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Protecting neighbor in apt with thin walls
Old 11th November 2009
  #1
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Protecting neighbor in apt with thin walls

Sorry - I'm sure that this must have been discussed at some point. I'm really very ignorant about acoustic treatments - I know nothing about this subject at all, and have never had to deal with it really.

While I play my electronic stuff at very reasonable volumes, the next door neighbor has complained, and while I feel pretty righteous about the volumes that I play at, at the same time I'd want to cause him as little annoyance as possible.

What could I put on the adjoining wall to block the transmission of sound, especially the bass register? I'm looking to get this done cheaply, and with a minimum of skill (I'm pretty inept when it comes to putting stuff together).

Hope that the question isn't too silly.

Thanks.
Old 11th November 2009
  #2
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you really cant do anything for bass. well, you could build another wall. A thick wall with a big air gap. Or just get monitors that represent the bass well but not exaggerate it like the Adams A7 or something. Then treat with rock wool or mineral wool bass traps. tons of threads about those around.
Old 11th November 2009
  #3
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Quote:
Originally Posted by Math5461 View Post
you really cant do anything for bass. well, you could build another wall. A thick wall with a big air gap. Or just get monitors that represent the bass well but not exaggerate it like the Adams A7 or something. Then treat with rock wool or mineral wool bass traps. tons of threads about those around.
I'm not going to be building another wall.

My monitors don't exaggerate the bass, and I very rarely even use bass per se at all. But that is apparently the effect of the sound coming through the wall.
Old 11th November 2009
  #4
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Quote:
What could I put on the adjoining wall to block the transmission of sound, especially the bass register? I'm looking to get this done cheaply, and with a minimum of skill (I'm pretty inept when it comes to putting stuff together).
Quote:
My monitors don't exaggerate the bass, and I very rarely even use bass per se at all. But that is apparently the effect of the sound coming through the wall.
There's nothing you can "put on" the wall to block low-frequency sound transmission, cheap or not. If your neighbor is hearing bass, you're "using" bass, whether you know it or not. If you're room isn't treated for bass, though, you could be sending oceans of it through to your neighbor without hearing it yourself. What's your acoustic treatment situation?
Old 11th November 2009
  #5
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Show some respect to your neighbour and buy some headphones. If he/she can hear it and is bothered by it, you are probably doing something wrong by producing that noise. Apartments are shared spaces with shared walls. Noise transmittance is unavoidable if you are making noise. Some apartments transfer more than others. If you are in a noisy one, cut your neighbors some slack and get some nice cups.

There is nothing more annoying in an apartment than having to listen to an incessant BOOM BOOM BOOM BOOM BOOM BOOM BOOM because someone in the building likes their europop and doesn't think it's too loud.
Old 11th November 2009
  #6
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Quote:
Originally Posted by Brainchild View Post
There's nothing you can "put on" the wall to block low-frequency sound transmission, cheap or not. If your neighbor is hearing bass, you're "using" bass, whether you know it or not. If you're room isn't treated for bass, though, you could be sending oceans of it through to your neighbor without hearing it yourself. What's your acoustic treatment situation?
I think that you understand what I'm saying. The sounds aren't bass heavy. So, if that is the effect in the next apt, then the higher frequencies are being filtered out.

I have no acoustic treatment per se. I play softly - no louder than normal tv or stereo apt volumes. Outside of my front apt door, the sound is not audible period.

The monitors are Adam p22A's - I don't think that they are hyping the bass, and I'm not boosting the bass in any other way.
Old 11th November 2009
  #7
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Quote:
Originally Posted by mobius.media View Post
Show some respect to your neighbour and buy some headphones. If he/she can hear it and is bothered by it, you are probably doing something wrong by producing that noise. Apartments are shared spaces with shared walls. Noise transmittance is unavoidable if you are making noise. Some apartments transfer more than others. If you are in a noisy one, cut your neighbors some slack and get some nice cups.

