Hang drapes on the windows. Choose a thick, heavy fabric that will not only reduce echoes, but will also help block out light.
Place a large rug on the floor of the room. Choose a rug that has longer fibers for maximum sound absorption.
Furnish the room with upholstered furniture. If a piece is not upholstered, add a cushion or fabric cover to it.
Place upholstered furniture against large walls and other areas that are especially prone to echoes.
Decorate the walls with fabric wall hangings. Staple a piece of quilt batting to the back of pictures frames.