So - a modem?

My washing machine has a version of this. When on a support call you can hold your phone close to the washer and the phone microphone will pick up ultrasound error codes from the machine.

You have to be pretty close for this to work though.

Have techbros just invented the modem?

Reminds me of this app I’ve never used but seen that uses audio to transmit images with something called SSTV:

SSTV Encoder (Image encoder for Slow-Scan Television (SSTV) audio signals) https://f-droid.org/packages/om.sstvencoder/

(And also Robot36, I think one encodes and one decodes)