I’d love to understand, in a real world test, if the modified sounds waves would then bounce off nearby walls and end up echoing back anyway, thus nullifying any utility of the discovery.

oh wow, this is like an RF Circulator - https://en.wikipedia.org/wiki/Circulator - which are wacky enough in themselves.

> three- or four-port device that only allows a microwave or radio-frequency (RF) signal to exit through the port directly after the one it entered

Perhaps only superficially related (IANAElectricalEngineer) but that makes me think of multi-phase mercury arc-rectifiers.

https://en.wikipedia.org/wiki/Mercury-arc_valve