What is the phenomenon where sound waves bounce off a surface called?

What is the name of the phenomenon where two waves combine to form a single wave?

What is the name of the phenomenon where a sound wave spreads out as it passes through an opening?

What is the name of the phenomenon where a sound wave changes direction as it passes through a medium?

What is the name of the part of the ear that collects sound waves?

The sound created in a big hall persists because of the repeated reflections. The phenomenon is called