18. The method of claim 15 , wherein the calculating of the acoustic score of the first speech comprises using two acoustic scores of frames of the second speech as acoustic scores of two frames of the first speech that correspond to the two frames of the second speech and using at least one acoustic score of the frames of the second speech for an acoustic score of an adjacent frame, of the first speech, that is adjacent to the two frames of the first speech.
15. A processor-implemented speech recognition method, the method comprising: receiving input of first speech to be recognized; extracting some frames from all frames of the first speech; generating a second speech by using the extracted frames; calculating an acoustic score of the second speech by using a Deep Neural Network (DNN)-based acoustic model; calculating an acoustic score for one or more frames, other than the extracted frames, of the first speech based on the calculated acoustic score of the second speech; and recognizing the first speech based on the calculated acoustic score of the second speech and the calculated acoustic score for the one or more frames of the first speech.