The present disclosure describes an efficient computer-implemented near-field communication system and method based on broadcasting audio signals for dynamically providing context-related additional content to a mobile device. In embodiments of the present invention, the additional content is mapped to specific audio watermarks and/or triggering commands which are encoded together into a digital signal. Based on continuously scanning the received background noise, an exactly defined frequency range and volume is dynamically selected for broadcasting the signal. Hence, the encoded digital signal is further modulated into an audio signal in the exactly defined frequency range. In embodiments of the present invention, the selected exactly defined frequency range for transmitting the audio signal may preferably be located in the ultrasound and/or infrasound frequency range. In case of transmitting infrasound signals, gyrosensors of the mobile device may be employed as audio signal receivers in embodiments of the present invention. Moreover, in further embodiments of the present invention, audio signal receiver of a mobile device such as gyrosensors or microphones may be switched on by transmitting a command via a wireless network such as Wifi or Bluetooth. Also the information about the selected frequency range and volume for broadcasting the audio signal may be provided to the mobile device via a wireless network in embodiments of the present invention. In response, an audio signal receiver of the mobile device may be tuned to the selected frequency range. The received audio signal is further processed on the mobile device so that the context-related additional content may be displayed and/or rendered.