Today, signal processing research has a significantly widened its scope compared with just a few years ago [4], and machine learning has been an important technical area of the signal processing society. Since 2006, deep learning—a new area of machine learning research—has emerged [7], impacting a wide range of signal and information processing work within the traditional and the new, widened scopes. Various workshops, such as the 2009 ICML Workshop on Learning Feature Hierarchies; the 2008 NIPS Deep Learning Workshop: Foundations and Future Directions; and the 2009 NIPS Workshop on Deep Learning for Speech Recognition and Related Applications as well as an upcoming special issue on deep learning for speech and language processing in IEEE Transactions on Audio, Speech, and Language Processing (2010) have been devoted exclusively to deep learning and its applications to classical signal processing areas. We have also seen the government sponsor research on deep learning.