This invention relates to a system (100) for controlling gain function of a hearing aid. The system (100) comprises a microphone (102) converting a sound pressure to an input signal, a speaker (112) converting an output signal to a processed sound pressure, and a signal processing means (106) interconnecting the microphone (102) and the speaker (112) and processing the input signal to the output signal according to a control signal. The system (100) further comprises a signal analysis means (108) connecting to the microphone (102) and to the signal processing means (106) and comprising a controller means (124) generating the control signal based on detector means (128, 130, 120) responses to the input signal.