TRANSMITTER, RECEIVER, TRANSMITTING METHOD, RECEIVING METHOD, COMMUNICATION SYSTEM, COMMUNICATION METHOD, PROGRAM, AND COMPUTER-READABLE STORAGE MEDIUM

To provide a technique for making it possible to perform proximity communication using an apparatus not including a special proximity communication device. Transmission data is acquired. Output sound data of a PCM format obtained by encoding the transmission data is output, the output sound data indicating sound in an inaudible frequency band. A DA converter is caused to convert the output sound data, whereby a speaker is caused to output sound corresponding to the output sound data. The output sound data indicates sound having a plurality of sections with sound and soundless sections between the adjacent sections with sound according to the transmission data and that the output sound data indicates a sine curve in which the amplitude of the sections with sound increases from a start time and decreases after reaching a maximum.