1. A method of keyword recognition in a speech signal, the method comprising: sampling, by one or more processors, the speech signal in one or more frames; determining, by the one or more processors, a first likelihood score of one or more features of a frame, of the one or more frames, of the speech signal being associated with one or more states in a first model, wherein the one or more states in the first model correspond to one or more tied triphone states of a keyword to be recognized in the speech signal, and wherein the one or more features comprise a frequency of an audio in the frame; determining, by the one or more processors, a second likelihood score of the one or more features of the frame of the speech signal being associated with one or more states in a second model, wherein the one or more states in the second model correspond to one or more monophone states of the keyword to be recognized in the speech signal; determining, by the one or more processors, a third likelihood score based on the first likelihood score and the second likelihood score, wherein the third likelihood score is deterministic of a likelihood of the frame corresponding to keywords other than the keyword; and determining, by the one or more processors, a presence of the keyword in the speech signal based on the first likelihood score and the third likelihood score.