A quick and easy sound damper is hang curtain shears around the walls of the room. white gives a very soft feel to the space and deadens sound quite well. No echo.
Another way to kill the echo if the curtains are not enough is to affix the pressed paper flats from egg crates to the walls behind the curtains. The shape of the pressed paper deflects sound in ways that eliminate the nasty hollow sound of a room. This was often used by musicians who wanted to echo-proof their home studios on a budget.