Sound Deadener Showdown
Version 2 Updated: October 22, 2005
Products Reviewed: B-Quiet Extreme and Ultimate, Brown Bread, Cascade Audio Engineering VB2, Dynamic Control Dynamat Original and Dynamat Xtreme, Elemental Designs eDead v1 and eDead v1SE, FatMat, RAAMaudio RAAMmat BXT, Second Skin Damplifier and Damplifier Pro,
How To
Define your goals. Different vehicles have different strengths and weaknesses. Different people have different tastes, budgets and interests. Figure out what you want to accomplish and how much time and money you are willing to commit.
A note on Rattles
Is sound deadening mat the best way to treat rattles? Maybe. A rattle is the result of two solid objects hitting each other. It is possible that applying one of these products will stop a rattle, either by immobilizing the two solid objects, or by reducing the vibrations that are causing them to hit each other in the first place.
A more effective approach is to identify the source of rattles and treat them prior to installing the mat. Make sure all parts are tightened down. Wrap wires in foam tape at the point where they contact sheet metal. Rear license plates and spoilers are notorious source of rattles.
The important thing to avoid is sealing a rattle away so that you can't get to it.
What is Most Important to You?
The Loudest System in Town
I don't mean being able to set off car alarms from two blocks away. If that's your goal, tear out the OEM sound deadening materials and drill some vent holes in your trunk. Mount some nice blue flashing lights on the roof and call it a day.
No, I'm talking about achieving maximum Sound Pressure Levels inside the vehicle. The concept is simple, don't let any sound out of the passenger compartment and eliminate everything that that dissipates or diverts sound waves before the reach your ears or meter. It is probably most important to reinforce and dampen the sheet metal. While noise free sound isn't your top priority, reflections can cancel source waves and reduce their strength.
Damaging your hearing and testing the effects of sound waves on the human nervous and cardiovascular system takes careful planning and a lot of trial and error.
Luxury Car Comfort
The most striking aural difference between getting into a Toyota Tercel and a Lexus LS (substitute any economy and luxury car) is the sense of separation from the outside you get when you close the door of the Lexus. You may be parked next to an active construction site, but when that Lexus door closes with a solid thump, it is almost as if a switch has been thrown.
You will still hear the loudest noises from outside, but the din will be all but eliminated. The contrast between outside and inside is palpable and dramatic. Do the same thing in the Tercel and you may find yourself checking to see if your windows are closed.
Proper treatment will close, possibly even eliminate the gap. When luxury cars are designed and built, every route that noise can take is addressed. Economy cars demand that cost and weight be given priority. Every vehicle fits somewhere along this continuum.
When I first bought my Honda Civic EX sedan, I knew it was noisy, but I really didn't care. I loved the car, it fit my requirements perfectly and a quiet passenger compartment never even entered the equation.
The first problems I encountered were all noise related, but I didn't know there was anything I could do about it. To listen to a CD or the radio while driving, I had to turn the volume up to the point of distortion - I was listening to bad sound combined with the ambient noise. Using my cell phone was a challenge. I found myself almost shouting to be heard and having to strain to hear.
Most people don't consider the consequences of a noisy environment. We are where we are, it is what it is and that's that. The fact is, noise has a negative impact on us in a variety of ways. It causes fatigue and stress, neither of which is pleasant and both of which are potentially dangerous when driving. Isn't it great that we can do something about it?
All we have to do is stop noise from entering the passenger compartment. Whether the source is our engine or tires, wind or traffic, we block what we can and absorb what we can't block. Noise either passes through the shell of the vehicle or it is transmitted by causing vehicle components to vibrate, becoming sound waves when they reach the air space around us. Once they get inside, things get worse as they reflect off the hard surfaces inside.
The primary function of the sound deadening mats tested here, is to stop vibrations from being transmitted through the sheet metal that makes up most of a vehicle's skin. They add mass, lowering the frequency of the vibration below the threshold of human hearing, and their viscoelastic adhesive damps vibrations, ideally to extinction.
They also have some barrier properties - some of the sound that tries to pass through them will be reflected back. Finally they add a small amount absorption - some of the sound that tries to pass through them will not be able to make it all the way through.
Vibration damping is the first step in noise control. You will very likely notice a difference if this is the only step you take. To get the best results, you will need to use additional products in a literally layered application. First apply the damping material and then add barriers and absorbers as needed. Lead foil and mass loaded vinyl are common pure barriers and acoustic foams and natural or synthetic fibrous products are useful absorbers. You can buy composites that consist of layers of barrier and foam, ready to apply in one step. Some even have an adhesive with release paper. Peel and stick.
