A spread spectrum based audio frequency communication system at least includes a transmitting apparatus. The transmitting apparatus includes a first dot-product module, a summation module, a transmitting modulation module, a mixture module, a digital-to-analog converter, and a transmitter. The first dot-product module is configured to perform a dot-product of a first data and a first pseudo-noise code, and derive a first spreading data. The summation module is configured to sum up the first spreading data and a second spreading data to form a summed data. The transmitting modulation module is configured to vary a carrier signal with the summed data to form a modulated signal. The mixture module is configured to mix the modulated signal and an acoustic signal up to form a mixed signal. The digital-to-analog converter is configured to convert the mixed signal into acoustic waves. The transmitter transmits the acoustic waves.