Thick, soft fabrics and other materials often offer excellent sound absorption, so placing carpet or thick drapes along walls can reduce the amount of sound that enters or exits a room inexpensively. Focusing on the doors and windows can help as well.
There are a number of products designed specifically to absorb sound, but thick fabric offers excellent results at a lower price point. It's not always necessary to soundproof the entire room, as all sound-absorbing material on the walls prevents it from reflecting throughout the room.
For more thorough soundproofing, spray foam is a viable choice. This foam goes under the wall, and it lets homeowners achieve better results without changing the look of their room. Using spray foam requires cutting through the wall and patching it once the spray foam is in place, so it might be wise to ask for help. Spray foams can also improve a room's insulation and help homeowners cut back on heating and cooling bills.
Doors can leak sound through gaps, so one of the most effective ways to improve a room's sound isolation is to install a door bottom that closes this gap. Windows are another potential culprit of sound leakage, and caulking the gap around the window to ensure full coverage can improve the room's sound isolation.