The hearing aid device is a 4 X 10 X 15 cm box. It is battery operated and monitored by a PC computer. The Texas 320C25 microprocessor performs real-time signal analysis at 16 kHz and gives 16 energy levels ranging from 0 to 8 kHz by Fourier transform. For each frequency band, the energy received is multiplied by a gain determined according to the patient's audiometric characteristics stored in the device's memory. The signal is then synthesized by reverse Fourier transform and sent to the earphone. The performances of this device are discussed and compared with present hearing aid devices.