Comment by awelkie

You could do something smarter with error correcting codes. Using a rateless code you split your message into an infinite number of chunks, then send these chunks out on your multiple paths, and then once enough chunks have been received you ACK each path. No bandwidth wasted.

I think specifically with voice it should be possible to send two chunks such that if they both arrive then you get your audio, and if only one arrives then you still get your audio but at a lower quality.