Handling emotional speech: a prosody based data augmentation technique for improving neutral speech trained ASR systems

In this paper, the effect of emotional speech on the performance of neutral speech trained ASR systems is studied. Prosody-modification based data augmentation is explored to compensate the affected ASR performance due to emotional speech. The primary motive is to develop an Telugu ASR system that is least affected by these emotion based intrinsic speaker related acoustic variations. Two factors contributing towards the intrinsic speaker related variability that are focused in this research are the fundamental frequency [\((F_0)\) or pitch] and the speaking rate variations. To simulate ASR task, we performed the training of our ASR system on neutral speech and tested it for data from emotional as well as neutral speech. Compared to the performance metrics of neutral speech at testing stage, emotional speech performance metrics are extremely degraded. This performance degradation is observed due to the difference in the prosody and speaking rate parameters of neutral and emotional speech. To overcome this performance degradation problem, prosody and speaking rate parameters are varied and modified to create the newer augmented versions of the training data. The original and augmented versions of the training data are pooled together and re-trained in order to capture greater emotion-specific variations. For the Telugu ASR experiments, we used Microsoft speech corpus for Indian languages(MSC-IL) for training neutral speech and Indian Institute of Technology Kharagpur Simulated Emotion Speech Corpus (IITKGP-SESC) for evaluating emotional speech. The basic emotions of anger, happiness and sad are considered for evaluation along with neutral speech.