Building a room within a room on a floating floor solutions

chag0101

Member
Joined
Dec 26, 2020
Location
MA
Hello! I have an impact noise attenuation question.

If I build a room within a room on a floating floor using a Mason spring jack type system, will this make low frequency impact noise coming from an upstairs neighbor practically inaudible at night (assuming it’s done properly)? I live in a high-rise (an upper floor) cast concrete apartment building with 8-inch(20cm) slabs and I am concerned about noise coming from dragging the furniture on tiles and laminate floor at night coming from an inconsiderate neighbor (I don’t have access to the noise source to treat it there).

It’s our bedroom where we sleep, 170 sq.ft (16 sq.m), square room with a 11ft ceiling (3.30m). The perimeter walls are built from 4in (10cm) concrete blocks. I plan to build internal walls from brick (for greater mass) resting on a Mason jacked up internal floor, the internal ceiling will be half as thick as the building slab (shall do 4in (10cm) max) resting on internal brick walls (no contact with outer walls) and will use rockwool (the type that won't saddle) to fill the 2in (5cm) cavity in between the walls and also between the ceiling and the outer slab (there I can do a 4in (10cm) gap or more if need be). Don't plan to use plaster boards. As mentioned, the floor will be Mason jack up type raised from the floor slab (leaving about 1in (2.5cm) cavity, not filled). I also plan to put a pair of insulated room entrance doors and double windows as well, mounted on silicone, no foam.

So, if I build a “room within a room” on a floating floor (completely decoupled on springs), even IF some noise still passes through, will it be perceived as airborne noise rather than structural noise if completely decoupled?

I can sleep through street noise, police sirens etc, no problem, but impact noise is a killer, you can hear it in your ear through a pillow boom, boom... (I think dominant frequencies are 30-50 hz and below). Hence, I am looking for complete de-coupling solutions.

My neighbors stay up all night every night and I have no other choice (other than selling) unless I can attenuate this noise somehow, or at least convert it to airborne noise.

Worth trying?

Thanks!
 

kmetal

Kyle P. Gushue
Well-Known Member
Joined
Jul 21, 2009
Location
Boston, Massachusetts
This can work. The design of it is not Diy, and its an expensive proposition.

The floating slab would need to be an octave below the lowest frequency you wish to isolate. Ideally it would be around 8hz to be tuned below the audible spectrum.

An all concrete assembly will have quite high TL values, which is good.

Considering its just human noise, not a bowling alley or drumkit, ect above, you may be able to get by with a more modest/cheaper assembly. A floating slab with timber frame walls/ceiling would likely do the trick.

You may also find that a simple floating floor made of rigid fiberglass, with 2x layers of plywood is a suitable alternative to floating slab on springs. You could then float the walls/ceiling, for a fully floated assembly.

The first thing you should do is test the conditions with an spl meter and RTA. This will tell you the SPL and Frequncy content of the noise. You have to work with accurate numbers, of the noise level when loud, and noise level when quiet. a basic spl meter and free REW software will be good enough for your needs. Otherwise an app on your phone will be useful, but less precise. You will need reliable test data before planning can go very far.

There are also vibration readout apps which you can rest your phone on the floor/wall/ceiling and it will tell you the frequncy of the vibration.

http://vibrationisolatorpro.com/

The assembly is strong as its weakest link, so having walls and ceiling that outperform your doors and windows incurs significant diminishing returns. You may find designing the TL to the achievable level of the doors and windows much more cost effective.

With impact noise its the decoupling that's significant, so the incredible mass of inner concrete walls and ceiling may not be needed.

If your in the US i highly recommend you contact Rod Gervias, who has masters level experience in studio design and high rise construction. If you don't have build it like the pro's, you will need it, as its a great resource for isolation construction.

These links to the PDFs will help show you TL of various assemblies.

The IR-586 shows acoustic tests of concrete block walls.

https://www.google.com/url?sa=t&sou...FjADegQIBhAB&usg=AOvVaw2sWjKP7MFPb9s2_gPSA_YN

IR-761 shows framed wall assemblies

https://www.google.com/url?sa=t&sou...FjAAegQIAhAB&usg=AOvVaw1Fwk6YyStmgaqR5TL3p9Ux

IR-811 shows floor assemblies which can help you estimate your roof.

https://www.google.com/url?sa=t&sou...FjAAegQIBRAB&usg=AOvVaw1X3r1nOAos9NspjzpXzPq0

BRN-217 shows test data concrete block with various finishes, including paint.

https://nrc-publications.canada.ca/eng/view/ft/?id=6d6d24d1-ad8a-4d3f-8eab-921245ca6efe
 

kmetal

Kyle P. Gushue
Well-Known Member
Joined
Jul 21, 2009
Location
Boston, Massachusetts
Do to the expenses and safety/code considerations, this isn't something to do unless absolutely sure it will meet your needs. It requires professional design and engineering. This is too much to be handled via forums. Tho we can help educate you and narrow things down, this is ultimately a professional job, for someone with plenty of experience in this specific construction method.

