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.

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.

Absorbing NoiseAbsorbing

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 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.

BlockingBlocking Noise

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 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.

Echo...Echo..….Echo….…..Echo…...…..Echo

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.

Now what?

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:

  1. Are you looking to block sound or absorb echo?
  2. What are the dimensions of and surfaces in your room?
  3. 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)
  4. 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:

  1. Fabric wrapped acoustical panels
  2. Sonex Classic acoustical foam panels
  3. Wallmate stretch wall system

Here are few sound blocking products:

  1. Soundbreak XP soundproof sheetrock
  2. Mass loaded vinyl barrier also known as MLVB
  3. RSIC-1 Clips resilient sound isolation clips
This entry was posted in Reducing Echo, Soundproofing and tagged , , by Ted W. Bookmark the permalink.
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About Ted W

My name is Ted Weidman. During my time at Acoustical Surfaces, Inc. I have helped countless people with all kinds of different noise problems. I have a background in education, which hopefully helps me explain noise, sound, and acoustics in a way that is easy to understand.

Please contact me with any questions you may have.

direct: 952.466.8225 | office: 800.527.6253 | fax: 952.448.2613

289 thoughts on “Soundproofing vs Sound Absorbing – What’s the Difference?

  1. I just built an aquarium in a cabinet, complete closed in with doors. With the doors closed, the aquarium equipment is making too much noise. I want to reduce the amount of noise coming out of the cabinet…any suggestions?
    I thought about buying the studio foam (one with ridges or egg crate) and lining the inside of the cabinet. Will this be a good solution? I think you said this is an absorption not a soundproofing strategy. I don’t need it completely quite, just need the sound reduced by say 50%. Thank you.?

    • Your initial thought about lining the inside of the cabinet is definitely a good starting point. I would get something in there and take a step back and listen. You may want to look into a cut-piece of our 1″ or 2″ Quiet Liner. This could be a more economical option than foam and will possibly outperform foam.

      If it is still an issue, use some weather stripping and seal up the joint between the doors and the cabinet to try to make them airtight.

      Hope that helps!
      Ted

  2. I live in basement of my parent house that has drop selling and have a 5 year and a 1 year old children. I am completely tired of my parent running down every time anything happen to see why my kids are crying. what suggestion do you have for me to help my noise not be heard upstairs?
    Thank you Mo.

    • Soundproofing drop ceilings can be difficult – especially when the downstairs and upstairs share common HVAC duct work.

      I would back the ceiling tiles with 5/8″ sheetrock as a first step. I would also get up into the ducts that supply air to the downstairs room. If at all possible, increase the duct size, for example, from a 6″ round duct to an 7″ round duct and introduce a minimum of one 90° bend per supply and return line. I would then line the inside of the ducts with our 1″ Quiet Liner and close the system. That should significantly reduce the amount of sound that is heard upstairs.

      Thanks,
      Ted

  3. Greetings Ted,

    Previously I’ve seen a home theatre/gaming setup with the bass drivers set into a platform under the couch. The basic platform was made of 2×4′s and 1/2″ plywood approximately the same size as the base of the couch and about 4″ high, so basically a big speaker box for the subs, pointing up to the bottom of the couch.

    How could a similar platform be constructed for an upper floor room to minimise the amount of sound conducted through the floor to other rooms below? I would want to either keep it low (in the 4″ range) or make the base big enough for people sitting on the couch to use the platform as a rest/floor.

    Cheers. :)

    • To be very straightforward, the answer to this question about how to build a subwoofer box that will minimize the sound that gets through the floor and the spaces below is – it can’t be accomplished.

      If you have a subwoofer upstairs and it is loud enough to be enjoyed, it’s going to be heard – and proably felt – downstairs. That’s just the nature of the beast when it comes to low frequencies. If someone has a subwoofer in their car, you can hear and maybe feel it a quarter mile away. If you put that same subwoofer within 20-30′ of someone, it would take a floor/ceiling assembly that was 5-8′ thick to start to reduce those types of noises.

      Sorry, but that is a really challenging situation. I would suggest a really good pair of headphones.

      Thanks,
      Ted

      • Hi Ted,

        Many thanks for the quick reply. Your answer is what I was afraid of. :/

        The previous versions I’ve seen were all on ground floors (ie concrete slabs) where there weren’t any worries about noise, or in homes with dedicated home theatre rooms with full insulation and (usually) few/no other people around when the room was in use.

        I was thinking about something that could be used in a multi-family building environment, but alas. Headphones work for as many people as there are jacks, but not so much for a group.

        Back to the drawing board…and maybe a judicious use of scheduling and volume control when others are around. :)

        Many thanks,

        Scott

  4. Hi Ted,

    When I build my apartment, I put sonopan sheets under the sheetrock to prevent sound from going to the other apartment. Unfortunately that’s not enough. Even when speaking at normal levels, the neighbors can hear. We have a large picture on the wall, can I add sound absorbing panels behind it to reduce the amount of noise transferred to the other apartment? (I want to keep the noise in the room)

    • Soundproofing only part of the wall will not offer you any reduction. Sound pressure finds the path of least resistance. So in your case, the sound would just go around the picture. You would need to add a layer of drywall or do some construction to the common wall. We have a few different ways to do that, but in apartments or other rental spaces, doing construction isn’t usually an option. If you would like my recommendations on any of those, just let me know.