There is nothing more annoying in an apartment than having to listen to an incessant BOOM BOOM BOOM BOOM BOOM BOOM BOOM because someone in the building likes their europop and doesn't think it's too loud.
I have nice headphones. I have never been able to use them for hours at a time.

The manager of the apt used to live in the adjoining apt, and he didn't not think that the levels were excessive. He explained to this new neighbor what the situation was before he moved in. And I"m not talking about the so called quiet hours (between 10 pm and 8 am) - the volumes are even lower then.

I don't listen to europop, and it most definitely isn't too loud. If all I am going to get here is condescension, then there really is no need to post.
Old 11th November 2009
  #8
Short of going to headphones, the only other "best bet" is to contact your landlord and let them know that while you feels your neighbor's complaints aren't entirely justified, you want to bring the situation to their attention.

In that if you are listening to music at reasonable residential levels, the building is not constructed so as to minimize this issue.

While well made, upper end apartments are well made to isolate the neighbors from each other, the construction of your apartment may be sub standard from a couple of standpoints... to wit;

If you can hear each others conversations
If you have excessive heating and cooling bills
If you cannot listen to music at nominal levels (sub 72db)

I would suspect that there is little to no insulation in the stud cavities, nor is there likely a firewall between the units.

The property manager should be made aware that this is something that they really should advise the property owner about. e.g. local ordinances regarding firewalls and insulation and that the property owner may not have received, yet paid for... (IF this is a newer structure.)

Most states here, have minimum noise isolation codes, to ensure at least a reasonable amount of individual privacy. If your building falls under these ordinances, the property owner should ensure that the structure complies with these codes.

If it's an older building.... Say, 15 years or older, there prolly ain't squat you can do except wear cans...... or move.
Old 11th November 2009
  #9
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Quote:
Originally Posted by droolmaster0 View Post
I have nice headphones. I have never been able to use them for hours at a time.

The manager of the apt used to live in the adjoining apt, and he didn't not think that the levels were excessive. He explained to this new neighbor what the situation was before he moved in. And I"m not talking about the so called quiet hours (between 10 pm and 8 am) - the volumes are even lower then.

I don't listen to europop, and it most definitely isn't too loud. If all I am going to get here is condescension, then there really is no need to post.
I didn't mean to condescend. I was speaking from experience as someone who had to move from the last apartment he lived in (and will ever live in) due to constant, annoying music. The walls in a poorly constructed apartment can carry bass like crazy.
Old 11th November 2009
  #10
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Quote:
Originally Posted by mobius.media View Post
I didn't mean to condescend. I was speaking from experience as someone who had to move from the last apartment he lived in due to constant, annoying music. The walls in a poorly constructed apartment can carry bass like crazy.
Understood. But, from his note:
"Can you please use headphones after 7 pm weekdays and on weekends".

So, even after being warned by the apt manager, who used to live in that apt and knows about how loud things are - he chose to move in, and is now asking me NEVER to play music on speakers. I don't consider that to be reasonable. I'm certainly willing to try lowering the volume even further, and using headphones more of the time - but not exclusively.
Old 11th November 2009
  #11
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Hmm. If you don't have them, I would get some isolation pads (Mopads etc.) for your monitors to decouple them from your desk or floor, if you don't have them already. Sometimes a desk or floor can act as a resonator and pass vibrations on to a neighbor. Other than that though, like the others said, there aren't much in terms of sound treatment that will help with that particular problem.

You should write him a note to "please use earplugs after 7 pm." Seriously though, I try very hard not to be an annoying neighbor, but there needs to be reasonble compromise here. My advice would be to measure how loud you play your music with an spl meter, and then tell your neighbor that you ARE willing to change your habits for HIS benefit. Something like the following

1) You purchased isolation pads (be sure to convey the cost) to help with the situation
2) You will only listen to louder untill 7pm
3) After 7pm, you will turn it down to 72 db (or whatever you choose as tolerable), a reasonably quiet volume
4) After 8:30pm (or even 9), you will don headphones. Tell him you just bought some for him.

