We would like to insulate under the floor in our master bedroom as it is directly above the living area of our 'granny flat'. Some kind of loose fill would be preferable as we do not want to take the whole floor up. Any suggestions?
Sound Insulation
- Thread starter Moira
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What do you intent to install on the floor (carpet, wood) or is that not on the list (yet)?
Otherwise you could included some proper sound-insulation underlayment and don't have to 'touch'/lift up the existing floor
Otherwise you could included some proper sound-insulation underlayment and don't have to 'touch'/lift up the existing floor
And it's not cheap 
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Moira:
Actually, the way sound moves through walls is basically the same as it moves through floors and ceilings, and understanding how that happens also explains why putting any sort of noise absorbant material BETWEEN the floor joists is not likely to do much good at all.
In a nutshell, the way a sound wave travels through a wall is astonishingly simple:
The sound wave hits the wall and makes it move. The movement of the wall reproduces another sound wave on the other side of it. Ditto for floors and cielings.
And, that extremely simple mechanism by which sound propogates through walls, floors and ceilings of a building is what gives rise to something called "The Mass Law" of noise transmission, which says:
A) That for every doubling of the mass of the wall (per square foot), the amplitude of that reproduced sound wave on the other side of the wall is reduced by 6 decibels, or 1/4 of it's previous value (cuz decibels are a logarithmic measurement).
B) That for every doubling of the frequency of the sound wave hitting the wall, the amplitude of that reproduced sound wave on the other side of the wall is reduced by 6 decibels, or 1/4 of it's previous value.
And, it's simple to understand why in terms of mass.
The heavier a wall is, the more inertia it has and the less it moves in response to an applied force. So, when a sound wave hits a heavier wall, that wall moves less and the amplitude of the sound wave the wall reproduces is less, so the noise on the other side of the wall is quieter.
Similarily, the heavier a wall is, the more inertia it has and the less quickly it can change it's direction of motion. So as the frequency of the sound wave hitting the wall increases, the more the inertia of the wall prevents it from moving in response to that sound wave.
And, now you know the reason why when someone in an apartment block is having a party at 3:00 in the morning, all the other tenants can hear a BOOM-BOOM-BOOM noise coming from that suite, but can't tell what song is playing. The reason is that the inertia of the walls, floors and ceilings effectively prevent the mid-range and high frequency sound waves from propogating through the building, and all you're left with are the lowest frequencies getting through.
And, that is ALSO the reason why newer apartment buildings built with 3/8 inch plasterboard walls on metal studs have more noise complaints between tenants than old buildings with 3/4 inch thick plaster on 2X4 fir studs. It's the inertia of those plaster walls and ceilings that kept homes and apartments quiet in the past.
So, while there are underlayments you can buy to cushion foot falls on the floor, the real solution to stopping noise propogation from one floor to another is to make the floor/ceiling construction between them heavier. So, if you live in an apartment building with concrete floors, you will have little noise coming from the floor above or the floor below.
You can also install soft, sound absorbant materials in the lively room. Soft materials like carpets, draperies, upholstered furniture absorb sound waves so that the sound wave that reflects off a soft surface will be less intense than the one that hit it.
Also, because of the way sound propogates through walls, floors and ceilings, if you can somehow prevent the movement of one side of the wall in response to the impact of the sound wave from causing the opposite side of the wall to move, then you've got the problem solved too.
And, in fact, vibration isolation is very effective in reducing noise propogation through walls. Basically, the idea here is that you build two separate parallel walls so that the movement of one side of the wall doesn't necessarily result in the movement of the other side. Consequently, a sound wave hitting one of those two parallel walls won't result in the other wall reproducing that same sound wave. However, while this works well with walls, it's not a practical solution for floors and ceilings which require solid support against the force of gravity. One way of doing that, however, is through the use of two separate joist systems; one set of joists holding up the floor above, and a completely separate set of joists holding up the ceiling below. And, in fact, my building is built that way (with two completely separate sets of joists between each floor), but I still get complaints when one tenant plays his stereo too loud. But, the complaining tenant is not complaining about the sound level. He's complaining that the low frequency BOOM-BOOM-BOOM vibrations he hears are annoying.
Hang on, lemme get you some web sites that'll explain more about noise transmission through buildings...
Actually, the way sound moves through walls is basically the same as it moves through floors and ceilings, and understanding how that happens also explains why putting any sort of noise absorbant material BETWEEN the floor joists is not likely to do much good at all.
In a nutshell, the way a sound wave travels through a wall is astonishingly simple:
The sound wave hits the wall and makes it move. The movement of the wall reproduces another sound wave on the other side of it. Ditto for floors and cielings.
And, that extremely simple mechanism by which sound propogates through walls, floors and ceilings of a building is what gives rise to something called "The Mass Law" of noise transmission, which says:
A) That for every doubling of the mass of the wall (per square foot), the amplitude of that reproduced sound wave on the other side of the wall is reduced by 6 decibels, or 1/4 of it's previous value (cuz decibels are a logarithmic measurement).