Ultimate Sound Quality
Pursuing Sound Quality can be an obsession. Selecting the finest system components and installing them perfectly will never get you to your objective if you don't pay at least as much attention to the acoustics of the vehicle.
Start with the panels we addressed in the SPL section, add noise reduction and possibly extra absorbers and you will be well on your way to a great SQ setup. By reducing sound energy loss, blocking noise from the outside and absorbing distortion inducing reflections inside the vehicle, you are cleaning up the sound you hear and lowering the noise floor with which the sounds you want to hear have to compete - any sound system will sound better and use less power.
Basic Application Procedure
The specifics of each area are slightly different, but the basic process is the same. Remove any trim, seats, carpeting, or whatever is covering the sheet metal or plastic you want to treat. Vacuum out any dirt and dust and then wipe the area with denatured alcohol. Acetone will work, but it will remove paint, so be careful. You now have a dirt and grease free surface ready to take some sound deadener.
Start with any easy - flat, large area like part of your trunk. Cut off a piece about 8" long - I prefer a pair of heavy shears, but most people like a utility knife. With a little practice you will be able to work with pieces a foot or more long.
Peel the release paper off the first inch or so and fold it back. Now you have a piece of mat with an inch of adhesive exposed and the rest still covered with the release paper. Ready, aim, fire. Line the piece up and press the exposed adhesive down on the surface. The mat is now positioned where you want it and if not, you will still be able to get it off. Good spot? OK, start pulling the release paper down the length of the mat, pressing the exposed adhesive onto the surface as you go. Voila! First piece down. Do that a few hundred more times and you are done.
You want to use the largest piece you can for each application - but not too big. You will quickly learn what too big is, because in your impatience and growing confidence, you will finally get to the point where you exceed your capabilities and the laws of physics. You will lose control and get a bubble or a fold or something you didn't intend. No problem, take your knife and cut the bubble or fold out, press it down and all will be well. You want to have perfect contact between the mat and the surface you are attaching it to. Your utility knife and an X-Acto knife will be your friends.
While you don't need a heat gun or a roller, they may help. If you are using Peel & Seal, or one of the asphalt mats sold for automotive use, ignore the advice of the seller. If you are wearing anything heavier than a t-shirt, you must use something to warm the substrate, warm the mat and then warm the installed mat before you roll it. Be careful not to melt the adhesive or you might be accelerating the deterioration of the asphalt. At any temperature warming to about 120°F will improve the adhesion of an asphalt product. Butyl adhesives are no where near as tricky. If they are flexible enough to install, they will stick. I got a nice roller at Home Depot for wallpaper - rubber handle, plastic roller, $5. Really helps for pressing down on flat areas, and it gives you something to do while you figure out where to go next, so you don't just sit there looking dazed.
As you apply sound deadener, rap on the panel with your knuckles or a small rubber mallet. You will be able to hear the change in resonance. After you apply a layer, tap some more. This will help you determine where you need to add layers. Tap, apply, tap apply, until you are satisfied with the result.
Make a commitment
Don't imagine, like I did, that you can do the whole car in a day. Imagine you can do it in 5. If you think you might need your car during that time or have to do something crazy like going to work or school, do it in pieces. Trunk one day, doors another, then the rest when your wife is visiting her mother in Ireland and you can take a few vacation days that you have been hiding - even then, she is going to come home and find your front seats in the living room, or was that just me?
Next time, I'll be smarter (maybe). If you are lucky enough to be able to take the car out of operation for a week or three, and do it in a garage, go for it!
Doors
Your doors might be the best place to start - tricky, but probably the most dramatic effect. The simplest treatment is to apply a 10 or 12 inch square of damping mat behind the speakers in your car doors. This will reduce the resonances in the door sheet metal and have some effect on reflected sound waves that interfere with the sound you really want to hear. Several manufacturers sell "Door kits", and that's all they are, two squares of mat.
The next step up from this most basic installation is a full treatment to the doors containing speakers, in which you fully cover and seal the inner and outer door sheet metal creating what amounts to a proper speaker enclosure. Fully cover the inside of the outer skin with mat. Describing the sheet metal components can get confusing. By inside of the outer skin, I mean the sheet metal you can touch and see from outside the car - the painted part. By inside surface, I mean the surface facing the interior of the car - you probably don't want to apply deadener to your exterior.
This is pretty awkward since you have to work through the access holes from the interior side. An argument could be made that practicing on an easier area first might make sense. You will need to use fairly small pieces to fit them through the holes, so it can get tedious. Take your time and be thorough. If you have speakers in your doors, this is the surface that will be hit by the back wave.
