AmIGrand
09-17-2003, 02:42 PM
Alright, first of all, I must apologize, I have promised this thread for a long time aned never got around to writing it. So, here it is, tips & tricks of making your car rattle free. Also note that the title of this thread is "Sound damping and vibration elimination", not Sound DAMPENING. Damping means to damp, to reduce vibration. Dampening means to make damp, to make wet. Unless you're asking how to spray your car with water, get it right, or I WILL give you sh!t about it. :D
Before we get into materials and whatnot, a few words on how this stuff works, and what we want to accomplish. Every object in the physical universe has a resonant frequency. When subjected to energy at or close to that frequency, the object in question will absorb as much energy as it needs to begin vibrating. What we percieve as an annoying noise has another side effect to the audio world - it's reducing sound energy. In other words, however much power it took to start that object vibrating, is energy that was absorbed from your speakers output, and ain't makin' it to your ears or the competition mic. We're trying to reduce and/or eliminate both the annoying rattles this causes, and increase the amount of energy we get to hear. There are a few ways to accomplish this.
Now we get into various materials, tools, and techniques. I will mention the absolute MOST IMPORTANT thing you will need to properly quiet your car down first.
PATIENCE
And lots of it. If you hurry through it, you will not accomplish what you want. If you don't have several hours to dedicate to the job, do it in sections, with a plan. Trunklid today, rest of the trunk next week, doors after that, etc. Expect to spend at LEAST a full day to do a full car. Got it? Good. Moving right along....
Mass Loading
This is the most common method of reducing vibration. This is what all those different kinds of mat and sprays are really about. By adding mass, we increase the amount of energy required to make a given object vibrate. Any amount of energy less than the "vibration threshold" is simply reflected, and for our purposes that's a good thing. The products in question have the additional ability to transform vibration energy into heat energy, further reducing vibration if and when the threshold for the treated object is reached. But there are some situations where this doesn't cut it! Common types of mass loading materials are:
Asphalt or vinyl mat. The first question everybody asks is, "what brand of mat should I get?" The answer is - depends on what you want to accomplish. Dynomat more or less started the whole idea of a specialty mass loading material, and in my experience, is still the best. Other brands are out there, and many of them are very good. There are also materials "designed" for other uses that work well in this capacity as well.
Many of the products out there are asphalt based. It does the job. It's also heavy, smelly, tends to stiffen up and crack over time, and will eventually fall off. Keep that in mind when shopping. Vinyl based products are lighter, just as effective, and last a LOT longer, not to mention they don't stink when applied, or months later when your car is sitting in the sun. :E Some mats have multiple layers, some have metal backing. For the most part, they will indicate what they are designed for, you should pay attention. Some are designed for application to the floor to reduce road noise, some for apllication to interior metal, some for sheetmetal. All will work, but some better in one app than another.
Application. Too often I see trunk lids with sheets - somtimes several thick - haphazardly "ironed" on underneath. Those with a little more patience will take the time to form fit the stuff, but it's still "sheeted" on. Folks, take the time to cut & paste. Small, perfectly fitted pieces laid carefully into full contact will work better, and won't come loose over time. This goes for the whole car. Use as big a sheet as can be applied without any gaps or air pockets underneath. When you reach a rib of metal that the sheet will have to cover, cut it and start another piece on the other side. It looks better, works better, and lasts longer.
Sprays. I personally think these are a total ripoff. Do they work? Kinda. They are OK for areas that just can't be reached to apply mat. But they are NOT as effective, any brand, no matter what they claim. When used as a base over which mat will be applied, fine. This will allow you to spread the spray over an area that is oddly shaped and difficult or impossible to mat, and use a few pieces of carefully cut mat to supplement it. Used alone, these products are as close to useless as you can get, unless you want to use 2 full cans on one door panel.
Active Absorbtion
If two objects are near each other, and one or more of them vibrates enough to come into contact with the other one, "vibration" turns into "rattle". One of the most common aggrevations to people who spend mony on damping material is that the "rattles" they sought to eliminate are reduced, but still very much present! The reason is simple. The mat may have reduced the vibration, but not enough to completely prevent all motion. And the mat materials are generally applied to the surface, not BETWEEN the objects making the noise. Active absorbtion is a fancy way of saying we stuff something between teh objects to absord the vibration energy and prevent physical contact between vibrating objects. The stuff used here is less "technical" than the mass loading materials; various foams and silicates are best. Properly applying them is a whole different matter, though....
