Abstract. In this paper, the spherical mode shapes corresponding to the resonant peaks in the frequency response spectrum were obtained. The apple defect was made by either injecting the reagent HC1 into the apple or by making holes in the apple. It was found that the apple defect may split one S₂₀ peak into two or even more S₂₀ peaks in the frequency spectrum. The effect relies on the location and size of the defect in the apple as well as the measurement position of the impact and the re­sponse sensors. In the presence of the defect, this technique becomes unreliable in firmness evaluation, however it could possibly be used for the indication of the existence of the defect inside the apple.