Foam Does not Stop Sound from Going Through Walls
To tackle the topic of “how to soundproof”, I thought I should just go ahead and get that out of the way. It is used to stop echoes in a room. The reason you see it in soundproof recording studios is that they have already done things to the walls to block the sound from going through, then lined them with foam to stop the echo. Stopping echo is important, but if your only concern is your neighbor not hearing your subwoofer going through the wall, foam is not going to do anything at all. Wrong tool for the wrong job. Bass traps may sound like a device that traps all the bass from leaving a room, but they do not. They stop standing waves, which add a warbling noise to the bass within the room. Kind of the same situation.
How to soundproof? What stops sound? Heavy things. Layers of heavy things that are airtight. Heavy things that are airtight and dampened so they don’t vibrate or are made to be floppy in the first place so they will never vibrate, and cover 100% of a wall, ceiling, or floor.
Sound is simply just a vibration in a medium, whatever that medium is. If sound is transmitted through air, it has to vibrate a wall and induce a vibration in the air on the other side of the wall — that’s how the sound is getting “through” the wall. My job here is to educate you on what tricks of physics we can use to keep walls from inducing vibration in the air on the other side of the wall.
So if you want more information on how to soundproof and block sound, you may want to read:
- Soundproofing a Wall
- Soundproofing a Garage
- Soundproofing a Floor
- Soundproofing a Window
- Soundproofing a Door
I’m full of analogies. Here is a good one:
If you have a bright flashlight and put a piece of tissue paper in front of it, what happens? You see about the same amount of light intensity through the tissue paper. The tissue paper doesn’t have enough mass to stop the light waves. This is like putting foam in front of a speaker…sound shoots right through. If you put a piece of construction paper over the flashlight, you may see some light, but less. Put two layers of paper and you see even less. Then for grins, put a small air gap between the layers of paper, you will see no light at all. Sound works the same way.
Physics recap: Mass stops wave energy. Increase mass, decrease wave energy propagation. Layers of separated mass stop more wave energy propagation than would an equal mass of one layer.
Floors
Iso-Step® Soundproofing Underlayment
Common complaint of customers that I hear: “I’m trying to stop the sound coming through my ceiling. I can hear them walking around and it’s driving me nuts.”
Analogy: Two kids with some soup cans tie some string between them and then string them across the street to each other’s houses. One kid talks into the can, the other kid can hear his voice in the other can. This is called mechanical-borne sound. Sound is just vibrations in a medium. Remember, the string is denser than air and will more efficiently transmit the sound over a greater distance.
The customer’s problem is that the surface that their neighbor is walking on is mechanically connected to the sheetrock that makes up their ceiling because everything is tightly screwed to the floor joists, and/or glued tight to a concrete slab. All those mechanical connections are the string between the two soup cans in the aforementioned analogy. We have to “cut the string” to stop the noise.
The most effective way to do this is at the floor level upstairs. Use a squishy floor underlayment under the surface they are walking on like IsoStep®. The benefit here, and why it’s more effective than treating the ceiling down below, is because you are arresting the vibrations before they have a chance to work their way into any of the other building structures. Anything we do to the above floor is going to be restraining the sound from flanking down around the ceiling into the walls and whatever else in the building we don’t anticipate.
Ceilings
Green Glue Noiseproofing Compound
That’s not to say treating the ceiling is ineffective, just harder to do. We need isolation clips, and two layers of sheet rock with a damping compound between them like Green Glue to hang from the floor joists or the concrete slab…in effect: A floating ceiling.
Read About Isolation Clip Installation (PDF)
The isolation clips are effectively “cutting the string” between what is being walked on upstairs, and what makes up your ceiling. Now your ceiling has more mass and a layer of damping compound between it. The damping compound is keeping the layers of sheet rock from vibrating.
Sound is nothing more than vibration in a medium. In this example, we have broken the mechanical connection, added mass, and dampened the mass. The ability for the sound upstairs to induce a vibration in the air on the other side of the ceiling is severely mitigated.
