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For you acoustics pros and wizards.
What's the best way to decouple a component from vibrations in the bass region--say, below 200 Hz?
I live in a concrete and steel building where the building resonates at low frequencies. This is pretty common I think. I can hear every note of the bass line of the music played by my downstairs neighbor, but hardly anything else. And I don't like listening to her bass lines. Also, if coupling to the structure is this strong--if that much energy is passing into the building--it can't be good for the sound, right?
So I'd like to come up with an easy, cheap solution that I can use myself and offer to neighbors to solve this problem. Obviously, there will be some coupling through the air, and there's probably not much that can be done about that. But it shouldn't be that hard to put something under the speakers, or the TV, or whatever's making noise, that would keep it from coupling directly to the building's structure.
What's the best approach?
Thanks,
Jim
Follow Ups:
The (Air-Borne) music from your downstairs neighbour is being absorbed into the structure to become.......surprise, surprise......Structure-Borne sound. The Mid to High frequencies can be absorbed into heat by the concrete floor separating your apartments, but the large wavelength Lower frequencies will tend to pass through the concrete to be converted back to Air-Borne sound. I'm guessing that that there is no suspended plasterboard ceiling under the concrete slab?.......for if there is, it provides the cheapest and easiest cure to the problem. A double layer of plasterboard ceiling suspended off the concrete soffit by 3" and fixed thereto by rubber/neoprene pads, with the 3" gap packed with 4" fibreglass or rockwool insulation should cure most of the problem. All the edge gaps of the ceiling to the walls and windows must be sealed with an elastomeric sealant (silicone) for it to work properly.
If this is not possible, only a floating concrete floor placed on top of your existing floor, will challenge the problem.
Newer apartment buildings can often have prestressed concrete floors which are often THINNER than traditional reinforced concrete, and this will exacerbate the problem as well as allow more 'bounce' and movement in the floor.
They were on a plywood platform with vibrapods on top of corrugated cardboard. This decoupled the bass from the wood floor and, in so doing, eliminated some booming that I was getting from the floor's resonance. But the platform interfered with the soundstaging which was better with the speaker resting directly on the floor. With Herbie's Big Black Dots, I got rid of the booming and the soundstage remained intact. This solution is easy to apply and pretty cheap, so your neighbors might be willing to go along with the purchase.
"I can hear every note of the bass line of the music played by my downstairs neighbor, but hardly anything else."
I'm just curious as to what conclusion was drawn from this. Are you proposing that the overall level is not too loud for a shared ceiling/floor/wall situation?
> > Are you proposing that the overall level is not too loud for a shared ceiling/floor/wall situation? < <
No--or not just that. First, my downstairs neighbor is a batty spinster woman in her '60s who loves to play loud rock music. She's an angry, unhappy person who's not going to change (fortunately her unit is for sale so maybe she'll be gone soon). On the other hand, if I were to approach her politely and offer her a solution which I pay for (perhaps together with the other neighbors), and which is not too visually intrusive, we might be able to mitigate the problem. In essence, I'm trying to approach this like a grownup.
Second, I DO seem to live in a building where certain (low) frequencies transmit pretty easily through the floors and walls. If I could find a cheap, easily applied solution, I could make it available to others in the building as well.
I guess there is a third reason. I own two units that are joined together. The unit where my system is has no neighbors above or below. So right now I'm lucky. But that situation can't last forever--someone will move in eventually--at which point THEY might start complaining about ME.
CHEERS,
Jim
"In essence, I'm trying to approach this like a grownup."
There is nothing uncivil in making an anonymous call to the police.
"But that situation can't last forever--someone will move in eventually--at which point THEY might start complaining about ME."
Extraneous noise in one's apartment can be torturous. The grownup thing to do is, turn it down or move. Baby steps to make nice is a waste of money.
I'd love to de-couple all these assholes with their obnoxious car stereo noisemakers. You know the guys with small dicks and tons of low frequency noise (I refuse to call it bass) Why oh WHY do they think we ALL want/need to hear rap at 135db at 3:00am? I don't want or need to EVER hear Rap.
...I know the guys your talking about. Never measured their dicks though.
;-)
Jim
> What's the best approach?
Passive vibration isolation works when the resonant frequency of the vibrating component connected by some stiffness to the structure is well below the frequencies you want to isolate. So if you have a speaker generating deep bass of a few tens of Hertz then you need a resonant frequency of a few Hertz or lower.
Suspending the speaker on bungee straps from the ceiling would be cheap and effective.
Sitting the speakers on top of a spring will be less effective because the short distance will dictate a stiff spring.
Wrapping long bungee straps over pulleys attached to a framework would enable one to get soft springs with a standlike structure. It would probably not be difficult to make if you are DIY inclined.
Active vibration isolation is the most effective but is expensive if you are isolating heavy objects because you need to generate large forces.
There are lab standard devices for this and some have been adapted for audio applications in the form of turntable isolation platforms. All include a compliance and a mass (which includes the mass of the object to be isolated). See: http://www.kineticsystems.com/page125.html and http://www.soundsofsilence.com/vibraplane.htm. Another audio-targeted set of devices can be seen at: http://www.stereophile.com/standsracks/500bright/
All these are too expensive for your application since you (and your neighbors) will need many. The DIY approach is to combine a small-diameter pneumatic tube, such as is used in bicycle tires, with a massy plate on which one can sit the device. One can then adjust the pressure in the tube to act as a LP filter below the offending vibration frequency.
