Abstract: Systems and methods for near-field communications with a mobile device are disclosed. In one embodiment, a computer-implemented method for near-field communication may comprise: detecting, by a source device located at a point-of-sale, the proximity of a receiving device; encoding purchase data on an audio signal with one or more ultrasonic frequencies; and transmitting the encoded purchase data to the receiving device, wherein the encoded purchase data is transmitted using a speaker of the source device.