Comment by nurple

Yeah, true. They've made some pretty impressive perceptual voice codecs that take very little data, and using that as the carrier for transmitting data would eat into that quite a bit more. Though, I find steganographic methods quite fascinating and often catch myself pondering ways to exchange data privately where efficiency is a small aspect of the overall goal of the communication channel. I suppose "thought experiment" is a good description.

The most effective/efficient way to do E2EE voice is definitely to use an app that supports voice and transfers via the data channel.