Foam tape. This is a personal favorite of mine, and one that many people, including professional installers, overlook. Go to a hardware store, and get the foam weatherstripping they sell for window and door sealing. Use small pieces of it on the underside of interior trim panels, along the edges of 3rd brake lights that contact glass - right at the contact spot where anything is rattling against something else!! Especialy usefull for wire loom runs under the rear deck and behind the dash. Can't be beat.
Expanding foam. BE CAREFUL!! Improper application of this stuff can do SERIOUS damage to your car! Once exposed to air, this stuff will expand until it's done, PERIOD. If that means a spot weld is in the way - well, too bad for the spot weld. If the weld is stronger than the sheetmetal to the outside of it, so be it - you now have a car with a bad case of the mumps as the body panels deform around the foam. I've seen it happen, don't let it happen to you. Get the "low expansion" type, and apply it slowly and carefully. Use this anywhere where there is an open space that can't be reached with other materials. Under the trunk lid is a perfect example. The sheetmetal is braced underneath by a "skeloton" of bent metal. This is usually spot welded on, leaving a very small gap along the edges. When the sheetmetal begins to vibrate, it slaps against the less-flexable bent steel! One can't get mat stuck in there very well, and spray won't cut it. Expanding foam injected in there works wonders.
Silicone sealant. Another oft-overlooked wonder of the damping world. If you read the example above, try this: Instead of expanding foam under there, shoot a nice bead of silicone along and into the gap. Bingo! No more rattles. The foam works better in areas too large for the silicone to fill, but in narrow gaps, this stuff rocks.
Good ol' fashioned foam stuff. Sometimes a piece of foam stuffed under something just can't be beat. Under the reart decklid trim, for instance. Again, don't just stuff a big piece under there and hope everything fits. Cut a piece to fit where the rattel is present.
OK, that about covers it. Take the time to crawl around your car with the stereo cranked and identify the rattles one at a time. Once you find one, decide which of these techniques and materials will do the job best. Then apply it, carefully. Start with the exterior, under the car, the license plates, spoiler, bumper clips, etc. - all common causes. After that's handled, move inside. Strip out the interior, and apply the base you will use on sheetmetal and whatnot. Now put the interior back together, and listen for trim panels and whatnot that rattle. There's an order of events here.
Now begins the conversation about what brands everyone thinks are best, where to get deals, other techniques and materials, etc. That's what this thread is for, so have at it! Please keep it on topic and constructive, please, as this is a sticky for people with specific questions and needs. :thumbs:
Before we get into materials and whatnot, a few words on how this stuff works, and what we want to accomplish. Every object in the physical universe has a resonant frequency. When subjected to energy at or close to that frequency, the object in question will absorb as much energy as it needs to begin vibrating. What we percieve as an annoying noise has another side effect to the audio world - it's reducing sound energy. In other words, however much power it took to start that object vibrating, is energy that was absorbed from your speakers output, and ain't makin' it to your ears or the competition mic. We're trying to reduce and/or eliminate both the annoying rattles this causes, and increase the amount of energy we get to hear. There are a few ways to accomplish this.
Now we get into various materials, tools, and techniques. I will mention the absolute MOST IMPORTANT thing you will need to properly quiet your car down first.
PATIENCE
And lots of it. If you hurry through it, you will not accomplish what you want. If you don't have several hours to dedicate to the job, do it in sections, with a plan. Trunklid today, rest of the trunk next week, doors after that, etc. Expect to spend at LEAST a full day to do a full car. Got it? Good. Moving right along....
Mass Loading
This is the most common method of reducing vibration. This is what all those different kinds of mat and sprays are really about. By adding mass, we increase the amount of energy required to make a given object vibrate. Any amount of energy less than the "vibration threshold" is simply reflected, and for our purposes that's a good thing. The products in question have the additional ability to transform vibration energy into heat energy, further reducing vibration if and when the threshold for the treated object is reached. But there are some situations where this doesn't cut it! Common types of mass loading materials are:
Asphalt or vinyl mat. The first question everybody asks is, "what brand of mat should I get?" The answer is - depends on what you want to accomplish. Dynomat more or less started the whole idea of a specialty mass loading material, and in my experience, is still the best. Other brands are out there, and many of them are very good. There are also materials "designed" for other uses that work well in this capacity as well.