Recessed Lighting
Another common complaint is: “But, I want to add canned recessed lighting into my soundproof ceiling”.
NO! You will shoot yourself in the foot by doing that. There is no real way to get around this as of yet because recessed light manufacturers thus far that I know of DO NOT want to risk adding enough mass and air tightness to the backs of their light assemblies for them to be soundproof. Why? This is a major fire hazard. Heat would build up in that little cavity with nowhere to go…and that’s bad.
Why is this bad for your soundproofing? Because a 1% gap in a sound barrier will transmit 50% of the sound energy through it. If you go through all the time and expense of soundproofing your ceiling and then pop six or more holes in it, the whole thing is for nothing. The only thing stopping sound through that recessed light, is the recessed light housing, which is in most cases thin aluminum. Can you rig something to block the sound behind it? You are taking the risk of causing a fire. No matter how you do it, it won’t be as soundproof had you just given up on the idea of the recessed lighting in the first place. A soundproof ceiling needs to be as unbroken as possible. Full Stop.
Resilient Sound Isolation Clip RSIC-1
Concrete Block Walls
They are not as soundproof as you think. They can be filled with sand or mortar to be made more soundproof, but if the building is completed, what you have is some 2″ thick elastic concrete with air cavities within resonating the sound. Basically, the vibrations in the air on one side can pretty easily vibrate the air on the other side of the concrete block wall.
Solution: Isolation clips and two layers of sheet rock with Green Glue between them, over 100% of the wall.
Doors
Doors are tricky. Before I worked in the noise control industry the most I thought about doors was opening and closing them. I have come to find that you could pretty much create an entire Associates Degree course on doors: the ways to hang them, and the ways to soundproof them. I’m going to try to make this as succinct as possible. Doors are the weak link in a wall, it’s where the sound has that 1% gap to be able to travel through. To soundproof a door, you have to increase the mass of the door and make it airtight. That’s about it. The frame is another matter, if it’s a hollow metal frame it needs to be packed with mineral wool, installed, and then caulked at the drywall returns. Real deal pedigreed soundproof doors are going to be in the STC 50 and STC 55 range, meaning they stop 50 dB and 55 dB respectively. These are expensive…in the $3-4,000-dollar range. If that’s what you need and have the budget, then it is what it is. If you don’t have that much sound to stop or it’s not critical enough to justify the expense, you can just swap out your door for a solid-wood-core door, purchased locally, and get one of our door seal kits.
I have tried for quite a while to verbally explain door seal kits. For such a simple thing, it’s very hard to describe one to someone who has never seen one. So, I just made a video, I highly recommend watching this if it applies to you:
As you can see, sound blocking is something of a rabbit hole that is easy to get lost in. I’m usually pretty brief in my blogs and discussions about acoustics. However, soundproofing things is not easy and requires a lot of hard-nosed examination of the situation at hand. Fortunately, at Acoustical Solutions, we have been doing this for quite a while. We rarely get a question we haven’t had to deal with in the past or haven’t successfully treated.
Thanks for reading and I welcome any feedback or questions. I hope this was helpful.
To learn more about how Acoustical Solutions can solve your noise control problems, use our contact form, call one of our Acoustical Sales Consultants at (800) 782-5742, or visit us on the web at acousticalsolutions.com.
“But, I want to add canned recessed lighting into my soundproof ceiling”
Do you know of any LED lights that might be able to fill in the gaps here? Since LEDs don’t generate the heat that older lights do..
Also, what about in-wall or in-ceiling speakers?
