If the parabola is closed off by another curved surface, it is called an ellipse. Sound will travel from one focus to the other, no matter where it strikes the wall. A whispering gallery is designed as an ellipse. If your friend stands at one focus and you stand at the other, his whisper will be heard clearly by you. No one in the rest of the room will hear anything.
Reflection is responsible for many interesting phenomena.
Echoes are the sound of your own voice reflecting back to your ears. The sound you hear ringing in an auditorium after the band has stopped playing is caused by reflection off the walls and other objects. A sound wave will continue to bounce around a room, or reverberate, until it has lost all its energy. A wave has some of its energy absorbed by the objects it hits. The rest is lost as heat energy.