To provide an acoustic communication system with high reliability and high speed.

A plurality of PN signals are mixed with a musical sound signal, and released. When a volume level of the musical sound signal is low, a phase of each of PN signals is modulated by a data signal, and the data is transmitted by the PN signals in parallel and at high speed. At the same time, when a volume level of the musical sound signal is high, one of the PN signals is transmitted as a PN signal for modulation which is modulated by the data signal, and the other is transmitted as a pseudo noise signal for reference which is not modulated by the data signal. A receiver side calculates and adds correlation values for the PN signal for modulation and the PN signal for reference of the received signals to modulate the data signal based on the added correlation value.