James: Yeah, I have been considering revamping that portion of this blog here lately as LED lighting has progressed significantly in just the last couple of years. Apparently Samsung has even figured out a way to make large windows that can double as displays and light sources now. If one must have recessed lights and wants to use some kind of “sound proof box” behind specifically an LED light, then no I dont think you run the same risks of fire as you would with a Halogen light for example. How to go about accomplishing this though, I will leave that to others to figure out because I still hold the opinion that a soundproof ceiling needs to be as unbroken as possible to achieve its maximum potential. In wall and in ceiling speakers will more effectively transmit sound through the sound barrier because they are the sound source and are placed inside the sound barrier, and are being mechanically connected to the barrier itself. Its a catch-22.
James, just to mention it though: Someone may down the road after the space has changed hands (new tenant, house sold, etc) the chance exists that someone may accidentaly unwittingly put an older hotter light source in there. Which isnt your responsibility anymore true, but you have to consider that you may be “booby trapping” some future person. So just food for thought.
After repeated attempts to get my roommates to shut up, I was trying to dampen noises while I’m sleeping. Reading around, a lot of people have this problem. Are there any issues with creating a frame and draping Mass Loaded Vinyl all around my bed (obviously, decoupling my bed from the floor as well)?
I personally save $700/mo living at this apartment, which is about what it would cost for me to build myself, but, what are the sensitivities? I will probably have to tape seams. I’ll need a hefty frame to hold this, I’m not sure ho big of a space I’ll have to get in!
Also, what is ventilation like in sound proofed rooms/areas? This probably significantly compromises the sound
Steve, yes we do get this question every so often. And your last sentence is the main reason we dont have a specific solution for this, apart from soundproofing the room rather than creating a “bed specific” sound-proof-pod. Ventilation is key, and a major sound leak. Could it be done? Probably, but it would literally have to be, from the ground up, a completely engineered and custom built pod of some kind, with rigorous testing and redundancy fail safes, and probably o2/co2 sensors built in…etc. Its just too much liability and the product would end up costing so much after it was all said and done, that it’s just cheaper and easier to soundproof the whole room. Look up Sensory Deprivation Tank, that is essentially what you would want, minus the water and put a bed in there. Anything short of that, ie, just putting some acoustical blankets around the bed, theres too much guess work on whether that would be adequate to meet the customer’s needs acoustically. Im sorry I dont have a better answer for you on this. Our default is always going to be dropping back to the construction of the room itself to block noise.
Ok, Matt. I’m in need of some good advice. Ever since I’ve moved into my condo, I’ve been experiencing horrible footfall noise from above. I’ve tried everything, with little relief. It’s clear that my upstairs neighbor just doesn’t need to be living above anyone. When my upstairs neighbor flooded my condo several years back, I had the ceilings redone, with what I thought at the time was excellent soundproofing measures. Turns out, there is much more information now on the topic of soundproofing a ceiling, when the option exists to not soundproof the floor above. I had insulation put in to the max, and I used Green Glue in between two layers of special soundproofing drywall. Turns out it didn’t work. The resilient channel system was not installed (of which I was unaware). Plus, I still have recessed lighting. I have a suspicion that my HVAC system is transmitting sound at a high rate as well.
Anyways, I cannot undo the mistakes from the past. I am not in a position to rip up my ceilings again. I’ve got to do something, however, in the meantime to get some relief so I can hold on to my condo as the market recovers. My ceilings are also rather low, so I can’t afford to lose any more height than I absolutely need do.
Here is what I am thinking: firstly, I will get rid of the recessed lighting and have the holes plugged up as much as possible. I would like to put some lightweight but effective sound barrier onto the ceiling. Rubber? Mass loaded vinyl? On top of it, I would like to install a resilient sound system while losing the least amount of space. My theory is if I install the sound barrier and then the resilient channel to it, that might work. [This would be on top of the insulation already in the ceiling and the Green Glue in between the layers of reinforced gypsum drywall]. On top of the resilient channels, I’d like to install some ceiling tiles.
Please let me know your thoughts. With having already spent considerable money years back on a soundproofing option which failed, I don’t want to be disappointed again. I’d also like to do this as cost effectively as possible. Thanks in advance.