      Thanks,
      Ted

  5. I have a 10feet x20 feet Closed Hall (Double door) but there is lot of echo in the room. I want to use this room as a indoor video recording studio. Pls suggess me…

    • I would be happy to start to make some recommendations, but I need to get quite a bit more information from you. Could you please send me some photos of the space as well as the height of the room? Your address or location would help in determining costs, as well. “Recording Studio” acoustics are often much more of a specific approach than just “reducing the echo” in the room, and like people, most studios are unique and should be approached as such. What may work well (or be the best recommendation) in this studio might be the wrong product for that studio.

      Thanks,
      Ted

  6. Hello,
    I’m considering a lease for an indoor cycling studio and I’m interested in your recommendations for sound proofing. The space is on the second floor of a 2 story commercial building consisting of a large area which we would break into a studio and a lobby. We ran a test blasting a boom box and you can hear noise below. Faint, though you can definitely hear it when it’s quiet. I have an excellent contractor I’m working with but I also wanted to ask your opinion on how best to sound proof. This is a very good location so I’m willing to pay for high quality, effective materials. We would be renovating the space and would therefore have the opportunity to construct whatever is needed.

    The studio space is ~850 sq feet, there will be up to 35 bikes. The lobby is 350 sq ft.

    As part of the solution I would be interested in controlling the room for reverberation, but first and foremost the main issue is soundproofing. Thank you very much!

    • It’s going to be best if you and I spend a few minutes on the phone to discuss this one. At this point, I can’t tell if you are looking to stop an impact-type noise or airborne-type noise from music being played (or both).

      Thanks,
      Ted

  7. hello,
    I have a big problem with pump, fan and a high pitch noise all which penetrate from outside of my fifth floor apartment into the open space within. Although i am on the firth floor i am surrounded by the outside walls of close buildings. There are 5 floors above me. I do not have a balcony but can get out of my window and stand on the floor which joins all of these buildings together. To illustrate essentially i am in a valley of walls (my apartment is the only one like this as the others look out to sky and city). The building in front of me which is 2 yards from my window is the projection room of a theatre. and above that is the roof of the theatre. The noise comes from within the building not on the roof where the big industrial airconditoning units are. The noise particularly from the pump vibrates through the thick concrete wall, floor and thin window glass into my ears and makes me fell nauseous, cant sleep at night and gives me anxiety. Can you help me as it is all driving me mad as it is a 24/7 thing but the pump is constant but ranges in loudness depending on how it is laboring.. The noises are similar to refrigeration noise but on an industrial scale. Cant wait to hear from you.
    Regards Patricia

    • The cheapest and easiest fix would be to just move. Reducing sound – especially from structure-borne vibration energy – can be extremely involved. Essentially, you have to get whatever machine is running and causing the vibration onto spring isolators so that is allowed to move without introducing the energy into the structure.

      You might get some reduction of the airborne sound coming into your apartment by installing a Climate Seal Window Insert over your existing window.

      This just sounds like a very bad living situation with a lot of different things going on – and as a practical approach, finding a space that has problems/issues that are more manageable will be the best, easiest, and cheapest way to proceed.

      Thanks,
      Ted

  8. Hello,
    Thank you for your article.
    I just moved in to a new apartment and the first night I was awakended by the huge noise from four A/C units below my window (I’m on second floor and they are on ground). The sound is likely to be caused by the vibration of those machines and it’s sort of like the roar of car engine. I was greatly affected by this noise and I can’t get to sleep ecery night. I’m also thinking of using soundproof material to block the noise and I have tried thick curtain, which doesn’t work at all. I see lots of soundproof material online but I’m really not sure which one is more effective for my situation. I have read your article and thought it to be really helpful. So I’m asking for some advise from you about how should I block the noise outside my window?( my window is 6ft*6ft and four A/C units are right below my window)
    Really thank you for your attention!

    • Are these machines introducing a structure-borne vibration energy into the building, or is the airborne sound causing your windows to vibrate? Have you discussed the problem with the landlord? The most effective way to reduce the noise is to get some kind of line-of-sight enclosure around the machines – but this treatment is intended to reduce airborne noise. Structure-borne vibration is a whole different story.

      Thanks,
      Ted

  9. Hi, I got a pair of speakers & when place at one end of the right corner wall, the bass is louder then the left when it is against a normal wall & close to an opening door. I did move the right speaker out a bit but the bass is bloomy. Can I put some thing on the side or cover with sound absorbing & proofing (I don’t mind covering it up) on the right speaker so that it can minimize the reflected sound ?

  10. We are getting a new fridge because our old one is too noisy and we will use it in the garage. The new fridge will go in an alcove which is plywood on one side and cabinets above and on the other side. Line the space with absorbing material? How about the hardwood floor?

    By the way, the ASI page on “quiet liner” has a typo, “Excellent Noise Absortion.”
    Thought you’d like to know.

