1. A system comprising: a computer-readable memory storing executable instructions; and one or more physical computer processors in communication with the computer-readable memory, wherein the one or more physical computer processors are programmed by the executable instructions to at least: obtain audio data regarding a user utterance, the audio data comprising a sequence of frames; identify, for a current frame of the sequence of frames, (1) one or more speech recognition decoding graph states corresponding to the current frame, and (2) a window of frames preceding the current frame in the sequence of frames; generate, for a first state of the one or more speech recognition decoding graph states, a parameter of a probability density function, wherein the parameter is generated using an artificial neural network, and wherein input into the artificial neural network comprises data regarding the first state and a plurality of feature vectors corresponding to the window of frames; generate, for the first state of the one or more speech recognition decoding graph states, a first score using a feature vector corresponding to the current frame and the parameter of the probability density function generated using the first state; and select at least one state to add to the speech recognition decoding graph based at least partly on the first score and the first state.