If you concerned about sounds entering or leaving your living room, heavy curtains are an ideal acoustical treatment. Opt for materials like velvet, silk or brocade, which are thick, substantial fabrics. These types of curtains actually absorb sound, particularly at speech frequency, so covering your windows with them helps block exterior sounds and conversation from entering your living room. If you don't like the idea of being stuck with heavy curtains all the time, pair them with sheers so you can open the heavier curtains when noise isn't an issue while still maintaining some privacy.
While hardwood floors add an attractive, decorative element to your living room, they can also wreck havoc on acoustics. Sound easily bounces off the hard, smooth surface and becomes distorted before it reaches your ears. However, adding carpet to the floor provides a soft material where sound isn't likely to bounce off; carpet also absorbs some errant noise, as well. Combine the carpet with a soft pad to provide extra protection against sound reflection. If you aren't a fan of wall-to-wall carpeting, invest in a large, plush area rug that you can place in the center of the room to cover as much of the wood floor as possible.
Another acoustical treatment you can use in your living room are canvas absorbers. As the name implies, they are made from pieces of canvas and mounted to the wall with foam-backing behind them. Like curtains and carpeting, the canvas absorbs sound so it is less likely to enter or leave your living room. The best thing about these absorbers is that you can use canvas artwork to make your own, so you can actually add a decorative element to your walls while improving acoustics at the same time.
If you want ideal acoustics for your living room, invest in some diffusers and bass traps. Diffusers help scatter sounds throughout the room to prevent echoes and other sound irregularities. You can purchase prefabricated diffusers, but their design is often unappealing from a decorating standpoint. However, architectural details like pillars and columns can work as diffusers, too. Even a large bookcase can do the job. Bass traps improve acoustics by absorbing low-frequency sounds. Place them in the corners of your room to ensure that all errant sounds are absorbed.