A signal processing method for processing a signal, wherein the signal is an audio signal or a speech signal, the signal processing method comprising: selecting the first M sub-bands from N sub-bands, wherein the N sub-bands are obtained by dividing spectral coefficients of a current frame of the signal and are arranged in ascending order of frequency bands; determining, according to an energy characteristic and a spectral characteristic of the M sub-bands, to perform a modification operation on original envelope values of the M sub-bands; performing modification on the original 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 original envelope values of the other K sub-bands of the N sub-bands, wherein N is a positive integer greater than 1, both M and K are positive integers, and the sum of M and K is N; characterized in that the step of determining, according to an energy characteristic and a spectral characteristic of the M sub-bands, to perform a modification operation on original envelope values of the M sub-bands comprises: determining the energy characteristic of the M sub-bands according to original envelope values of the N sub-bands, wherein the energy characteristic of the M sub-bands indicates a concentration degree that is of spectral energy of the current frame of the signal and that is on the M sub-bands; determining the spectral characteristic of the M sub-bands according to the original 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 determining, when the energy characteristic of the M sub-bands falls within a first range and the spectral characteristic of the M sub-bands falls within a second range, to perform the modification operation on the original envelope values of the M sub-bands. selecting the first M sub-bands from N sub-bands, wherein the N sub-bands are obtained by dividing spectral coefficients of a current frame of the signal and are arranged in ascending order of frequency bands; determining, according to an energy characteristic and a spectral characteristic of the M sub-bands, to perform a modification operation on original envelope values of the M sub-bands; performing modification on the original 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 original envelope values of the other K sub-bands of the N sub-bands, wherein N is a positive integer greater than 1, both M and K are positive integers, and the sum of M and K is N; characterized in that the step of determining, according to an energy characteristic and a spectral characteristic of the M sub-bands, to perform a modification operation on original envelope values of the M sub-bands comprises: determining the energy characteristic of the M sub-bands according to original envelope values of the N sub-bands, wherein the energy characteristic of the M sub-bands indicates a concentration degree that is of spectral energy of the current frame of the signal and that is on the M sub-bands; determining the spectral characteristic of the M sub-bands according to the original 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 determining, when the energy characteristic of the M sub-bands falls within a first range and the spectral characteristic of the M sub-bands falls within a second range, to perform the modification operation on the original envelope values of the M sub-bands. determining the energy characteristic of the M sub-bands according to original envelope values of the N sub-bands, wherein the energy characteristic of the M sub-bands indicates a concentration degree that is of spectral energy of the current frame of the signal and that is on the M sub-bands; determining the spectral characteristic of the M sub-bands according to the original 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 determining, when the energy characteristic of the M sub-bands falls within a first range and the spectral characteristic of the M sub-bands falls within a second range, to perform the modification operation on the original envelope values of the M sub-bands.