*6.2.4 Speech processing*

Note that speech signals exhibit spectral variations and correlations, CNNs are very suitable to reduce them. Therefore, CNNs can also be utilized for the task of speech processing, such as speech recognition. Sainath1 et al. [53] applied deep CNNs for large vocabulary speech tasks. In [54–56], the CNNs are used for speech recognition. And the fundamental methods are very similar, both of them use the CNNs to extract features from the raw input, and then these features are fed into an decoder for the specific learning tasks.