Inform your landlord of all your sacrifice and comprimising as well. Look at all the the stuff you're doing for your neighbor! What a great guy you are!
Old 11th November 2009
  #12
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Oh and the request for you to wear headphones after 7pm on weekends is absurd.
Old 11th November 2009
  #13
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Hrm, yeah this sounds more like a generally unpleasant living situation than a specifically studio-related problem. Unfortunately, it doesn't sound like there's any simple easy way out of it.
I think there was a pretty well-thought-out thread on here fairly recently in which someone recommended finding out the local noise ordinance sound level limits, getting an spl meter, and just making sure you stay below that level. In that way, at the very least you're in no legal danger from your neighbor. If they're expecting unreasonable concessions from you, you may just end up having to push back.
Old 11th November 2009
  #14
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If it were me I'd try and keep the neighbour onside, set the volume to what you think is a reasonable level and go round there and see what's actually making it through the wall, if it's hardly anything find out what the code is for your building and say that you won't violate those terms.

If he has a point start looking into what can actually be done, isolating monitors from mechanical vibrations (foam under speakers) a second wall wouldn't be too difficult, explain that music is a great passion of yours and you appreciate his situation so maybe he could split the cost with you?

But get a dialogue going, that would be my first step.

Hope that helps
Old 11th November 2009
  #15
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Quote:
Originally Posted by DerlinStiles View Post
Oh and the request for you to wear headphones after 7pm on weekends is absurd.
Actually, I believe that the request was for after 7 pm on weekdays, and ALL weekend. Otherwise he could have just said after 7 pm every day.....
Old 11th November 2009
  #16
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Quote:
Originally Posted by Brainchild View Post
Hrm, yeah this sounds more like a generally unpleasant living situation than a specifically studio-related problem. Unfortunately, it doesn't sound like there's any simple easy way out of it.
I think there was a pretty well-thought-out thread on here fairly recently in which someone recommended finding out the local noise ordinance sound level limits, getting an spl meter, and just making sure you stay below that level. In that way, at the very least you're in no legal danger from your neighbor. If they're expecting unreasonable concessions from you, you may just end up having to push back.
I'd be surprised if the music volume is above normal conversation levels. I'm going to pick up a cheap db meter just to make sure.
Old 11th November 2009
  #17
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the monitors are on stands on the opposite side of the room from the wall through which the sounds are being transmitted. It doesn't seem plausible to me that it's being transmitted through the floor, and then through the opposite wall, especially at the low volumes that they are being played at.

I'm going to pick up a db meter, but I think that it will prove that the volumes are VERY low.

And that's the thing - I'm always considerate of my neighbors - I consider myself to already be compromising. Not that I won't make even more of an effort. But we're not starting from a situation where I'm playing loud music at all.

Quote:
Originally Posted by DerlinStiles View Post
Hmm. If you don't have them, I would get some isolation pads (Mopads etc.) for your monitors to decouple them from your desk or floor, if you don't have them already. Sometimes a desk or floor can act as a resonator and pass vibrations on to a neighbor. Other than that though, like the others said, there aren't much in terms of sound treatment that will help with that particular problem.

You should write him a note to "please use earplugs after 7 pm." Seriously though, I try very hard not to be an annoying neighbor, but there needs to be reasonble compromise here. My advice would be to measure how loud you play your music with an spl meter, and then tell your neighbor that you ARE willing to change your habits for HIS benefit. Something like the following

1) You purchased isolation pads (be sure to convey the cost) to help with the situation
2) You will only listen to louder untill 7pm
3) After 7pm, you will turn it down to 72 db (or whatever you choose as tolerable), a reasonably quiet volume
4) After 8:30pm (or even 9), you will don headphones. Tell him you just bought some for him.

