How to Keep Sound from Bouncing Around

hard surfaces

Hardwood flooring and other solid surfaces can throw the audio from a home theater surround-sound system out of whack.

Hard surfaces can kill home theater acoustics. Use these tips to minimize the distortion.

Jan. 23, 2007 — by .(JavaScript must be enabled to view this email address)

You may love your tile floors and your wood-paneled walls and ceiling. You may envision building a home theater space with granite countertops in the back, or you might simply clad the vertical surfaces with good old drywall. Well, guess what? All those beautiful and hard building materials can be bad for the sound in your home theater. They can make the audio echo, reverberate and sound shrill.

The ideal-sounding home theater would have thick wall-to-wall carpeting and some fabric walls. But that doesn’t mean you have to sacrifice your flooring or wall choices. The latest studies show that reverberations and echoes don’t matter much in small-to-average-size rooms, especially if you have some padded furniture and other soft materials to help absorb excess noise.

Problem #1: Echoes and Reflections
Just as a shiny object reflects light, any hard surface reflects sound. Too many hard surfaces can cause the audio to reflect so much that it creates echoes and reverberations, which make it harder to hear the dialogue in a movie clearly. Spaces like this are often said to be “live” or have a “bright” sound.

Here’s a quick test to tell if your room will have sound reflection problems. Stand in the middle of it and clap your hands. If you hear an echo or slight ringing afterwards, the sound from several speakers will be harsh. You’ll need to add absorptive materials.

Mix it up - Sound reflection is not all bad. All home theaters need some sound reflection, or the audio might never reach your ears. The idea is to have the right mix of reflection, caused by hard surfaces, and absorption, caused by soft surfaces. The Custom Electronic Design and Installation Association recommends that 25 percent of the surfaces in a room be absorptive and 25 percent be diffusive, the latter of which helps to spread the sound throughout a room.

Absorptive materials include carpets, padded sofas and chairs, heavy drapes and curtains. You can often add enough of these to eliminate any echo or reverberation. So although those leather chairs look great, fabric chairs and sofas do a much better job of absorbing unwanted sounds. Spot rugs work well, if they’re large enough to cover the floor of most of the main seating area. Look for rugs or carpets with thick padding.

Diffusive materials are generally uneven surfaces that help spread the sound throughout a room. These are often placed in the back of a room or on the ceiling to help scatter the sound. And while hardly ideal, a hard surface such as a rock foundation wall or fluted woodwork can actually act as a sound diffuser, so don’t be too quick to cover these up.

Problem #2: It Still Echoes & Booms
This is more often a problem in a big room, where the sound has farther to travel and bounce back, thereby taking it longer to reach your precious ears. Hard surfaces like wooden floors and stone and drywall only exacerbate the problem. What to do?

Treat it right - If there is too much reflection in a room, you may need to add acoustic treatments such as padded wall panels. Absorptive panels are sometimes included near the center of the side walls but can also be placed near the front and the back.

If your front speakers are close to the side walls, you may need some absorptive panels there. These panels can hang on the wall, but they should be thick. Often, panels that are 1 inch or less in thickness are not adequate to absorb sound. Thicker panels are often built into a wall and covered with stretched fabric to give a seamless appearance.

Plan ahead - If a lot of acoustic treatments are needed, it’s best to make considerations for them when the plans are being drawn up, because you won’t want to alter your room later. Consult with your audio/video professional about whether you may need extra acoustical treatments in a room. Acoustic professionals can recommend the best ways to eliminate harsh sounds.

Problem #3: Reflections on Video
Your home theater’s TV, video monitor or front-projection screen is susceptible to reflections in your room as well—from light. Any light in the room, even that reflecting off of a screen, can bring certain hues right back onto the screen. Say you want bright-red walls right next to that big-screen and bright-red seats in front of it? The red can actually reflect onto the screen and discolor your image. For this reason, bright colors in your decor are generally discouraged.

Paint it neutral - An all-black room is perfect for video, but who wants to paint a room all black? Choose neutral and muted colors like gray, and your video will look great. Also stay away from shiny wood finishes like polyurethanes, as these will reflect light back onto the screen as well.

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