B) That for every doubling of the frequency of the sound wave hitting the wall, the amplitude of that reproduced sound wave on the other side of the wall is reduced by 6 decibels, or 1/4 of it's previous value.
And, it's simple to understand why in terms of mass.
The heavier a wall is, the more inertia it has and the less it moves in response to an applied force. So, when a sound wave hits a heavier wall, that wall moves less and the amplitude of the sound wave the wall reproduces is less, so the noise on the other side of the wall is quieter.
Similarily, the heavier a wall is, the more inertia it has and the less quickly it can change it's direction of motion. So as the frequency of the sound wave hitting the wall increases, the more the inertia of the wall prevents it from moving in response to that sound wave.
And, now you know the reason why when someone in an apartment block is having a party at 3:00 in the morning, all the other tenants can hear a BOOM-BOOM-BOOM noise coming from that suite, but can't tell what song is playing. The reason is that the inertia of the walls, floors and ceilings effectively prevent the mid-range and high frequency sound waves from propogating through the building, and all you're left with are the lowest frequencies getting through.
And, that is ALSO the reason why newer apartment buildings built with 3/8 inch plasterboard walls on metal studs have more noise complaints between tenants than old buildings with 3/4 inch thick plaster on 2X4 fir studs. It's the inertia of those plaster walls and ceilings that kept homes and apartments quiet in the past.
So, while there are underlayments you can buy to cushion foot falls on the floor, the real solution to stopping noise propogation from one floor to another is to make the floor/ceiling construction between them heavier. So, if you live in an apartment building with concrete floors, you will have little noise coming from the floor above or the floor below.
You can also install soft, sound absorbant materials in the lively room. Soft materials like carpets, draperies, upholstered furniture absorb sound waves so that the sound wave that reflects off a soft surface will be less intense than the one that hit it.
Also, because of the way sound propogates through walls, floors and ceilings, if you can somehow prevent the movement of one side of the wall in response to the impact of the sound wave from causing the opposite side of the wall to move, then you've got the problem solved too.
And, in fact, vibration isolation is very effective in reducing noise propogation through walls. Basically, the idea here is that you build two separate parallel walls so that the movement of one side of the wall doesn't necessarily result in the movement of the other side. Consequently, a sound wave hitting one of those two parallel walls won't result in the other wall reproducing that same sound wave. However, while this works well with walls, it's not a practical solution for floors and ceilings which require solid support against the force of gravity. One way of doing that, however, is through the use of two separate joist systems; one set of joists holding up the floor above, and a completely separate set of joists holding up the ceiling below. And, in fact, my building is built that way (with two completely separate sets of joists between each floor), but I still get complaints when one tenant plays his stereo too loud. But, the complaining tenant is not complaining about the sound level. He's complaining that the low frequency BOOM-BOOM-BOOM vibrations he hears are annoying.
Hang on, lemme get you some web sites that'll explain more about noise transmission through buildings...
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Here's an excellent web site from a group sponsored by the Canadian National Research Council that explains the technical nitty gritty of how noise propogates through walls and doors and windows:
http://131.251.21.249/local/acoustic/SoundTransmission.htm
And, here's a UK web site that seems to have ripped off a lot of the images that were on that NRC web site, but we let them do it.
http://www.customaudiodesigns.co.uk/help.htm
Anyhow, I forgot to explain why filling the space between the floor joists with sound absorbing material won't make a difference.
It's cuz when the sound wave from downstairs hits the ceiling drywall, that force will cause the joists to move. The movement of the joists will cause the floor above to move, and the movement of the floor is what reproduces the noise you hear that originates downstairs.
Filling the space between the floor joists with a sound absorbant material will help only to the extent that:
a) It'll increase the mass of the floor slightly, and
b) it'll reduce the vibrations of the drywall between the joists as a result of the sound wave hitting the ceiling.
But, the lion's share of the noise you hear from downstairs is still due to the movement of the floor as a whole as a result of the plasterboard ceiling below being hit by a sound wave.
Hope this helps explain noise to you.
http://131.251.21.249/local/acoustic/SoundTransmission.htm
And, here's a UK web site that seems to have ripped off a lot of the images that were on that NRC web site, but we let them do it.
http://www.customaudiodesigns.co.uk/help.htm
Anyhow, I forgot to explain why filling the space between the floor joists with sound absorbing material won't make a difference.
It's cuz when the sound wave from downstairs hits the ceiling drywall, that force will cause the joists to move. The movement of the joists will cause the floor above to move, and the movement of the floor is what reproduces the noise you hear that originates downstairs.
Filling the space between the floor joists with a sound absorbant material will help only to the extent that:
a) It'll increase the mass of the floor slightly, and
b) it'll reduce the vibrations of the drywall between the joists as a result of the sound wave hitting the ceiling.
