The invention provides a digital hearing-aid unequal-width sub-band 
automatic gain control method. The method includes: designing an unequal-width analysis 
filter bank according to 
human ear auditory characteristics, conducting segment 
processing to input acoustical signals, filtering each segment acoustical 
signal by using the analysis 
filter bank to obtain signals of various sub-bands, counting input 
signal sound pressure level inside the various sub-bands, conducting sub-band automatic 
gain adjustment according to the sub-band 
signal sound pressure level, finally using a synthesizing 
filter bank to synthesize adjusted sub-band signals to obtain 
system output signals. According to the digital hearing-aid unequal-width sub-band 
automatic gain control method, 
noise and voice signals are isolated out through the sub-band filter 
bank, and thus the gains of 
noise frequency ranges and the voice signals are respectively controlled, and the roles of 
noise suppression and signal-to-noise ratio improvement are played. Compared with a traditional equal-width sub-band filter 
bank partition method, an unequal-width filter 
bank sub-band partition method used by the digital hearing-aid unequal-width sub-band 
automatic gain control method coincides with the 
human ear auditory characteristics. On the premise of obtaining the same effect, the amount of sub-bands need parting and the calculated amount are reduced. In addition, the digital hearing-aid unequal-width sub-band automatic 
gain control method is achieved totally by a 
software program with no need of adding an additional hardware circuit, thereby saving the cost, weight and size of a product.