Inform your landlord of all your sacrifice and comprimising as well. Look at all the the stuff you're doing for your neighbor! What a great guy you are!
Old 11th November 2009
  #18
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I'm pretty lucky- my neighbors are cool. I live in a rowhouse. BOTH of my roomates are drummers and the rule is no drums after 9:30pm on weekdays Sometimes they ask if they can play later than that! Drummers have some nerve. Last week, one of them set up a kit in his room on the second floor, I said "nice try." tutt If we have a party on a weekend eve with live music, I make sure to invite all my neighbors (even though I know they'd never come in a million years). This technique works really well. I don't think I've ever had the po-po show up, not once. Being really nice, overly nice, to your neighbor might make him leave you alone. People are wierd- they can decide what bothers them and what doesn't.
Old 12th November 2009
  #19
Quote:
Originally Posted by droolmaster0 View Post
the monitors are on stands on the opposite side of the room from the wall through which the sounds are being transmitted. It doesn't seem plausible to me that it's being transmitted through the floor, and then through the opposite wall, especially at the low volumes that they are being played at.
Haven't you ever heard a car go by with all the thumpin' bass coming from the subs in the trunk, right through your closed windows and doors?

Those low frequencies WILL travel pretty long distances, even through very significant structures... even whale songs can travel for hundreds of miles in water. Granted water isn't quite the same as transferring energy from air to building materials, but you get the idea.

Flanking noise is one of the biggest challenges in getting isolation. e.g. The only way to NOT have flanking noise is to decouple, or isolate, one room from another.

This is the concept of what is called room within a room design.

A perfectly isolated room would be suspended, in free space, on all sides, top and bottom.

Any surface that this perfectly isolated room might touch, will most definitely transfer energy from one surface to another... and THAT is flanking noise.

It's all but impossible to stop it, but you can do a lot to maximize your isolation. Unfortunately, you're not going to be able to do any of that as it would essentially be a new building.

Your speakers are facing the direction that's the neighbor who's complaining... bonus. So, you're pushing the energy straight into the neighbor's wall.

I'm also willing to guess that either your room where you listen, and/or the neighbor's room is either square, or it's close to a 1:1, 2:1 or 3:1 ratio in at least 2 directions.

I suppose you could layer 2" 703 and alternating 3/4" plywood against your walls... but who wants to look at plywood all day? And even then, it won't stop the energy from flanking through the floor or the ceiling/roof.

You might try moving your monitors forward a coupla' inches at a time, and check with the neighbor to see if it's better or worse... You could be activating the lowest nodes in one or more rooms... and thus, everything that's centered on that f0, or a harmonic, could be pouring in the neighbor's place... and exactly why they created cross talk limits between apartments and condo's.
Old 12th November 2009
  #20
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Quote:
Originally Posted by xaMdaM View Post
Haven't you ever heard a car go by with all the thumpin' bass coming from the subs in the trunk, right through your closed windows and doors?

Those low frequencies WILL travel pretty long distances, even through very significant structures... even whale songs can travel for hundreds of miles in water. Granted water isn't quite the same as transferring energy from air to building materials, but you get the idea.
no - not trying to argue (clearly I'm not an expert in this), but I don't quite get it. When a car boom box sound comes into the room, it is doing so because it is travelling through the air, and then through the windows because the windows don't keep out the sound. It's not because the bass sounds are making the ground vibrate, the outside of the building vibrate, my window vibrate. The transmission is more direct. And the sounds are very loud....in the case of my speakers, the volumes are not loud, the speakers are on stands, and the implication seems to be that because they are not isolated enough (sorry if terminology is not correct) that the bass energy is transmitted through the floor, making the wall vibrate. Would this really happen at low volumes? I will verify tomorrow when my db meter arrives, but we're talking conversation volume, if that.

Quote:
Flanking noise is one of the biggest challenges in getting isolation. e.g. The only way to NOT have flanking noise is to decouple, or isolate, one room from another.

This is the concept of what is called room within a room design.

A perfectly isolated room would be suspended, in free space, on all sides, top and bottom.
Could I accomplish this with drugs?

Quote:
Any surface that this perfectly isolated room might touch, will most definitely transfer energy from one surface to another... and THAT is flanking noise.
but again, it doesn't make INTUITIVE sense (meaning that I might be wrong) that this would happen through speakers on stands, through the floor, through the wall, at low volumes.

