1. A computation apparatus comprising: range table creation means configured to create a range table that maps each one of a first plurality of ranges of input values for one or more audio signals to a corresponding discrete value, the corresponding discrete value being a computation result obtained by applying a nonlinear computation on at least one input value in the one of the first plurality of ranges of input values for the one or more audio signals; and search means configured to search, when an input value for an input audio signal is input, in the range table for a range in which the input value is included and output a discrete value corresponding to the searched range, wherein the first plurality of ranges comprises a selected second plurality of ranges, wherein each range of the second plurality of ranges corresponds to at least one first discrete value the output occurrence rate of which is higher than a selected occurrence rate, and wherein the search means is configured to: determine, without using a hash table, whether the input value is included in any one of the selected second plurality of ranges; if it is determined that the input value is in one of the selected second plurality of ranges, output a discrete value corresponding to the one of the selected second plurality of ranges; and if it is determined that the input value is not in any one of the selected second plurality of ranges and thereby corresponds to a second discrete value having an output occurrence rate lower than the selected occurrence rate, determine an initial range in the first plurality of ranges using the hash table and search for the range in which the input value is included based at least in part on the initial range and the range table.