But, the lion's share of the noise you hear from downstairs is still due to the movement of the floor as a whole as a result of the plasterboard ceiling below being hit by a sound wave.
Hope this helps explain noise to you.
Sure, that's why we always adive to make sure the floor doesn't touch any walls, doorposts or other sound-transporting structures.
Also, when installing a wooden floor using the floating method instead of nailing down or glueing down complete, noise reduction using underlayment will be better
Plus, Nestor, most posters here are DIY-ers, not builders/contractors/architects/interior designers. Basic instructions go a very far way in helping everyone, lectures (how true and/or well ment) tend to be OTT
Also, when installing a wooden floor using the floating method instead of nailing down or glueing down complete, noise reduction using underlayment will be better
Plus, Nestor, most posters here are DIY-ers, not builders/contractors/architects/interior designers. Basic instructions go a very far way in helping everyone, lectures (how true and/or well ment) tend to be OTT
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You can see how a guy like me doesn't know what side of the street to stand on...
WouldYouLike says "Plus, Nestor, most posters here are DIY-ers, not builders/contractors/architects/interior designers. Basic instructions go a very far way in helping everyone, lectures (how true and/or well ment) tend to be Over The Top."
Deluks says "Nestor, superb post there mate, considering the complexities of soundproofing that is one of the most easy to understand straightforward explanations of the process."
I was born confused, and this isn't helping.
WouldYouLike says "Plus, Nestor, most posters here are DIY-ers, not builders/contractors/architects/interior designers. Basic instructions go a very far way in helping everyone, lectures (how true and/or well ment) tend to be Over The Top."
Deluks says "Nestor, superb post there mate, considering the complexities of soundproofing that is one of the most easy to understand straightforward explanations of the process."
I was born confused, and this isn't helping.
Nestor_Kelebay said:You can see how a guy like me doesn't know what side of the street to stand on...
WouldYouLike says "Plus, Nestor, most posters here are DIY-ers, not builders/contractors/architects/interior designers. Basic instructions go a very far way in helping everyone, lectures (how true and/or well ment) tend to be Over The Top."
Deluks says "Nestor, superb post there mate, considering the complexities of soundproofing that is one of the most easy to understand straightforward explanations of the process."
I was born confused, and this isn't helping.
Sorry, my fault. It is easy to understand and straightforward for me to understand, but then I have a super-genius brain
JohnD said:
I'm all for that. sorry Nestor, didn't mean to confuse you, was just my 2p (I like straight forward advice I can use instantly, not a very long story on how or what and why, if you get my drift, but it's known I'm very impatient sometimes
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No problem, WouldYouLike. As I've said in other posts, I write my posts presuming that other people will also be reading them, and knowing how noise propogates through a building helps people understand what will and won't be effective in stopping noise from going from room to room or floor to floor.
But, I presumed that the problem the original poster was trying to address was the problem of noise from the living room being heard in the bedroom. If the problem is that of a squeeking bed being heard in the living room, the most effective solution in my estimation would be to take the bed frame apart and both tighten and lubricate any joints in it where one part of the bed frame can rub on another part of the bed frame.
When a floor squeeks when you walk over it, what's actually happening is that the wood floor boards (or subfloor) is actually rubbing on the nails which hold it down to the floor joists. That rubbing causes both the wood floor boards (or wooden subfloor) and the nail to vibrate as they rub against each other, and it's those vibrations that you hear as a high pitched squeeking noise. (just like the squeek you hear when the brake pads on your car vibrate as they rub against the brake rotor).
To fix a squeeky bed, you need to stop the bed frame from vibrating, and that's best done by lubricating any places where the parts of the bed frame rub against one another to convert those spots from a rubbing contact to a sliding contact. If no rubbing, then no vibrating and so, no squeeking noise.
But, I presumed that the problem the original poster was trying to address was the problem of noise from the living room being heard in the bedroom. If the problem is that of a squeeking bed being heard in the living room, the most effective solution in my estimation would be to take the bed frame apart and both tighten and lubricate any joints in it where one part of the bed frame can rub on another part of the bed frame.
When a floor squeeks when you walk over it, what's actually happening is that the wood floor boards (or subfloor) is actually rubbing on the nails which hold it down to the floor joists. That rubbing causes both the wood floor boards (or wooden subfloor) and the nail to vibrate as they rub against each other, and it's those vibrations that you hear as a high pitched squeeking noise. (just like the squeek you hear when the brake pads on your car vibrate as they rub against the brake rotor).
To fix a squeeky bed, you need to stop the bed frame from vibrating, and that's best done by lubricating any places where the parts of the bed frame rub against one another to convert those spots from a rubbing contact to a sliding contact. If no rubbing, then no vibrating and so, no squeeking noise.
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