Elizabeth, I wish I had a cheaper and easier to install answer for you, but the ceiling or the floor above need to be floated. Floated in the sense that they are no longer mechanically connected to eachother, in the same way the two soup cans are connected by the string in the anology in the blog. You have to cut the string. There is no substitution for cutting the string.
I would suggest installing Isolation clips through the existing sheet rock into the joists, installing hat track, installing some R-13 insulation against the previous ceiling between the hat tracks, then install a 5/8″ thick sheet of sheet rock (no canned lights). If you want to go full 9 yards, go ahead and do another layer of 5/8″ sheet rock on top of that with the Green Glue product. Why didnt Green Glue work before? Its not a subsitute for the reslient channel or resilient clips. It just isnt. Once there is a physical and real cutting of the mechanical connection between the rooms, then you can start talking Green Glue because at that point you are blocking airbone noise from the previous ceiling with your *new ceiling* thats hanging in front of the previous ceiling that was letting all the noise through. And Green Glue is very good at blocking airborne noise. Why R-13? It does actually block sound to a certain degree, but its main reason for being there is to stop resonance between the parallel layers of mass (previous ceiling surface, and the new ceiling surface). This treatment will lower the ceiling about 4″ or so, but will meet your expectations for blocking the foot fall noise you are wanting to block and allow you to not have to tear down your existing ceiling.
Really wish I had read this information before installing recessed lights in my apartment, which wasn’t very sound proof to begin with. Now I can hear whenever people talk above me and most likely vice versus.
Is there a way to sound proof the lights without having to tear down my entire ceiling? I’m mostly concerned with airborne noises as I don’t really have a big problem with the neighbor upstairs stomping around all of the time. She does a bit, but not enough to justify the $15-$20k price tag that was quoted by a local sound proofing company to go the whole 9 yards with decoupling and replacing the ceiling and adding 2 layers of drywall and green glue.
I did ask about a cheaper solution and they said I could get an electrician to install the Quiet Boxes around my recessed lights and they could retrofit cellulose insulation after. I don’t believe there’s currently any insulation inside my ceiling. Do you think if I go this route that it will help reduce the level of airborne noise in a significant way in terms of noise from the TV and the noise from people talking? Thanks for your help.
Someone else online had mentioned that I could also maybe have them spray the insulation in first and then hire an electrician to install IC rated recessed lights so that the new lights wouldn’t be a fire hazard, but this way seems less soundproof than the first.
Hi Paul,
Sorry about your recessed lighting – we all have to learn things the hard way sometimes! Matt will be responding to your questions directly in an email – thanks for reading and good luck!
Hi.
my Father-in-law is looking to reduce the sound for a pump in a room next to his apartment. It’s a sheetrock wall. He has access to the room with the pump and permission to attempt something. It’s a larger pump, I haven’t seen it yet, but He seems to think a 3’x3′ box 2′ long would cover it up. The pump sounds through his entire apartment as a medium-loud thump…thump…thump..
I was going to build a box filled with acoustic foam to go around it and see up the ends as I was able, but after reading your blog entries, I’m wondering if you might have a more effective suggestion?
I would appreciate any advice.
Thank you,
db
Hi db,
Matt actually wrote another article about building soundproof enclosures for equipment like this: Soundproofing Small Loud Widgets
But another solution that may solve your problem is putting the pump on isolation mounts. If it is very low frequency noise and vibration, isolating the pump from other structures in the apartment may solve your issue enough to not have to ‘soundproof’ anything. You can see these mounts here: Isolation Mounts
You can also add Green Glue and an additional layer of drywall to the shared wall, or go an extra step and isolate it with isolation clips – or combine these two methods for the best results.
