Room Acoustics

The Problems with Soundproofing your Home Theater


Soundproofing a home theater is fraught with problems and complexity. It seems like it should be an easy task. Just keep the sound in the one room. How hard can that be? Well, if you’ve ever tried to control water (or a group of cats), you know that something that seems simple usually gets way out of hand. Soundproofing a home theater is the same. While HOW to soundproof a home theater is beyond the scope of this article, some of the issues may help you decide whether or not this is an undertaking that you want to…undertake.

Sound is Like Water

The best way to think about sound in a room, it to envision filling that room with water. All the way to the ceiling. Is there a way for the water to get out? Then there is a way for the sound to escape. And that sound that is escaping from your home theater? That is the sound you are trying to “proof.”

There are two “paths” for sound: Direct and Flanking. A direct path is exactly what you think it might be. An open door, a hallway, or a window. Any opening is a direct path for sound. Block off that path, and you reduce the sound. But there are other direct paths. Is your speaker sitting directly on a hard floor? Have you used carpet/floor spikes with your subwoofer or your speakers? These directly couple (connect) the speaker to the structure of your home. When the speaker shakes, it shakes the structure of your home. This allows a direct path for the sound to transmit through your structure into other rooms.

A flanking path is one that isn’t direct. This might be the space under your door, through your can lights, or around your power outlets. These are ways for sound to also get out of your room and into other spaces of your home. Again, no matter how small the hole, water will find a way out of a container. The same is true with sound.

Author’s Note: Sound energy is reduced when it is forced through a different state of matter. The drivers in your speakers pump back and forth to created soundwaves into your room. When you close your door, the sound has to go through the air of your room, then the solid of the door, and then back into the air of the space on the other side of the door. This is why you may not be able to make out what the people in the next hotel room are fighting about unless you press your ear against the wall.

Like this but with sound.

It’s More Than Room Treatments

When we talk about room treatments, we talk about absorbing sound. That happens because the sound goes from the air through the solid of the room treatments. The fibers in the room treatments transform some of the sound energy to heat. This reduces the amount of sound energy in the room. The problems of controlling bass and reflections in your home theater and soundproofing that same room are not similar. Reducing reflections and bass energy is one thing, keeping all the sound from escaping the room is another.

If you were to line your room, floor to ceiling with room treatments, your home theater still would not be soundproofed. If you decoupled all your speakers as well, the sound would still escape. Would you reduce the volume of the escaping sound? Likely. But it wouldn’t be truly soundproofed. Because there are so many ways for sound to escape. Do you have an AC duct in the room? Sound is getting out that way. Did you cut holes in your walls for speakers or lights? Sound can get out there. To truly soundproof a home theater isn’t just adding room treatments. It’s dealing with sound escaping from every possible egress.

True Soundproofing of a Home Theater is EXPENSIVE

If you are starting to think to yourself, “There is a lot more to this than I thought,” you’d be right. It’s like the time when I was a kid and thought I could make a very tall and thin swimming pool by plugging the drain in the shower. Sure, it was fine until the water reached the door of the shower. Then I had a lot of explaining to do as to why half the house was flooded.

True soundproofing requires that you not only block all direct and flanking paths for sound but to decouple your home theater from the rest of the house. Because true soundproofing means that when you are standing on the other side of the home theater door, you can hear NOTHING coming from inside. Nothing. And that means lots of planning, lots of extra cost, and tons of money.

Usually Need to Start with an Unfinished Room

Retrofitting a room to be truly soundproofed is usually not feasible. You can do a lot to reduce sound transmission to other rooms, but completely eliminating all sound transmission requires a room to be taken down to the studs. For true soundproofing, you need to construct a “room within a room.” This is a construction technique that has all the walls, the floor, and the ceiling of the home theater completely disconnected from the rest of the house. The floor sits on rubber or some other soft material. None of the walls or ceiling is connected directly to the rest of the house. Plus, all those flanking paths we mentioned (HVAC, lights, wall outlets, etc.) need to be somehow blocked from allowing sound out.

And when you finish with all that, you STILL need to acoustically treat your room. Because while you’ve kept the sound from getting out, to get good sound inside your home theater, you still need to control reflections and bass. That requires room treatments, bass traps, and proper subwoofer placement.

Conclusion

True soundproofing is difficult and expensive. But it can be done. We often recommend you spend some time on SoundProofingCompany.com if you want to know more. Reach out to them as well. They are responsive and helpful. They’ll give you options from full soundproofing to sound reduction. Unfortunately, when people run into sound transmission problems in their home theaters, they think throwing up a few absorption panels will “soundproof” their room. Unfortunately, it is so much more than that. If you really want a soundproofed room, save your pennies, do your research, and be prepared to take your home theater down to the studs. Because that’s probably what it is going to take.


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