This happens all the time everywhere, but really is only audible in rooms with almost all smooth unbroken walls. Because otherwise the waves hit uneven surfaces, bounce off in different directions, and the result is the reflections become diffuse. Which is why surfaces deliberately designed to do this are called diffusers.
This never happens in as you say "an open space". So we can cross that one off the list and we are left with, "and my left ear is not as good as I was young."