Understanding Room Acoustics

The basics of acoustics

Acoustics refers to the manner in which sound behaves relative to the surrounding space. For example, outdoor and indoor concert theaters are specially designed to optimize sound. While such spaces typically include enhanced and intricate architectural elements which you're not likely to have in your home, you can still apply the same principles to get the most out of your sound system.

Why Sound Matters

Sound makes a major difference in your perception of a televised program. Crisp, clear, lifelike sound draws you deeper into the action and enhances your viewing experience. If you're really intent on recreating a movie theater feeling in your home, you'll pay careful attention to the orientation of your speakers and the technical aspects of your sound system -- sound is a major reason a scary movie can make you jump out of your seat, or a great moment in a sporting event can make you stand up and cheer.

Acoustics 101

Acoustics is not about the technical qualities of sound, such as treble and bass; rather, its focus is on maximizing the quality of sound within the defined space. You may be limited in what you can do in your home theater, especially if you're setting up a multipurpose room. However, there are several important and basic principles you should observe to make the most of what you have.

First, and most importantly, understand that you need to optimize the effects of both direct sound energy and reflected sound. Here, keep in mind that sound "reflects" every time a sound wave encounters a physical barrier, be it a coffee table, a wall, or a chair. You want to set up your seating so that the direct sound energy coming from your speakers is equal to the reflected sound energy in the room. That means you should eliminate as many reflecting elements as possible; ideally, you'll only want walls to reflect sound. Finding this ideal distance will require some experimentation on your part; there is no universal principle, and it depends heavily on the layout and orientation of the room.

You can also treat your walls with special materials to improve acoustics in a room. Here are some principles to guide you:

  • Cover 20 percent of your walls and ceilings with material that absorbs sound -- it should be at least 2 inches thick and have a density of at least 3 pounds per cubic foot.
  • Cover about 30 percent of the walls and ceilings with sound scattering materials. These should be at least 4 inches deep, but they can be up to 1 foot in depth. Deeper is better.
  • Leave about 50 percent of the room to generate reflected sound.

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