1. A signal processing method comprising: inputting to-be-processed data including a set of first N-dimensional coordinate values (N: a natural number) in an N-dimensional space and first sampling values at the first N-dimensional coordinate values; inputting search pattern data including a set of second N-dimensional coordinate values in the N-dimensional space and second sampling values at the second N-dimensional coordinate values; setting a set of virtual corresponding points designated by third N-dimensional coordinate values in the to-be-processed data; acquiring, from the to-be-processed data, a plurality of input patterns each including third sampling values within a first range with reference to a corresponding virtual corresponding point of the virtual corresponding points in the N-dimensional space in correspondence with each of the virtual corresponding points, the third sampling values being included in the first sampling values; acquiring, from the search pattern data, a plurality of search patterns each including fourth sampling values within a second range with reference to a corresponding second N-dimensional coordinate value of the second N-dimensional coordinate values in correspondence with each of the second N-dimensional coordinate values; detecting, from the search pattern data, an estimated pattern including one search pattern included in the search patterns and having smaller differences with respect to the input patterns than other search patterns included in the search patterns; setting a plurality of sampling values at first positions corresponding to the virtual corresponding points in the estimated pattern as set sampling values at the virtual corresponding points; and converting a sampling rate of the to-be-processed data using the set sampling values and the N-dimensional coordinate values of the virtual corresponding points.