Described are techniques to recognize spoken wake word (WW) or command for human-machine interface using a speech recognition system that does not require any WW/command-matching speech data for training. The system uses the text or grapheme representation of the WW or commands for training before deployment. The technique includes receiving a target phrase for recognition by a speech recognition model. The technique includes analyzing a sequence of acoustic units representative of the target phrase when the target phrase is spoken to generate offline analysis data. The technique further includes constructing the speech recognition model based on the offline analysis data to decode speech signals of the target phrase according to the acoustic units. The technique further includes processing speech based on the speech recognition model to detect a presence of the target phrase.