Abstract: 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.