Please call in and speak with one of our Architectural Sales Reps – you can even ask for Matt specifically if you’d like: 800 782 5742
I need help to soundproof my bedroom. It is in a trailer. I already added another layer of drywall with green glue as well as putting tempered glass in front of the windows. Neither has worked. I also use a loud fan which doesn’t drain out the lowest noises. I am out in the country and I can hear sound for miles (literally). The biggest problem is bass that comes from moving and nonmoving sources as well as train and traffic noise. Moving is not an option and I don’t have alot of money to spend. Please help.
Hi TM,
Unfortunately your trailer is probably as soundproof as it is going to get without you spending a small fortune to add more airtight mass. My only piece of advice is to carefully find where sound is leaking in the most and try to mitigate it at the source. This includes doors, windows, gaps, or cracks.
I have tenants above me that I can hear everything they say and every step they take. I previously took up the old ancient tile and screwed down the sheeting and put new carpet and pad. What can I do to fix this problem?
Robert, if you’ve just installed new flooring I assume you wouldn’t be very open to the idea of taking it up and installing an underlayment. If you are, and if the ‘sheeting’ wasn’t an acoustical underlayment with STC and IIC ratings comparable to our Iso-Step, then Iso-Step is a solution that could help. Another solution is to install Green Glue and an additional layer of drywall to your ceiling.
Hi, I live in NYC and had pressurized walls built to create 2 bedrooms. With new building codes, the walls cannot go up to the ceiling and there is 18″ left to fill. How can I get creative/cost efficient to fill the top? I don’t think dry wall is an option. We are trying to create as much privacy/soundproof as possible for good $
Thanks
Dylan,
Hi there, pressurized walls are by definition very light, which is the exact opposite of what you want to block noise. Open areas also are a large path for sound to go through. The only real solution here is to add mass to the wall and have it be completed to the ceiling.
I rent an apartment and my neighbors are complaining about my television. How can I fix this without permanently altering the apartment?
Hi Steve,
This article may be helpful to you: Soundproofing an apartment
Please feel free to call in if you need more help: 800-782-5742
Hi Matt, I was reading your blog posts on soundproofing. People were telling me to use foam panels or egg cartons, I instinctively thought it would be a futile attempt and you confirmed it. I need to do something about my bedroom walls but this is a rented apartment so I can’t do anything destructive, not even sticking things on the wall. I could try hanging things on the wall from the exposed wooden beams in the ceiling but even with the ladder it’s still too high for me. I’m probably going to just fall from the weight of whatever I’m going to hang before I get it hung.
I hear my neighbours next door and I think it’s their toilet right beside my room. I hear everything. There’s a small closet high up in the wall that’s empty and the bottom seemed to be closed up using packed paper boxes. I hear impact noises too, aside from the nose-blowing, talking and peeing. I think they were slamming the doors of the closets placed against the wall and I hear them stomping up and down the stairs. I think the stairs are also against my wall.
Do you think it could help to hang a couple of heavy blankets on the walls (on most parts, the ceiling is slanted, don’t have anyone above me) or can i use a sound blanket or barrier? I can’t drill holes in the walls though to mount them. I obviously would have to fill up that abandoned closet up in the wall. Or do I have to build an enclosure around my bed? Thanks.
Do I have to cover the entire wall till it touches the ceiling or is ok if it’s a couple of feet from the ceiling?
Hi,
Wonder if i could get some advise on blocking bass sound.
Im building my house from scratch and for my aV room (17 ft by 24 ft) i intend to put 2 layers of concrete on all walls and ceiling. Underneath the floor is soil.
1. Would two 6 inch grade 30 concrete walls sandwiching 6 inch of air gap be sufficient to block low bass from leaking out? Assumming im putting in 2 solid core doors with an air gap of 6 inches as well.
2. Would filling the 6 inch gap be better or leaving the air in the gap better?
Thx in advance
CK Tan
Hi, I have a basement with exposed floor joists and I want to add something between the rafters that will at least help dampen the sound from the wood floor above. I know what ever I do won’t work really well because the sound will vibrate through the rafters, however do you have any advice for putting something in between the rafters to dampen the sound?
Thanks!