Quote:
It's all but impossible to stop it, but you can do a lot to maximize your isolation. Unfortunately, you're not going to be able to do any of that as it would essentially be a new building.

Your speakers are facing the direction that's the neighbor who's complaining... bonus. So, you're pushing the energy straight into the neighbor's wall.

I'm also willing to guess that either your room where you listen, and/or the neighbor's room is either square, or it's close to a 1:1, 2:1 or 3:1 ratio in at least 2 directions.
I think that you mean that it's rectangular in shape - yes - looks like it's about 2/1.

Quote:
I suppose you could layer 2" 703 and alternating 3/4" plywood against your walls... but who wants to look at plywood all day? And even then, it won't stop the energy from flanking through the floor or the ceiling/roof.

You might try moving your monitors forward a coupla' inches at a time, and check with the neighbor to see if it's better or worse... You could be activating the lowest nodes in one or more rooms... and thus, everything that's centered on that f0, or a harmonic, could be pouring in the neighbor's place... and exactly why they created cross talk limits between apartments and condo's.
Well, again - I'm arguing somewhat intuitively, and therefore might be totally full of it - but I can see what you're saying at loud volumes, but not at conversational volumes.

I since have had a more in depth description from the apt manager, and I think I know what might actually be happening. The complaint is about 'repetitive bass patterns'. Now, I don't do 'bass' patterns per se, but generally what I'm working on is an analog modular system, and I'll usually start out by using an analog sequencer, generating a pretty basic pattern, before I devolve it into sonic nonsense. I think from my conversation with the manager, that the guy is trying to study, and he hears the sounds faintly, but they are repetitive, and driving him crazy. And, because they are at such low volumes, I will sometimes leave them playing while I cook dinner, or go into the next room, etc.

I think that paying more attention at this stage - making sure that the volumes are even lower at this point, or using headphones more often at this point, and turning the stuff off when I don't need it on, will probably make a big difference. But I had the apt manager in here while some stuff was playing, and he said that it wasn't a problem - so I think that it is more psychological than sonic - the guy is trying to study, and he here's this obnoxious analog sequenced pattern, and it repeats, and repeats and repeats.
Old 12th November 2009
  #21
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Well, time to invest in some good head phones. Good pair of cans are fun when in the creative mode then you can switch to those kick ass adams when your neighbors aren't home. Good luck because other that, as far as I can tell, your screwed. And I mean that with the utmost respect.
Old 12th November 2009
  #22
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Quote:
Originally Posted by Math5461 View Post
Well, time to invest in some good head phones. Good pair of cans are fun when in the creative mode then you can switch to those kick ass adams when your neighbors aren't home. Good luck because other that, as far as I can tell, your screwed. And I mean that with the utmost respect.
I have very good headphones (sennheiser hd-650). Drives me crazy to use them exclusively for long periods.

I don't know when he is home and when he isn't.

I don't see that I'm screwed at all. If my volume is at conversational level before 10 pm, I'm not really sure that he has much recourse. I, of course, will try to do whatever I can to cooperate with him, but I won't use headphones all weekend, and every evening (all of my free time).
Old 12th November 2009
  #23
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I've dealt with stuff like that before. Some people think they should have total silence. If someone needs total silence perhaps they shouldn't have moved into an apartment. Do your thing and don't worry about him.
Old 12th November 2009
  #24
There's little point in trying to explain the physics to you in a forum where it's improper to quote copyrighted material. I'm not a physicist or mathematician, so it's a bit tough for me to cleanly explain all this without posting protected publications.

I would suggest getting a copy of any number of books at your local university's library on the physics of music and studio construction, if you really want to understand the why's and how's of flanking, isolation and sound proofing. I would suggest Rod's Gervais' book; "Build It Like the Pro's", Alton Everest's book; "Master Handbook of Acoustics", Beranek's; "Physics of Music", and Philip Newell's; "Recording Studio Design".

