A speech emotion recognition (SER) system deployed on a real-world application can encounter speech contaminated with unconstrained background noise. To deal with this issue,
a speech enhancement (SE) module can be attached to the SER system to compensate for the environmental difference of an input. Although the SE module can improve the quality and intelligibility of a given speech, there is a risk of affecting discriminative acoustic features for SER that are resilient to environmental differences. Exploring this idea, we propose to enhance only weak features that degrade the emotion recognition performance. Our model first identifies weak feature sets by using multiple models trained with one acoustic feature at a time using clean speech. After training the single-feature models, we rank each speech feature by measuring three criteria: performance, robustness, and a joint rank ranking that combines performance and robustness. We group the weak features by cumulatively incrementing the features from the bottom to the top of each rank. Once the weak feature set is defined, we
only enhance those weak features, keeping the resilient features unchanged. We implement these ideas with the low-level descriptors (LLDs). We show that directly enhancing the weak LLDs leads to better performance than extracting LLDs from an enhanced speech signal. Our experiment with clean and noisy versions of the MSP-Podcast corpus shows that the proposed approach yields a 17.7% (arousal), 21.2% (dominance), and 3.3% (valence) performance gains over a system that enhances all the LLDs for the 10dB signal-to-noise ratio (SNR) condition.