A coding apparatus comprising: a core coding section adapted to encode transform coefficients in a band lower than a reference frequency among input signal transform coefficients obtained by transforming an input signal comprising sound-related data from a time domain to a frequency domain to generate encoded low-band transform coefficients; and an extension-band coding section adapted to encode transform coefficients in an extension band by using core encoded-and-decoded low-band transform coefficients obtained by decoding the encoded low-band transform coefficients, the extension band being a band higher than the reference frequency, wherein the extension-band coding section comprises: a threshold calculation section adapted to calculate, for each of extension-band subbands obtained by splitting the extension band, a threshold based on statistics on transform coefficients included in the subband; a representative transform coefficient extraction section adapted to compare, for each of the extension-band subbands, an amplitude of the transform coefficients with the threshold to extract a transform coefficient having an amplitude larger than the threshold, as a representative transform coefficient, wherein the transform coefficients are Modified Discrete Cosine Transform, MDCT, coefficients, and wherein the representative transform coefficient extraction section is configured to extract an MDCT coefficient, when an absolute value of the MDCT coefficient is greater than the threshold; and a matching section adapted to calculate, for each of the extension-band subbands, a value of correlation between the representative transform coefficients and normalized core encoded-and-decoded low-band transform coefficients and to select a subband having a largest value of correlation in the band lower than the reference frequency, characterised in that the threshold calculation section is adapted to update, when a number of the representative transform coefficients extracted by the representative transform coefficient extraction section is less than a predetermined number, the threshold in accordance with how many more representative transform coefficients are to be extracted to obtain the predetermined number; and the representative transform coefficient extraction section is adapted to perform processing to again extract another transform coefficient by using the updated threshold. a core coding section adapted to encode transform coefficients in a band lower than a reference frequency among input signal transform coefficients obtained by transforming an input signal comprising sound-related data from a time domain to a frequency domain to generate encoded low-band transform coefficients; and an extension-band coding section adapted to encode transform coefficients in an extension band by using core encoded-and-decoded low-band transform coefficients obtained by decoding the encoded low-band transform coefficients, the extension band being a band higher than the reference frequency, wherein the extension-band coding section comprises: a threshold calculation section adapted to calculate, for each of extension-band subbands obtained by splitting the extension band, a threshold based on statistics on transform coefficients included in the subband; a representative transform coefficient extraction section adapted to compare, for each of the extension-band subbands, an amplitude of the transform coefficients with the threshold to extract a transform coefficient having an amplitude larger than the threshold, as a representative transform coefficient, wherein the transform coefficients are Modified Discrete Cosine Transform, MDCT, a threshold calculation section adapted to calculate, for each of extension-band subbands obtained by splitting the extension band, a threshold based on statistics on transform coefficients included in the subband; a representative transform coefficient extraction section adapted to compare, for each of the extension-band subbands, an amplitude of the transform coefficients with the threshold to extract a transform coefficient having an amplitude larger than the threshold, as a representative transform coefficient, wherein the transform coefficients are Modified Discrete Cosine Transform, MDCT, coefficients, and wherein the representative transform coefficient extraction section is configured to extract an MDCT coefficient, when an absolute value of the MDCT coefficient is greater than the threshold; and a matching section adapted to calculate, for each of the extension-band subbands, a value of correlation between the representative transform coefficients and normalized core encoded-and-decoded low-band transform coefficients and to select a subband having a largest value of correlation in the band lower than the reference frequency, characterised in that the threshold calculation section is adapted to update, when a number of the representative transform coefficients extracted by the representative transform coefficient extraction section is less than a predetermined number, the threshold in accordance with how many more representative transform coefficients are to be extracted to obtain the predetermined number; and the representative transform coefficient extraction section is adapted to perform processing to again extract another transform coefficient by using the updated threshold.