It is not difficult to short circuit a floating assembly by miscalculation of the loading, the load distribution on the assembly, and shoddy construction workmanship.

Another option would be to discuss with your neighbors about having a floating floor installed on their floor above your bedroom, which would be far cheaper, faster, easier, and stop the problem at the root.
 

chag0101

Member
Joined
Dec 26, 2020
Location
MA
The floating slab would need to be an octave below the lowest frequency you wish to isolate. Ideally it would be around 8hz... With impact noise its the decoupling that's significant, so the incredible mass of inner concrete walls and ceiling may not be needed… You may also find that a simple floating floor made of rigid fiberglass, with 2x layers of plywood is a suitable alternative to floating slab on springs.

Thank you so much for helping educate me on the subject and sharing the informative sources! I noticed how Canadian NRC has test results (concrete) for frequencies starting 60hz and higher…

I just have a couple of quick (clarifying) questions and would appreciate your reply.

1. Does this mean when you fully decouple, the inner structure’s mass needn’t surpass the weight of the outer structure to achieve a sound-wave frequency reduction to an octave below (ideally to around 8 hz)? Because obviously I cannot surpass the weight of the existing load bearing structure when designing an inner room…

2. I personally have the greatest confidence in full decoupling when it comes to isolating low frequencies, but I can be wrong as I am no expert. I’ve read some specs on fiberglass and learned that they are effective above 150hz (which I can suppress, cheaply, by wearing earplugs) the same goes for in combination with plasterboard. Besides, fiberglass will ensure full contact between the inner floor and building slab. So my question is, in case I have some difficulty procuring Mason type jack up springs (I am currently not in the US), can I *safely use* 1in rigid fiberglass (2x layers for overlapping seams) topping with 2x layers of plywood or concrete screed (2in) instead for my goals (noise from using furniture, footfall, potentially pets etc, i.e. normal household noise but at night)?

And finally, even if some low frequency sound still passes through after all the treatment (which I kinda feel it will), will it be perceived as a lighter version (like airborne noise) instead of Boom..boom which you can FEEL not just hear? So unsettling…

Btw, http://vibrationisolatorpro.com/ was also nice.

Many thanks for your efforts, and I am looking forward to hearing from you :)
 

kmetal

Kyle P. Gushue
Well-Known Member
Joined
Jul 21, 2009
Location
Boston, Massachusetts
1. Does this mean when you fully decouple, the inner structure’s mass needn’t surpass the weight of the outer structure to achieve a sound-wave frequency reduction to an octave below (ideally to around 8 hz)? Because obviously I cannot surpass the weight of the existing load bearing structure when designing an inner room…

It means you need to have the weight distribution of the floating slab calculated. Walls on the perimeter with a ceiling resting on them impart a different load on the slab than a bed and nightstand. The location of each object in the room must be pre determined.

The jacks, need to be calculated so there is adequate spring action. To much or too little weight will short circuit them. Think of a car's suspension system.

2. I personally have the greatest confidence in full decoupling when it comes to isolating low frequencies, but I can be wrong as I am no expert. I’ve read some specs on fiberglass and learned that they are effective above 150hz (which I can suppress, cheaply, by wearing earplugs) the same goes for in combination with plasterboard. Besides, fiberglass will ensure full contact between the inner floor and building slab. So my question is, in case I have some difficulty procuring Mason type jack up springs (I am currently not in the US), can I *safely use* 1in rigid fiberglass (2x layers for overlapping seams) topping with 2x layers of plywood or concrete screed (2in) instead for my goals (noise from using furniture, footfall, potentially pets etc, i.e. normal household noise but at night)?

I do not have test data for it, but Rod Gervias outlines the rigid fiberglass method in his book. Its reccomend used is for impact noise reduction on elevated decks.

It could work in conjunction with floated walls.

Since your case isn't exactly the case he describes in build it like the pro's, you would need to consult an acoustic professional to verify.

Rigid fiberglass is a pretty effective dampening material and doesn't readily transmit vibration. To what extent its effective i cannot say without data.

And finally, even if some low frequency sound still passes through after all the treatment (which I kinda feel it will), will it be perceived as a lighter version (like airborne noise) instead of Boom..boom which you can FEEL not just hear? So unsettling…

Tough to say for sure. If your fully decoupled then yes, it will be airborne.

