Hearing aid or hearing aid system with acoustic battery indication

The hearing aid has an input converter (1) for picking up the input signal and converting it to an electric signal. A signal processor (2) processes the electric signal and amplifies it in dependence on its frequency. An output converter (3) outputs an acoustic output signal. A voltage source e.g. battery (4) and means (6) for operating the hearing aid are also provided. The current charge state of the battery is determined from operation of the hearing aid and the hearing aid outputs an acoustic signal representing the charge state. Independent claims also cover a hearing aid system having two such hearing aids.