Provided is a hearing aid system including: a first processor that fast Fourier transforms N input signal tone data output from an input buffer memory, and then executes nonlinear compression; a second processor that inverse fast Fourier transforms amplitude spectrum data; an output buffer memory that stores the voice signal tone data, until the number of the voice signal tone data is N; and a digital-to-analog (D/A) converter that converts the digital voice signal tone data into an analog signal, to then output the analog signal to a receiver. Thus, certain ambient noise due to an acoustic feedback signal and a narrow frequency band that occur in a hearing aid is removed, to thus reduce discomforts due to the acoustic feedback noise of the hearing aid for hearing aid users, and to thereby significantly improve speech discrimination.