For example at a grille during the game.
FWIU, e.g. Chromecast have ultrasonic pairing.
The same issue affects radio time signal (e.g. https://en.wikipedia.org/wiki/Greenwich_Time_Signal, last beep is the exact top of the hour), so some broadcasters will no longer play them on internet streams/digital radio, rather than be inaccurate.
Selecting between multiple audible [sports bar TVs, radios] might imply need for a sonewhat-unique signal code, or only over e.g. USB would work with more than one game on; because there's naturally noise in that airgap channel.
Actually, the "Waver" youtube video linked at the top of the README has an embedded ultrasound transmission at around 0:36. I can for example decode the message on my iPhone by simply running the Waver app and playing the video on my PC.
Some people have already done some work for AV sync in the issues of the project [0].
> The I2S is a small, low-cost MEMS mic with a range of about 50Hz - 15KHz, good for just about all general audio recording/detection.
From https://en.wikipedia.org/wiki/Ultrasound :
> Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.
Raspberry Pi Pico (RP2040), Pi Zero [2 W]: $5+
Power supply, case, wall-mount:
Mic: ~$6
Huge [red] 7-segment display with I2C and voltage regulator components taped to the wall next to the sports bar TVs: