Recently, Boonmung et al. (2006) attempted to classify pineapple quality (unripe, ripe, overripe) using resonant frequency and level of soluble solids in the fruit as guides. The acoustic property tester developed by Jarimopas et al. (2004) was used to measure the frequency spectrumof the pineapple subjected to a single hit. An artificial neural network for classification was most efficient with the maximum amplitude of the resonant frequency and the soluble solids included in the model.