The present invention relates to a hearing aid with means for decorrelating input and output signals, comprising a microphone for converting sound into an audio input signal, a hearing loss processor configured for processing the audio input signal in accordance with a hearing loss of a user of the hearing aid, a receiver for converting an audio output signal into an output sound signal, a synthesizer configured for generation of a synthesized signal based on a sound model and the audio input signal and for including the synthesized signal in the audio output signal, the synthesizer further comprising a noise generator configured for excitation of the sound model for generation of the synthesized signal including synthesized vowels.