1. A speech recognition apparatus based on a deep-neural-network (DNN) sound model, comprising: a memory; and a processor configured to execute a program stored in the memory, wherein, as the program is executed, the processor generates sound-model state sets corresponding to a plurality of pieces of set training speech data included in multi-set training speech data, generates a multi-set state cluster from the sound-model state sets, and sets the multi-set training speech data as an input node and the multi-set state cluster as an output node so as to learn a DNN structured parameter, and when a user's speech and characteristic information thereof are received via a user interface, the processor recognizes the user's speech on the basis of the learned DNN structured parameter by setting a sound-model state set corresponding to the characteristic information of the user's speech as an output node.