A headphone device includes an electric input terminal for receiving an electric audio signal, an electric energy storage device, and a charging device coupled to the electric input terminal and the electric energy storage device. The charging device is configured to charge the electric energy storage device with electric energy from the electric audio signal. An audio device includes an electric output terminal for outputting an electric audio signal from an audio source of the audio device, and an audio energy supply device configured to generate an additional electric audio signal with a frequency above a first frequency value and/or a frequency below a second frequency value, and to output the additional electric audio signal via the electric output terminal.