The use of foam pads (as in the SubDudes) or resiliant feet/pods (as in the IsoNodes or Sorbothane devices) can be effective, depending on the offending frequencies and the geometry/mass of the device to be isolated.
Kal
Isolating the device or decoupling it will have absolutely no effect on sympathetic vibration, that is the vibrabration you feel in your listening room from your neighbor's stereo. Think of the boom box in the car 50 feet away... you still hear the low frequencies and it is separated by 8 tires, metal, plastic, glass and air.
Once the air in your neighbor's apt moves...decoupling the device that initiated the wave launch will have no effect.
Peter
First you can move the subwoofer really close to you so it doesn't have to play so loud.
I once met a strange person who placed his subwoofer on the couch next to him in his apartment -- so close it didn't have to play very loud and the couch absorbed some bass too.
Next you can locate the subwoofer driver half way between the floor and ceiling to prevent excitation of the first-order axial floor to ceiling standing wave, whose high pressure zone is at the floor, and at the ceiling = perfect to annoy downstairs and upstairs neighbors.
This would work best with an upfiring or downfiring driver.
There would still be plenty of bass output to disturb the neighbors, but at least you wouldn't have a floor to ceiling standing wave potentially resonating with each kick drum hit.
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
Well, first off, I was not speaking of isolating the source. I was speaking about isolating other audio-producing devices which may be vibrating in sympathy from structure-borne energy.
Second, Jim was asking about what "he" could do to his equipment and what other neighbors subject to the same onslaught can do to theirs so that the offending vibrations do not modulate their systems.
Isolation from air-borne energy requires a complete enclosure and is impractical. OTOH, when I was apartment shopping, I looked at one that had an isolated room-within-a-room because the previous owner was a professional drummer and he used it as a practice room. Man, was it quiet but it was also a bit eerie.
Kal
I thought Jim was asking how to alleviate the bass in his (and others) apts from what I read of his post. Kal, the apt building needs individual "panic" rooms..laugh. God bless you NYC philes.
Pete
The reason I bought my apartment was that the moment I walked in and closed the door, it was quiet and I felt isolated from the outside. In nearly 20years, I have had only 2 complaints, both from the same person and both entirely justified. The rooms on either side of my listening room are mine. The folks downstairs are severely hard of hearing. The folks upstairs have kids, so they dare not complain! I have installed an acoustic seal around the apartment door and triple-glazed windows.
That said, I still get asked if someone complains about transmitted noise although I have never been the cause. The real issue is the high degree of consideration and restraint of all the owners.
Kal
Bass energy passing into a building is only bad for the sound if it is someone else's bass energy, or it causes some part of the building to buzz or rattle (annoying room/home noises).
The more bass energy that gets absorbed by the walls, or passes through the walls, the weaker the bass reflections, and the smoother the bass frequency response you will hear.
The best home listening room for bass would have flexible surfaces, or at least one of each pair of opposing surfaces would be very flexible.
= weaker standing waves
= smoother bass
= more bass heard outside your room
= we're back to your original problem:
Most of the bass coming through the walls and floors and ceilings is airborne bass energy, so placing the bass speaker much farther from the room surface the sound is going through will reduce the problem.
Putting a subwoofer on a stand over one foot tall would help, or put it on the couch right next to you, but don't put your arm around it!
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
Monopole woofers pressurize the room and apply force to the walls and ceiling. You will hear this no matter how well isolated the speaker boxes may be from her floor.
The measured frequency response of a dipole bass speaker will be a little smoother,because they are somewhat directional,
and that means to reduced excitation of some standing waves (between the side walls and between the floor and ceiling),
but not that much different,
assuming you want to obtain the same average SPL measured at the listening seat.
The "room pressurization" from dipoles does not differ significantly from monopoles inside an ordinary home listening room.
There might be a difference inside a sealed car where the monopole speaker would get a boost from cabin gain, and the dipole would not,
but there's little or no cabin gain inside a typical home listening room (too big and rarely sealed well enough to be pressurized by a few relatively small speaker cones).
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Richard BassNut Greene
"The Floyd R. Turbo of Bingham Farms Michigan"
Auralex SubDudes are very effective at decoupling and cost around $50.
db
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Bad news is decoupling is probably not going to help with a "downstairs" neighbor (upstairs maybe)
Try offering her some wireless headphones for agreed upon hours.
I'm not so sure you're right--but even if you are, it might help HER downstairs neighbor, so I'm still interested in an answer.
Ideas, anyone?
Jim
I would try a "sandwich" of rigid and compliant materials to go under the subwoofer or speakers . alternating layers of open cell foam and wood boards.
jeff
Thanks Jeff!
Jim
Good luck with that, I don't know how effective a cure it will be in this case since you're above the sound source. This works better when the people below are complaining.
when I lived in a noisy bldg, everyone just turned up their own stereo to keep the neighbors out. I agree that coupling is not the issue for you, but the fact that she's playing it freakin' loud is! Just bang on the floor with a broomstick or call the 50. if it were coupling, a small piece of wood under front of each cab would work.
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