Chirp

Chirp is a data-over-sound protocol: it transmits small data payloads (up to 50 bytes) wirelessly via audible or ultrasonic audio tones using only a device's speaker and microphone.

Chirp is a software-only, device-agnostic protocol for data-over-sound: it converts an array of bytes into a 'sonic barcode' for transmission. The technology leverages standard speakers and microphones to send small payloads (e.g., 50 bytes) over a short range (10-20 feet), operating in either the audible or inaudible ultrasonic frequency range. Unlike Wi-Fi or Bluetooth, Chirp supports one-to-many broadcasting and requires no prior network pairing or internet connection, making it ideal for offline applications like device provisioning, authentication (e.g., Audio Tickets for Shuttl), and gaming (e.g., Activision's Skylanders). The original company, Chirp.io, was acquired by Sonos in 2020.

https://chirp.io/