Voiced/unvoiced/silence classification of speech using 2-stage neural networks with delayed decision input

This paper proposes a two stage feed-forward neural network classifier capable of determining voiced, unvoiced and silence in the first stage and refining unvoiced and silence decisions in the second stage. Delayed decision from the previous frame's classification along with preliminary decision by the first stage network, zero-crossing ratio and energy ratio enables the second stage to correct the mistakes made by the first stage in classifying unvoiced and silence frames. Comparisons with a single stage classifier demonstrates the necessity of two stage classification techniques. It also shows that the proposed classifier performs excellently.