Place rugs down first to absorb the sound that reflects from the floor. Use shag rugs or other rugs with a fur-like quality.
Diffuse the reflection from side and back walls by hanging carpet and draperies from walls. Hang these sound absorbers behind the source of the sound as well as on side walls.
Use bookshelves, storage cabinets and media racks to reduce acoustic noise. These complicated spaces diffract sound waves.
Place sound-absorbent materials so that the front of the sound source touches the surface holding the sound-absorbent material. Make sure the edges line up. This diffuses the refraction of the sound waves from off the wall behind the source. Construct a wood board with carpet over it for this purpose.
Use manufactured sound-absorbent pads (see Resources). These are sturdy, porous and durable. Choose the size pads that are needed and surround the source of sound with them.