This is a javascript binding for libquiet, a library for sending and receiving data via sound card. It can function either via speaker or cable (e.g., 3.5mm). Quiet comes included with a few transmissions profiles which configure quiet's transmitter and receiver. For speaker transmission, there is a profile which transmits around the 19kHz range, which is essentially imperceptible to people (nearly ultrasonic). For transmission via cable, quiet.js has profiles which offer speeds of at least 40 kbps. There is also a live example you can use at https://quiet.github.io/quiet-js/.