Its certainly possible to eliminate both. Even drum kits can be tolerable with moderate room in room methods.

You need to test so you know how much TL you need from an assembly. Then its just matching your needs to a tested assembly and/or a bit of calculation.

Concrete is a good isolator so your starting from a good place.
 

chag0101

Member
Joined
Dec 26, 2020
Location
MA
I have a small place in a high-end high-rise bldg which has good enough airborne sound insulation but little if any impact sound insulation. The partition walls between adjacent apartments are double concrete walls (each 4in), the 2in cavity in between is filled with rigid fiberglass. When the side neighbor has high volume on his TV or plays music loud (no subwoofer) I can still hear some noise (though muffled) in the adjacent room and certainly less in other rooms. This noise is completely bearable and does not interfere with your sleep. But this makes me think the FLOOR is the ultimate culprit (flanking channel? Indirect pathways).

Now the floor which is an 8in concrete slab is covered with 2 inch sand and then 2in screed is poured on top of it. So, technically, there is no direct contact between the slab and screed, but the screed surface does touch all the walls and the walls rest on the slab (not on the screed). Hence sound travels through the floor.

Now, when another (upstairs) neighbor who is TWO floors up plays with his dog with toys (ball?) in the wee hours, I can hear that! Imagine how much air gap is between us (the whole one level) and I can still hear (feel) the impact sound. Granted some sound will travel via stiff beams, columns and diaphragms, but I think it is regular, lighter walls that transmit most of the noise. That’s why I think doing a good job at insulating the floor is the most important aspect of this task.

I’ve searched all over the Internet and wasn’t able to find a concrete floor solution floated on rigid fiberglass. Even when used underneath the plywood, the fiberglass, according to test results, provide a dampening effect at 150 hz and above; never seen fiberglass tested at 50 hz and below in any installation including in plasterboard structures (for walls for airborne noise) and in combination with plywood for floors. (Is there any?). That’s why I feel insecure about floating the concrete floor on fiberglass which as mentioned is also in full contact with the underlying slab (unlike jack up springs).

It means you need to have the weight distribution of the floating slab calculated. Walls on the perimeter with a ceiling resting on them impart a different load on the slab than a bed and nightstand. The location of each object in the room must be pre determined.

The jacks, need to be calculated so there is adequate spring action. To much or too little weight will short circuit them. Think of a car's suspension system.

But now based on your feedback, it appears using those springs is rocket science; I thought I would provide my inner cube dimensions and the overall weight, furniture included and could select an adequate spring with needed levels of deflection. I learned using springs can be tricky, I’ve seen some complaints on this forum from ten years ago that their usage fell short of expectations for HVAC installations by professionals (Rod Gervais was replying in the thread).

I was awakened three times last night, my lucky days are the ones when the upstairs neighbor is gone, I need to find some solution pretty soon or sell and move.

Is there any reasonable alternative to springs as a foundation?
 

kmetal

Kyle P. Gushue
Well-Known Member
Joined
Jul 21, 2009
Location
Boston, Massachusetts
The springs aren't rocket science, they just aren't DIY. It requires professional engineering, and proper building permits.

The fiberglass floating floor is a simple DIY, and not nearly as expensive as other methods. Like i said i haven't seen any test data for it, Rod would be the one to ask if its applicable to your case.

If the problem is in fact your floor, there are only the options to float a floor one way or another. Or float the neighbors floor.

If the problem is their floor/your ceiling, then there are more options.

To me it sounds like something isnt right. You have a lot of mass on your ceiling/neighbors floor, which would take alot of force to excite. That type of construction also has pretty low resonant frequency.

If you stomp your foot on a concrete floor, somone standing close by shouldn't even notice it.

Even with all the rigid connections between your rooms, it seems very atypical that a dog or human could cause that much disruption.

Perhaps you could try putting some properly sized/spec'd sorbothane pads under the feet of your bed, to try and decouple the bed from the floor. A fully isolated concrete room in room could easily cost as much as an apartment.

Again you have to test with the app and spl meter to define exactly what is going on. There is no general answer.
 

chag0101

Member
Joined
Dec 26, 2020
Location
MA
The springs aren't rocket science, they just aren't DIY. It requires professional engineering, and proper building permits.

The fiberglass floating floor is a simple DIY, and not nearly as expensive as other methods. Like i said i haven't seen any test data for it, Rod would be the one to ask if its applicable to your case.

If the problem is in fact your floor, there are only the options to float a floor one way or another. Or float the neighbors floor.

If the problem is their floor/your ceiling, then there are more options.

To me it sounds like something isnt right. You have a lot of mass on your ceiling/neighbors floor, which would take alot of force to excite. That type of construction also has pretty low resonant frequency.

