Is it possible to create a place, where sound, produces by room's environment, is loud in one or several points, but barely audible in other parts of the room?
Although your question seem to focus on shaping the room to influence the sound in it you may be interested in this Ted talk. It is about producing nonlinear sound waves that are only audible in certain spots.
So same outcome with different technique.
Yes, it is. Practically it is never so pronounced like optical foci (cause of characteristic length scales and wavelengths), but it is well-known sound engineering issue in non-rectangular rooms. It generally causes inhomogenous auditory experience and hence it is usually marked as an unwanted phenomenon.