Abstract: A hearing aid including a hearing aid housing in which is arranged a transmitter unit for transmitting signals containing information to a receiver unit which is outside of the hearing aid. The transmitter unit generates an optical signal in the visible or outside of the visible spectral range and includes a signal generator for generating the optical signal and a modulator for modulating information onto the optical signal. The hearing aid housing includes a signal exit window that is transparent to the optical signal and through which the signal penetrates. The signal exit window has an entrance surface facing the inside of the housing through which the signal enters into the signal exit window, and an exit surface that matches the external contour of the hearing aid housing through which the signal exits from the signal exit window.