  11. Hello,

    I live in an old Victorian terraced house in London and have been told by our neighbours that they can hear “normal level conversation” through our walls – in some patches more than others, and perhaps where fireplaces once were (we believe the original fireplaces were removed many years ago).

    The strange thing is, we can barely hear anything from our side – just the occasional bit of loud TV and raised voices if and when the neighbours shout. My first question therefore is – are my neighbours overly sensitive?! We keep our voices down and are generally quiet – but apparently we can still be heard when just chatting in our bedroom (not a very relaxing thought). On the other hand, we can hardly hear a thing… Is it possible for the sound travel to only be problematic in one direction?!

    The neighbours have asked us (a few times) if we would consider sound proofing. We have looked in to it, but it sounds relatively costly and invasive (we could need to strip of skirting boards, coving and repaint etc). Is there anything else we could do? I wondered about acoustic panels but now understand they are for something else entirely (v useful blog post!).

    Alternatively, I kind of feel like if we can’t hear any noise from next door, then the onus really should be on our neighbours to fix the “problem” from their side… Why should we pay to fix a problem we’re not experiencing?!

    Would really appreciate your technical insight into the issue – specifically, how can it be that they’re experiencing something we’re not through the same wall?!

    Many thanks,

    • I’m sorry to hear you are having noise issues. It is impossible for me to speculate about your neighbor’s sensitivity, but you could be correct. They may be very quiet people living in a very quiet space, so even slight noises could be heard easily by them. Sound travel is not one-directional – if sound can leak from “room A” to “room B”, it can equally leak back from “B” to “A” – the difference, however, would be the ambient noise (background noise) difference in the rooms and the listener’s sensitivity to sound.

      Blocking or reducing sound from one space to another is something that is very very specific to the construction of the building. It is very difficult for me to try to make valid recommendations without knowing exactly where the sound is leaking. I would suggest getting together with your neighbors and putting a constant noise source (like a radio) in each particular room on your side (one room at a time) and going to your neighbor’s place and listening. Your ear should be able to tell you where the sound is the strongest (and the leak is the worst) and depending on the details there, you could make appropriate changes to the space.

      Sorry I am not able to offer steps to fix or reduce the problem, I simply don’t have enough information to make recommendations.

      Thanks,
      Ted

  12. Hi Ted,

    Thanks for the blog!

    I have a basement area that will be soundproof (walls, ceiling, floor), except for a stairwell.

    There is a big, heavy door at the top of the stairwell. I’m pretty sure if I make it airtight, that will cut down the sound, but I’d like to do more, if possible.

    If I add sound absorption panels along that stairwell, will it reduce sound to the rest of the house, by absorbing it before it gets there? I know the sound has to reverberate up the stairwell because there is no line-of-sight from the top of the stairway to the source of sound.

    I know this is not perfect, but will panels help at all? If so, where should I focus? One wall and the ceiling? The corners? Spots in the stairwell where I can see the source of sound?

    Thanks again!

    Jay

    • There is nothing wrong with sealing up the door at the top of the stairs and stepping back and listening to asses the need. You could always come back and add panels in the stairway if you experienced a lot of sound pressure in the stairway and had more sound than you want leaking out of the door at the top.

      Installing sound panels in the stairway is simply going to reduce the echo/reverberation/sound pressure in the area. This is likely to yield less sound on the other side of the door, but the door and seals will be doing most of the work. Placement of the panels in the stairwell isn’t as critical as the overall square footage installed and the thickness of the panels – relative to the nature of the problem. Sound simply travels too quickly for the location of the panels to make an overall difference of the echo/reverberation – so if it looks better to have the panels on the ceiling, go for it. If you prefer them on the walls – awesome.

      Please let me know if you have any further questions. Thanks,
      Ted

  13. I have a small problem in that my Blendtec blender is waking my neighbor when I make my daily breakfast. Is there something out there that I can use to absorb the noise? I am thinking about making a box to encase the blender when it is on. Or if you have any other suggestions I am game to here them and try it.

    • This is a bit of a unique request. I don’t use blenders, myself, but I can make some speculations that should help.

      I would start by putting the blender on our Super W pads to absorb the vibration energy of the blender from getting into the counter.

      If the airborne sound of the blender running is also a problem, you could build a box out of plywood or MDF board and line the inside of the box with an absorbent material. There are quite a few different options for what to use on the noisy side of the box. The most effective would be the Echo Eliminator panels.

      Thanks,
      Ted

  14. Hi Ted, Thanks for this post. It’s very informative! We have a situation where our water softener in our garage is on the other side of a bedroom that our newborn is going into. If he’s anything like our daughter he’ll be very sensitive to sound. Even with a white noise machine in the bedroom you can hear when the water softener is regenerating, not to mention when we operate the garage door. If I understand what you wrote here, the sound BLOCKING materials is what we need. With all the plumbing in this shared wall, we cannot redo it to make it a true soundproof wall. If the vinyl barrier was hung on the shared wall in the garage, how significantly would it block the noise into the bedroom? Would foam/sound absorbing materials do any good?
    Thank you!
    Meghan

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