Most of it IS counter intuitive in what you would think is a logical approach to understanding and dealing with the physics of sound... ESPECIALLY, low frequency energy.

I will leave this thread with one last attempt to clarify what you are dealing with... When you walk across a floor, knock on a door, open or shut a door to a room, drive a nail in a wall, play music or run water in a tub, you are generating sound energy. ANY and ALL of that energy gets radiated in the air AND into the physical structure. Period.

ANYTHING that is physically attached to that structure will transmit that energy from itself to that attached structure. (including the air column in that structure) This is simple wave propagation.

The amount of energy that is transferred is inversely proportional to the square of the distance, for any single given frequency. So, you would think that after a couple of feet, the energy will dissipate from absorption.

However, this is complicated by the fact that there are multiple paths for the energy to travel, even from a single source, and "musical" low frequency wavelengths can be as long as 64 feet (and longer) to complete an individual cycle. So for low frequencies, many physical "barriers" in a structure are just a hole for those frequencies to flow through.

It is further complicated by the fact that individual components in a structure have their own resonant frequencies... which may actually help or hurt the energy transfer of the wave propagation.

So, while you may not hear low frequencies in your room, someone 64 feet away may be hearing it in all it's glory. (boom box subs in a car driving down the street)

There are some things that are better left to the experts, and maybe this is one thread better left to Andre's and Rod's (and obviously some of the other folks here) expertise to try to explain to you.
Old 12th November 2009
  #25
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ok - so, you seem to be saying that there is every possibility that, even at low volumes, and the speakers on stands (on a rug), the low frequency energy is still being transmitted through the floor to the wall...

But cement blocks should help?

Quote:
Originally Posted by xaMdaM View Post
There's little point in trying to explain the physics to you in a forum where it's improper to quote copyrighted material. I'm not a physicist or mathematician, so it's a bit tough for me to cleanly explain all this without posting protected publications.

I would suggest getting a copy of any number of books at your local university's library on the physics of music and studio construction, if you really want to understand the why's and how's of flanking, isolation and sound proofing. I would suggest Rod's Gervais' book; "Build It Like the Pro's", Alton Everest's book; "Master Handbook of Acoustics", Beranek's; "Physics of Music", and Philip Newell's; "Recording Studio Design".

Most of it IS counter intuitive in what you would think is a logical approach to understanding and dealing with the physics of sound... ESPECIALLY, low frequency energy.

I will leave this thread with one last attempt to clarify what you are dealing with... When you walk across a floor, knock on a door, open or shut a door to a room, drive a nail in a wall, play music or run water in a tub, you are generating sound energy. ANY and ALL of that energy gets radiated in the air AND into the physical structure. Period.

ANYTHING that is physically attached to that structure will transmit that energy from itself to that attached structure. (including the air column in that structure) This is simple wave propagation.

The amount of energy that is transferred is inversely proportional to the square of the distance, for any single given frequency. So, you would think that after a couple of feet, the energy will dissipate from absorption.

However, this is complicated by the fact that there are multiple paths for the energy to travel, even from a single source, and "musical" low frequency wavelengths can be as long as 64 feet (and longer) to complete an individual cycle. So for low frequencies, many physical "barriers" in a structure are just a hole for those frequencies to flow through.

It is further complicated by the fact that individual components in a structure have their own resonant frequencies... which may actually help or hurt the energy transfer of the wave propagation.

So, while you may not hear low frequencies in your room, someone 64 feet away may be hearing it in all it's glory. (boom box subs in a car driving down the street)

There are some things that are better left to the experts, and maybe this is one thread better left to Andre's and Rod's (and obviously some of the other folks here) expertise to try to explain to you.
Old 13th November 2009
  #26
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droolmaster0, why don't you turn on your music and go over to your
neighbour's and hear what's coming through ? I think it would be good to
discuss the matter with your neighbour. They may have a point.

