Which waves could be narrow compared to medium where they propagate and be also directional? Except for electromagnetic. My guess is that we know no such waves/mediums, electromagnetic propagate in such a way due to wave-particle duality.
I could not find the answer via google. The question raised in my mind due to idea to test Is there any experimental evidence to support the Terrell rotation? for waves which are slow compared to electromagnetic and we could evidence the effect.