This invention employs a scheme to extract, from components within a plurality of blocks obtained by subdividing an input signal with respect to time and frequency, every respective blocks, a component or plural components in order of magnitude of components within the respective blocks to determine, on the basis of a difference between magnitudes of components of respective blocks except for the extracted components and magnitudes of the extracted components, a bit allocation ratio to the respective blocks to quantize components of respective blocks on the basis of the bit allocation ratio thus to generate compressed data, thereby making it possible to realize a technique of allocation of bits desirable also from a viewpoint of the auditory sense with respect to such an input signal including, e.g., overtone to much degree. Accordingly, it is possible to carry out efficient compression/expansion of high sound quality from a viewpoint of the hearing sense. In addition, data recording medium adapted for recording therein data compressed by the digital signal processing apparatus of this invention can more effectively utilize memory capacity as compared to the conventional data recording medium.