Ensemble feature selection for domain adaptation in speech emotion recognition

When emotion recognition systems are used in new domains, the classification performance usually drops due to mismatches between training and testing conditions. Annotations of new data in the new domain is expensive and time demanding. Therefore, it is important to design strategies that efficiently use limited amount of new data to improve the robustness of the classification system. The use of ensembles is an attractive solution, since they can be built to perform well across different mismatches. The key challenge is to create ensembles that are diverse. This paper proposes the use of active learning along with feature selection to build a diverse ensemble that performs well in the new domain. The diversity and accuracy of the ensemble are achieved by (1) training emotional classifiers with bias toward specific emotions, (2) eliminating overlap in the feature sets of the ensemble, and (3) conducting feature selection by maximizing the performance over the new labeled data. We study various data selection criteria, and different sample sizes to determine the best approach toward building a stable diverse ensemble that generalize well on new domains.