Paul P
Old 13th November 2009
  #27
Quote:
Originally Posted by droolmaster0 View Post
ok - so, you seem to be saying that there is every possibility that, even at low volumes, and the speakers on stands (on a rug), the low frequency energy is still being transmitted through the floor to the wall...

But cement blocks should help?
It's definitely possible that the energy is still transmitting, and cement blocks are not guaranteed to help. Solid elements like that actually often make pretty good transmitters when a vibration source is in contact. As you have observed already, there is both air borne and structure borne sound to consider. If you are convinced this is structure borne, then isolating the speakers from the structure is a good idea, though a more difficult one than you might expect.

Vibration isolation is unfortunately not a simple thing. Many think that some simple cones, foam, or rubber is all that's necessary. At best, these attempts are ineffective; at worst, they can actually amplify a vibrational problem and increase transmission.

The following is a quick primer on vibration isolation I wrote a couple years back. It is by no means a step-by-step guide to DIY vibro-iso, but rather an introduction to give you a feel for the elements involved, and perhaps a jumping-off point to investigate more effective isolation possibilities.

Begin quote:

Transmissibility is the ratio of the transmitted force to the driving force, where a 1 would represent all force transmitted into the structure, and 0 would be no sound transmitted (0.02 is about the real world limit). A resilient isolator's job is to reduce the transmitted force, but the wrong choice can actually resonate with the force, thereby increasing the transmitted force above 1. So a worst case scenario is not that the isolator will simply be ineffective, but that it will actually amplify the transmission.

The "driving" or "forcing" frequency (Ff) is the lowest frequency generated by the source. A piece of equipment with a fan rotating at 1650 RPM would have a Ff of 1650Γ·60 s/min=27.5 Hz. A subwoofer with a low frequency extension to 25 Hz is simply a Ff of 25 Hz.

The natural frequency is that which the resilient element tends to restore itself after displacement, or the spring-mass system will bounce if displaced from its resting place. Imagine the Jack-in-the-box bobbing up and down after it is opened. The rate of the bob is the natural frequency of the spring, or Fn.

The basic goal is to choose an isolator that, under load (with the equipment in place) will have a Fn of less than 1/10 the Ff. Again, it can get quite complex, but this starting point satisfies most simple applications.

Unfortunately, we are not done yet. we need to consider static deflection next. Static deflection is the distance in inches by which the resilient element (the isolator, whether various neoprene pads or pucks, spring mounts, or some other more esoteric materials) will compress under the load of the equipment. The proper static deflection can be calulated with the following simple equation:

S.D.=9.8/Fn^2

That is 9.8 divided by the natural frequency squared. You also want your desired static deflection to be in the middle of the range of your isolator. If you need 1/4" S.D., you don't want it to be 1/4" of a 4" spring. If you need 5/8" S.D, it'd best not to be a 3/4" pad. If it is compressed nearly all the way, or barely at all, it likely won't have the springiness and travel you are looking for. You also want an isolator that isn't damped very much. Things that don't spring back quickly, like carpet and foam, don't make very good low frequency isolators.

Steel springs, neoprene mounts, and neoprene pads are common choices. Springs offer S.D. of about 1/4" to 4" for Fn of 6.3 to 1.6 Hz. Mounts run from 1/10" to 1/2" S.D. for Fn of 10 to 4.4 Hz. Pads run 2/100" to 1/4" for Fn of 22 to 6.3 Hz.

Sometimes (often) you will see springs in line with neoprene isolators. These help to further isolate the equipment from vibrations travelling down the helix of the spring. You don't want too rigid a connection as it will prevent the bounce and offer a structure-bourne vibration path to the building. Low frequency energy, especially from speakers, will also radiate directly into a room, exciting surfaces and other objects in the room, so it is not appropriate on it's own for transmission loss into adjacent spaces, AKA soundproofing.

Here are some links to some sources of isolators or isolating materials:

Kinetics Noise Control, Room Acoustics, Vibration Isolation, Seismic Restraint
Shock and vibration solutions | Sorbothane
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