I don't think air-gapped audio transmission could ever reach a fast and reliable transmission so that it allows transferring files in reasonable amount of time over reasonable transmitter-receiver distances. It's just too many hardware and physical limitations for this approach.

Having said that, I am actually working on a small library for data-over-sound which can be used for small data chunk transmissions across the room [0].

[0] https://github.com/ggerganov/ggwave