1. A method comprising: receiving, in a processor, an acoustic input signal; and processing the acoustic input signal with a plurality of acoustic recognition processes to recognize a predetermined target sound within the acoustic input signal, the acoustic input signal being temporally divided into a plurality of frames, the plurality of acoustic recognition processes being implemented using a single Viterbi search of a plurality of states corresponding to acoustic units of an acoustic model of the predetermined target sound, the plurality of states including initial states and final states of the acoustic model, wherein the initial states are reset on each frame if a score for the initial state on a previous frame is below a first threshold, said score is calculated for a plurality of said states on each frame, the calculating comprising increasing the score by a per frame offset so that scores of different durations are comparable, and a result is generated when a score of a final state increases above a second threshold.