15. One or more computer-readable storage memory devices for storing computer-readable instructions, the computer-readable instructions when executed by one or more processing devices, the computer-readable instructions comprising code configured to: train a first neural network to recognize a higher level of a speech characteristic in a first speech signal from a mixed speech sample comprising a single audio channel; train a second neural network to recognize a lower level of the speech characteristic in a second speech signal from the mixed speech sample; train a third neural network to estimate a switching probability for each frame; and decode the mixed speech sample with the first neural network, the second neural network, and the third neural network by optimizing the joint likelihood of observing the two speech signals, the joint likelihood meaning a probability that a specific frame is a switching point of the speech characteristic.
20. The computer-readable storage memory devices of claim 15 , comprising code configured to: train a third neural network to predict energy switching; predict whether energy is switching from one frame to a next frame; and decode the mixed speech sample based on the prediction.