A speech recognition apparatus, the apparatus comprising: a preprocessor configured to extract select frames from all frames of a first speech of a user; and a score calculator configured to calculate an acoustic score of a second speech, made up of the extracted select frames, by using a Deep Neural Network, DNN,-based acoustic model, and to calculate an acoustic score of frames, of the first speech, other than the select frames based on the calculated acoustic score of the second speech, wherein the score calculator: is adapted to use acoustic scores of frames of the second speech, calculated by the acoustic model, as determined acoustic scores of respective frames of the first speech that correspond to the frames of the second speech and is further adapted to use, as an acoustic score of an adjacent frame, which is one of the frames of the first speech other than the select frames and adjacent to one or more of the respective frames of the first speech, a statistical value obtained by applying a weighted value to each determined acoustic score of two of the select frames of the first speech, or to each determined acoustic score of two frames of the second speech corresponding to the two of the select frames of the first speech, based on respectively determined temporal distances between the adjacent frame and the two frames of the first speech. a preprocessor configured to extract select frames from all frames of a first speech of a user; and a score calculator configured to calculate an acoustic score of a second speech, made up of the extracted select frames, by using a Deep Neural Network, DNN,-based acoustic model, and to calculate an acoustic score of frames, of the first speech, other than the select frames based on the calculated acoustic score of the second speech, wherein the score calculator: is adapted to use acoustic scores of frames of the second speech, calculated by the acoustic model, as determined acoustic scores of respective frames of the first speech that correspond to the frames of the second speech and is further adapted to use, as an acoustic score of an adjacent frame, which is one of the frames of the first speech other than the select frames and adjacent to one or more of the respective frames of the first speech, a statistical value obtained by applying a weighted value to each determined acoustic score of two of the select frames of the first speech, or to each determined acoustic score of two frames of the second speech corresponding to the two of the select frames of the first speech, based on respectively determined temporal distances between the adjacent frame and the two frames of the first speech. is adapted to use acoustic scores of frames of the second speech, calculated by the acoustic model, as determined acoustic scores of respective frames of the first speech that correspond to the frames of the second speech and is further adapted to use, as an acoustic score of an adjacent frame, which is one of the frames of the first speech other than the select frames and adjacent to one or more of the respective frames of the first speech, a statistical value obtained by applying a weighted value to each determined acoustic score of two of the select frames of the first speech, or to each determined acoustic score of two frames of the second speech corresponding to the two of the select frames of the first speech, based on respectively determined temporal distances between the adjacent frame and the two frames of the first speech.