Many of the products out there are asphalt based. It does the job. It's also heavy, smelly, tends to stiffen up and crack over time, and will eventually fall off. Keep that in mind when shopping. Vinyl based products are lighter, just as effective, and last a LOT longer, not to mention they don't stink when applied, or months later when your car is sitting in the sun. :E Some mats have multiple layers, some have metal backing. For the most part, they will indicate what they are designed for, you should pay attention. Some are designed for application to the floor to reduce road noise, some for apllication to interior metal, some for sheetmetal. All will work, but some better in one app than another.
Application. Too often I see trunk lids with sheets - somtimes several thick - haphazardly "ironed" on underneath. Those with a little more patience will take the time to form fit the stuff, but it's still "sheeted" on. Folks, take the time to cut & paste. Small, perfectly fitted pieces laid carefully into full contact will work better, and won't come loose over time. This goes for the whole car. Use as big a sheet as can be applied without any gaps or air pockets underneath. When you reach a rib of metal that the sheet will have to cover, cut it and start another piece on the other side. It looks better, works better, and lasts longer.
Sprays. I personally think these are a total ripoff. Do they work? Kinda. They are OK for areas that just can't be reached to apply mat. But they are NOT as effective, any brand, no matter what they claim. When used as a base over which mat will be applied, fine. This will allow you to spread the spray over an area that is oddly shaped and difficult or impossible to mat, and use a few pieces of carefully cut mat to supplement it. Used alone, these products are as close to useless as you can get, unless you want to use 2 full cans on one door panel.
Active Absorbtion
If two objects are near each other, and one or more of them vibrates enough to come into contact with the other one, "vibration" turns into "rattle". One of the most common aggrevations to people who spend mony on damping material is that the "rattles" they sought to eliminate are reduced, but still very much present! The reason is simple. The mat may have reduced the vibration, but not enough to completely prevent all motion. And the mat materials are generally applied to the surface, not BETWEEN the objects making the noise. Active absorbtion is a fancy way of saying we stuff something between teh objects to absord the vibration energy and prevent physical contact between vibrating objects. The stuff used here is less "technical" than the mass loading materials; various foams and silicates are best. Properly applying them is a whole different matter, though....
Foam tape. This is a personal favorite of mine, and one that many people, including professional installers, overlook. Go to a hardware store, and get the foam weatherstripping they sell for window and door sealing. Use small pieces of it on the underside of interior trim panels, along the edges of 3rd brake lights that contact glass - right at the contact spot where anything is rattling against something else!! Especialy usefull for wire loom runs under the rear deck and behind the dash. Can't be beat.
Expanding foam. BE CAREFUL!! Improper application of this stuff can do SERIOUS damage to your car! Once exposed to air, this stuff will expand until it's done, PERIOD. If that means a spot weld is in the way - well, too bad for the spot weld. If the weld is stronger than the sheetmetal to the outside of it, so be it - you now have a car with a bad case of the mumps as the body panels deform around the foam. I've seen it happen, don't let it happen to you. Get the "low expansion" type, and apply it slowly and carefully. Use this anywhere where there is an open space that can't be reached with other materials. Under the trunk lid is a perfect example. The sheetmetal is braced underneath by a "skeloton" of bent metal. This is usually spot welded on, leaving a very small gap along the edges. When the sheetmetal begins to vibrate, it slaps against the less-flexable bent steel! One can't get mat stuck in there very well, and spray won't cut it. Expanding foam injected in there works wonders.
Silicone sealant. Another oft-overlooked wonder of the damping world. If you read the example above, try this: Instead of expanding foam under there, shoot a nice bead of silicone along and into the gap. Bingo! No more rattles. The foam works better in areas too large for the silicone to fill, but in narrow gaps, this stuff rocks.
Good ol' fashioned foam stuff. Sometimes a piece of foam stuffed under something just can't be beat. Under the reart decklid trim, for instance. Again, don't just stuff a big piece under there and hope everything fits. Cut a piece to fit where the rattel is present.
OK, that about covers it. Take the time to crawl around your car with the stereo cranked and identify the rattles one at a time. Once you find one, decide which of these techniques and materials will do the job best. Then apply it, carefully. Start with the exterior, under the car, the license plates, spoiler, bumper clips, etc. - all common causes. After that's handled, move inside. Strip out the interior, and apply the base you will use on sheetmetal and whatnot. Now put the interior back together, and listen for trim panels and whatnot that rattle. There's an order of events here.
Now begins the conversation about what brands everyone thinks are best, where to get deals, other techniques and materials, etc. That's what this thread is for, so have at it! Please keep it on topic and constructive, please, as this is a sticky for people with specific questions and needs. :thumbs: