1. A data converting apparatus, comprising: a decomposing unit subjecting temporal alteration data of a stimulus value to wavelet decomposition to extract a plurality of time-frequency components contained in the temporal alteration data; a weighting unit weighting the plurality of the extracted time-frequency components with weighting coefficients which are predetermined based on a relationship between a temporal alteration of a stimulus value and a temporal alteration of a sensitivity of human beings to the stimulus value; and a synthesizing unit subjecting the plurality of the weighted time-frequency components to wavelet synthesis to estimate a sensitivity brought to human beings when the stimulus value is subjected to temporal alteration according to the temporal alteration data.