Soundproofing vs Sound Absorbing – What’s the Difference?
You want to do what?
When someone has a noise problem and doesn’t know what, why, who, or how they begin scouring the internet looking for “soundproofing”. I have been getting a lot of calls lately from these people. They explain to me that they want sound that is being made within the room to stay in the room or they want to keep sound out of their space. We commonly begin talking about the room and the type of noise that we are dealing with in each particular situation.
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A lot of people ask for pricing on “soundproofing foam”, sound absorbing foam, or sound proofing panels. They are sure that foam is the ticket because people have seen “egg crate” foam or other similar products as finish wall treatments in recording studios, on TV shows and in movies. This misconception is incredibly common – so if you are reading this thinking to yourself, “Well, self, doesn’t foam stop sound? Isn’t foam used for soundproofing a room? Everyone knows that, right?” Unfortunately I have to tell you that you are wrong. Foam does not stop sound, foam absorbs echo. Don’t feel bad. There are lots and lots of people out there that share this idea.
There are two sides of the acoustical coin, if you will. There are products that absorb echo within a room and there are products that will block or stop a sound. (There are some panels that will do both. These are generally called composites, but if I get into that now, things will be confusing so I am going to keep it simple.)
You Can’t Build an Aquarium With Sponges
I came up with an analogy that I have found useful in helping people understand this whole idea in a very generic way. Imagine you are building an aquarium. You want to keep the water in, right? I know I do, at least. What do you think will be more effective, glass panels and seals or pillows and sponges? Sound acts very similar to water when you are trying to control it. If you used sponges as the walls, they would fill with water and let all of it through to the other side. Now if, instead, you used thick glass and good seals, that would keep the water in place. Acoustical materials made from soft, squishy things like sponges are going to absorb. Dense, heavy, air-tight glass will block. That is the basics right there. Now you can impress all your friends by knowing this. Let’s dive more into the specifics.
Products that are designed and intended to absorb echo within a room are soft, light, fluffy products. They will generally feel soft to the touch. They are designed to soften up the surfaces within a room and reduce the echo in that space.
I like analogies, I think they help people visualize and relate to an idea, so here goes another one. Let’s say you are finishing a room in your basement. You have installed the studs that will frame the wall and you are to the point where you are ready for sheetrock. Instead of using sheetrock, though, you decide you are going to put up some 2″ thick “egg crate” foam on the studs. Keep in mind this foam has almost no mass or density, it is mostly air. After you’ve got this sound absorption material installed, you tell one of your helpers to go stand on the opposite side of the wall and begin talking. You will be able to clearly hear each other as if there were no wall in front of you.
Products that are designed to block sound from entering or leaving a space are almost always found inside the wall construction. These products are heavy, dense, cumbersome, or designed to decouple the wall so that one side of the wall doesn’t have hard surface contact with the either.
Remember that last analogy? The one in your basement? Let’s go back there. Now, instead of foam this time, you decide it would be a better option to use 9 layers of 5/8″ sheetrock soundproof materials on either side of the wall. Nine layers on the inside, nine layers on the outside. You send your help to the other side again and have them start talking. I would be willing to bet that you can not hear much of what they are saying because you have added so much mass into that wall.
You guessed it, I’ve got another analogy! Let’s head to the gym. It’s currently under construction because they are adding some real nice racquetball courts. Let’s check them out. The room is made out of concrete and is the size of a standard racquetball court – 20′ wide x 40′ long x 20′ tall. The walls of this room are two-feet thick. You clap your hands in the room and the echo seems to go on forever. Let’s have some fun in here. You have, in your hands 100 new super bouncy balls of varying colors. (You must have really big hands.) You throw them in every direction and they keep bouncing and bouncing everywhere through the room. After a few minutes, they eventually stop bouncing and hopefully you remembered to wear your helmet or you may be dealing with a big headache. Now imagine that you brought some 2″ thick foam with you. You line the walls, ceiling and floor. After that is done, you throw the same 100 super bouncy balls. This time when they hit the wall/ceiling/floor they don’t bounce. The energy from the ball was absorbed into the room, more specifically, the foam. A sound wave inside this room is just like that super bouncy ball. It will reflect, or “bounce”, of any hard surface but will be absorbed by a soft surface.
If you made it this far, I congratulate you for making it through my fairly crude examples. My intent was to help paint a picture to help you understand more clearly the general differences between absorbing and blocking sound (soundproofing). I’m sure there are lots and lots of people out there that are excessively smarter than I am who are shaking their heads because I did not touch on the technical side of things – explaining wavelength and frequency, etc. I don’t care. I am trying to simplify things to give those non-technical individuals a basis to begin educating themselves on their noise problem(s).
Of course, you aren’t going to be an expert in acoustics now. This is a start. For your next step, I would recommend finding an expert or at least someone who knows the specific products that you can use for your specific situation.
So, before talking with that person, I would have these questions answered:
- Are you looking to block sound or absorb echo?
- What are the dimensions of and surfaces in your room?
- What is the room used for, what types of sound(s) are you looking to block/absorb?
(a high pitch-squeaky sound, voices, low frequency-bass type sound, all of the above)
- What are your ideas as to the best way to treat the room, where to put product, or how to approach the situation?
I know this is not an all encompassing list, so I will not feel bad when you leave me a comment that I forgot something. In fact, I encourage it.
Here are few sound absorbing products:
Here are few sound blocking products:
- Soundbreak XP soundproof sheetrock
- Mass loaded vinyl barrier also known as MLVB
- RSIC-1 Clips resilient sound isolation clips