A signal processing method for processing an audio signal or a speech signal, comprising: selecting M sub-bands from N sub-bands, wherein the N sub-bands are obtained by dividing spectral coefficients of a current frame of a signal, frequency bands of the M sub-bands are lower than frequency bands of the other K sub-bands in the N sub-bands, N is a positive integer greater than 1, both M and K are positive integers, and the sum of M and K is N; computing and quantizing envelope value of each sub-band of the N sub-bands; determining total energy of the M sub-bands according to the quantized envelope values of the M sub-bands; determining total energy of the K sub-bands according to the quantized envelope values of the K sub-bands; determining a ratio of the total energy of the M sub-bands to the total energy of the K sub-bands as an energy characteristic of the M sub-bands; determining , in a case in which the energy characteristic falls within a first range and a spectral characteristic of the M sub-bands falls within a second range, to perform a modification operation on quantized envelope values of the M sub-bands, wherein the spectral characteristic of the M sub-bands indicates a degree of spectral fluctuation of the M sub-bands and is obtained based on the quantized envelope values of the M sub-bands; performing modification respectively on the quantized envelope values of the M sub-bands, so as to acquire modified envelope values of the M sub-bands; and performing first bit allocation on the N sub-bands according to the modified envelope values of the M sub-bands and quantized envelope values of the K sub-bands. selecting M sub-bands from N sub-bands, wherein the N sub-bands are obtained by dividing spectral coefficients of a current frame of a signal, frequency bands of the M sub-bands are lower than frequency bands of the other K sub-bands in the N sub-bands, N is a positive integer greater than 1, both M and K are positive integers, and the sum of M and K is N; computing and quantizing envelope value of each sub-band of the N sub-bands; determining total energy of the M sub-bands according to the quantized envelope values of the M sub-bands; determining total energy of the K sub-bands according to the quantized envelope values of the K sub-bands; determining a ratio of the total energy of the M sub-bands to the total energy of the K sub-bands as an energy characteristic of the M sub-bands; determining , in a case in which the energy characteristic falls within a first range and a spectral characteristic of the M sub-bands falls within a second range, to perform a modification operation on quantized envelope values of the M sub-bands, wherein the spectral characteristic of the M sub-bands indicates a degree of spectral fluctuation of the M sub-bands and is obtained based on the quantized envelope values of the M sub-bands; performing modification respectively on the quantized envelope values of the M sub-bands, so as to acquire modified envelope values of the M sub-bands; and performing first bit allocation on the N sub-bands according to the modified envelope values of the M sub-bands and quantized envelope values of the K sub-bands. <EOS>