A method of playing audio content to a viewer in synchronization with a video content. The method comprises receiving and digitizing an ultrasonic signal comprising ultrasonic synchronization signal(s), the ultrasonic synchronization signal(s) comprising a timecode-carrying part that encodes a respective timecode through modulation of ultrasonic carrier signal(s), the ultrasonic synchronization signal(s) comprising further an ultrasonic marker signal conterminous with the timecode-carrying part. The timecode-carrying part is identified based on a received ultrasonic marker signal and decoded to determine the corresponding timecode. The stored audio content is played back from a playback point determined based on the timecode.