Method and apparatus with speech recognition

A speech recognition apparatus comprising:

• one or more processors configured to:
• extract a speech feature from an input speech to be recognized;
• estimate a first sequence of first subwords corresponding to at least one portion of the input speech based on the extracted speech feature;
• convert the first sequence to a second sequence of at least one second subword by combining at least two of the first subwords;
• and
• recognize the input speech by performing a recognition of a remaining portion of the input speech based on the second sequence.

A processor-implemented speech recognition method comprising:

• generating, at an output layer of a recurrent neural network (RNN), a first subword based on a feature extracted from a speech signal;
• generating, at the output layer of the RNN, a second subword based on the first subword;
• generating a third subword by combining the first and the second subwords;
• generating, at the output layer of the RNN, a fourth subword based on the third subword;
• and
• recognizing the speech signal based a determined sequence of the third and fourth subwords.