One of the major difficulties with developing advanced control strategies for cooking extruders is the lack of cheap, easy to implement, on-line "product quality" estimators. One of the most promising developments in this area is the recent emergence of acoustics based estimation techniques. The basis of this approach relies on the fact that as the extrudate leaves the die, the water content partially flashes causing the extrudate to expand. There are discernible differences in sound as this steam escapes when different products are being extruded. It is the interaction between this expansion, the rheology of the extrudate, and the resultant bubble size distribution that gives the final product many of the qualities that both the manufacturer and the consumer are looking for.-This paper outlines the techniques used to analyse experimental acoustic data and develop correlations to predict final extruder product properties.