ratio (SNR). It performs low-level feature compensation by approximating the target speech spectrogram from the noisy and enhanced spectrograms. SER Module: Two identical SER modules are used - one pre-trained on clean data and the other fine-tuned on both clean and noisy data. The high-level representation calibration is performed to align the deep representations extracted from the target and approximated spectrograms. Experimental results on the IEMOCAP dataset demonstrate that TRNet can effectively couple the SE and SER modules, improving the system's robustness in both matched and unmatched noisy environments, while maintaining performance in clean environments. The ablation study and visualization analysis further validate the roles of SNR estimation and the characteristics of deep representations in TRNet.
Stats
The observed signal x is a mixture of the target speech signal xs and noise signal xn, i.e., x = xs + xn. The speech samples were contaminated at 5 different SNRs (20 dB, 15 dB, 10 dB, 5 dB, and 0 dB) by random noise samples from the ESC-50 and MUSAN datasets.
Quotes
"One persistent challenge in Speech Emotion Recognition (SER) is the ubiquitous environmental noise, which frequently results in diminished SER performance in practical use." "To increase the robustness of SER in noisy environments, one strategy involves focusing on feature engineering, exploring the design of feature sets that are insensitive to noise contamination." "Recent research has explored methods that integrate speech enhancement (SE) with SER models, aiming to improve the robustness of back-end SER models under noisy environments through noise reduction pre-processing."

Deeper Inquiries

How can the proposed TRNet framework be extended to handle more complex acoustic environments, such as reverberant or multi-speaker scenarios?

To extend the TRNet framework for handling more complex acoustic environments, such as reverberant or multi-speaker scenarios, several modifications and additions can be considered: Reverberant Environments: Incorporating reverberation-robust features or modules into TRNet can help mitigate the effects of reverberation. Techniques like dereverberation algorithms or reverberation-robust feature extraction methods can be integrated into the SE module to preprocess the input signals effectively. Multi-Speaker Scenarios: For scenarios with multiple speakers, the model can be enhanced to incorporate speaker diarization techniques to separate and identify individual speakers. This can involve speaker embedding networks or speaker clustering methods to handle overlapping speech segments. Multi-Channel Audio: Utilizing multi-channel audio data can provide spatial information that aids in separating speech sources in complex acoustic environments. TRNet can be extended to process multi-channel inputs and leverage spatial features for improved noise robustness. Adversarial Training: Introducing adversarial training techniques can enhance the model's ability to generalize to unseen or challenging acoustic conditions. Adversarial examples can be generated to simulate diverse acoustic scenarios, forcing the model to learn more robust representations. Dynamic Adaptation: Implementing adaptive mechanisms that dynamically adjust model parameters based on the acoustic environment can improve performance. Techniques like domain adaptation or transfer learning can be employed to fine-tune the model for specific environmental conditions. By incorporating these enhancements, TRNet can be tailored to handle a broader range of complex acoustic environments, ensuring robust performance in diverse real-world scenarios.

How can the insights gained from the SNR estimation and deep representation analysis in TRNet be applied to other speech-related tasks beyond emotion recognition?

The insights obtained from the SNR estimation and deep representation analysis in TRNet can be leveraged in various other speech-related tasks to enhance performance and robustness: Speaker Recognition: SNR estimation can aid in noise-robust speaker recognition by adapting the model to varying noise levels. Deep representation analysis can improve speaker embedding quality, leading to more discriminative speaker representations. Speech Enhancement: The SNR-aware module insights can be applied to speech enhancement tasks to dynamically adjust noise reduction strategies based on estimated SNRs. Deep representation analysis can guide the enhancement process to preserve essential speech features. Automatic Speech Recognition (ASR): SNR estimation can optimize noise reduction for ASR systems, improving transcription accuracy in noisy environments. Deep representation analysis can help extract informative features for better speech recognition performance. Language Identification: Utilizing SNR estimation can enhance language identification systems in noisy conditions by adapting language models based on noise levels. Deep representation analysis can aid in extracting language-specific features for accurate identification. By applying the knowledge gained from SNR estimation and deep representation analysis in TRNet to these speech-related tasks, overall system performance can be enhanced, leading to more robust and accurate outcomes across various applications.
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