When durian fruit become ripe, both pulp and husk (peel) losewater and shrink. As the pulp shrinks more, this results in a spacebetween pulp and husk. The onset of the presence of this spaceis well correlated with the onset of good eating quality. When thefruit surface is knocked with an object such as a knife, the grower orother specialist will be able to tell by the acoustic response if thereis a cavity, thus if the fruit is ripe. In the present tests, the initialparameter for ripeness was the acoustic response. This response,if indicating that a cavity was present, was subsequently tested bythe quality panel.