If you stomp your foot on a concrete floor, somone standing close by shouldn't even notice it.

Even with all the rigid connections between your rooms, it seems very atypical that a dog or human could cause that much disruption.

Perhaps you could try putting some properly sized/spec'd sorbothane pads under the feet of your bed, to try and decouple the bed from the floor. A fully isolated concrete room in room could easily cost as much as an apartment.

Again you have to test with the app and spl meter to define exactly what is going on. There is no general answer.

Saw you on the other forum

The floor is part of it. I just stressed its importance in the context of the floated inner cube remodeling. As things are now, I can hear it most directly through my ceiling. No, I cannot hear normal footfall noise. If your run and vibrate the structure, then sure, a large dog could easily do that. But I can clearly hear heavy wooden chairs being displaced, its leg acts like a hummer, as if they were lightly tapping a hammer (or its wooden handle) on the floor. I’ve done some basic tests with iphone applications including the one you shared (thanks again). The dominant frequencies I encounter seem to be in the range of 20-50hz, and sound pressure peaks at 80db.

Do you think I can use a professional subwoofer as a white noise machine to mask the sudden onset of impact sound (furniture) in complete silence at night? Its brief but all it takes is one boom to wake you up. (A regular WN machine doesnt have low enough frequency to mask, and yes I tried to decouple my bedframe with thick rubber pads, they didn't help... perhaps the sound coming from the concrete structure is overpowering, that's why I am now thinking perhaps a subwoofer could help..).
===

An acoustics guy confirmed that I could try a sub for masking... What spec should I pay attention to when selecting for my particular needs (using as a white noise machine, 7hours a night) other than the lowest hz (down to 20?)? Since I don't know much, I would go like if its heavy, its good, as long as its ok hz wise. Any recommended models under $3K? (the cheaper, the better). Thanks!

To purchase at my own risk. If it doesn’t work its ok. Pls recommend brands or give me some hints (specs).


Do you think Yamaha NS-SW300 Subwoofer will work?

its only $500 but it says 20hz, Weight 39.7 lbs

https://usa.yamaha.com/products/audio_visual/speaker_systems/ns-sw300/specs.html#product-tabs
SubwooferDriverOutput PowerFrequency ResponseAdvanced YSTHigh-Efficiency Power AmplifierTwisted Flare PortBASS (Bass Action Selector System)Auto StandbyStandby Power ConsumptionSystem ConnectorBass Action Selector SwitchPhase ControlAluminum Front PanelPower and Volume SwitchDimensions (W x H x D)Weight
NS-SW300
NS-SW300
Subwoofer
Driver 10” cone
Output Power 250 W
Frequency Response 20-160 Hz
Advanced YST Yes
High-Efficiency Power Amplifier Yes
Twisted Flare Port Yes
BASS (Bass Action Selector System) Yes
Auto Standby Yes
Standby Power Consumption 0.3 W
System Connector Yes
Bass Action Selector Switch Yes
Phase Control Yes
Aluminum Front Panel No
Power and Volume Switch Yes (front panel)
Dimensions (W x H x D) 13-3/4” x 14-3/8” x 16-1/2”
Weight 39.7 lbs.
 

chag0101

Member
Joined
Dec 26, 2020
Location
MA
My Yamaha sub (made in Indonesia) has arrived.

It has Frequency Response 20-160 Hz, and its adjustable crossover has 40-140hz range. I connected through normal L/R mode and measured its frequency. It goes to 24hz @256 FFT 1/3 octave.

I also played Frequency Sweep 1-100hz (Bass Test) 1080p HD
and its immediately responsive. So I can assume it does have close to 20hz.

I am now playing digital recording (brown noise) continuously (it just rattles nothing else is audible). I am using maybe 3% volume, the floor vibrates, and I have 60db in the room, bass 0.02, power intensity 2.15. Is it ok to run it like that continuously for 8 hours--it wont break down easily?
 

chag0101

Member
Joined
Dec 26, 2020
Location
MA
Happy New Year already!

And thanks much for your inputs.

The sub exceeded all my expectations. Yesterday, I was able to sleep for the first time in many many weeks. I set my sub at 60db playing looped digital brown noise. It produces high quality, soft bass which is nice. I put cotton swabs in my ears additionally to dampen mid-range frequencies (I didn’t use earplugs those are more aggressive). I was able to sleep through the whole night without interruption, and mind you, yesterday was particularly noisy. I did wake up once but only after about 6 hours of continued sleep and that wasn’t due to any external bang that I’ve always dreaded. I could tell that because I wasn’t alarmed when I woke up and could easily go back to sleep. So I will continue to test it but if today is any indication, it was a success.
 
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