When you are satisfied that you have applied enough mat to control vibrations, it is time to consider adding additional materials. At a minimum, consider adding at least one layer of closed cell foam directly behind the speaker. This will help absorb the sound waves coming from the back of the speaker. Better yet, apply the foam to the entire surface with extra layer(s) behind the speaker. You may want to consider a barrier product here too, but you will get very good results with just the mat and foam.
I specifically said closed cell foam for inside the door because it is resistant to water and mold growth. Ensolite and Neoprene are closed cell foams. Rain flows through your doors, so anything you put in there should not absorb or be damaged by water.
Now we can move on to inner sheet metal, what you were just reaching through the access holes in for the last stage. You will get the best result if you seal all of the openings - not the speaker mounting hole - to seal the door completely. If you do this, you can throw away the plastic moisture barrier you removed to get inside the door. Be careful to leave enough area uncovered along the edge so that you can fit the trim panel back on when you are done.
There are wires and mechanisms that pass through this surface, and you want to protect them. Using split loom or plastic tubing will be fine. Just laying mat over the larger holes will probably not be sufficient. I like to use aluminum flashing from a roofing supply or hardware store. I just bough a roll, 14 inches wide by 10 feet long for $8.00. It is thin enough to cut with tin snips or heavy shears, but rigid enough to do the job.
Take a piece of paper larger than the opening and trace the shape you need - making it as much larger than the opening as you can, an inch all the way around is probably ideal. Use a little bit of spray adhesive to attach your template to the flashing and cut. Peel off the paper and you are ready to go. Some people like to use self tapping screws, I prefer to use silicone sealant. Seal it up, tape it in places and let it set up for an hour or so. Remove the tape and cover it with mat.
Add mat to entire door surface until you have the vibrations under control. Another layer of closed cell foam is very nice. If you are really confident that you have created a moisture proof barrier, you can use open celled acoustic foam instead. If you are using a separate barrier, this surface will probably be a more effective and easier place to put it.
Next, door trim panel. These are usually plastic and can benefit form some mat. You won't need as much as you did with sheet metal. One layer or less may be enough. My panels had large square foam blocks that went through a hole in the sheet metal. I knocked them off and peeled off the carpet padding type fiber mat that was hot glued in place. Layer of mat, layer of closed cell foam, and then I filled all of the space I could with open cell acoustic foam. Nice.
Well, that door's done. Do it a few more times. All doors done? You can either move on to the next section, if that is your intent, or, if your car is drivable, take it out for a spin. Listen to what has happened.
Trunk or hatch
Depending on your system configuration and goals, treating the trunk or hatch area may be more important than treating the speaker enclosing doors. An amplified sub-woofer can generate a tremendous amount of sound pressure, flexing sheet metal panels, sending sympathetic resonances throughout the vehicle and causing anything that isn't padded and firmly attached to rattle like mad.
Every surface is a good candidate for treatment. If you are concerned with noise, pay extra attention to the wheel wells. These are a major source of trouble, both front and back.
Floor and Firewall
The vehicle floor consists of a lot of sheet metal. Since it faces the road, it is a problem for road noise. Since the exhaust system runs underneath, the problem gets worse. The firewall is all that separates you from the engine, tough to get to, but it can make a huge difference.
The floor is probably the most time consuming surface to expose. Most of the interior has to come out. By being a little creative, you can do it in sections. Maybe front and back, maybe left and right. Because so much is mounted to the floor, you need to be careful not to build the mounting points up to the point that you can't reattach what you took off. This isn't as much of a problem as it might otherwise be, because much of the trim is mounted on the sides, where the structure is most rigid.
Be very careful when removing seats with airbags in them. Yellow loom or wire means airbag! You must disconnect the negative battery terminal before disconnecting these or any other electrical connections. Failure to do this will probably result in at least a blown fuse. Many cars will require a trip to the dealer to reset the airbag warning light. In the worst case, you can be killed by a deployed airbag.
Roof
There is some debate as to how effective treating the roof is. In any case, it is a large area of sheet metal that is subject to flexing and resonance. It can also be very loud in the rain. Each vehicle is different and you will have to decide if it is worth dropping the headliner.
How Many Square Feet?
Now that you have decided what areas you are going to tackle, it is time to figure out how much material you will need. I think a good minimum for deadening mat is 1.5 times the total square feet you plan to treat. If you will be doing both sheet metal surfaces and the trim panel for your doors, then that counts as three times the area of the door. Add it all up, multiply by 1.5 and round up. It's better to have a little too much than not quite enough. You can also give the leftovers to a friend, or use them to line that computer case that makes such a racket.
A similar calculation for foam should also get you close to the mark. If you use a barrier, you are not likely to double it up.
Summary
For maximum results (and with maximum effort and expense) treating the entire vehicle is the way to go. Floor, firewall, wheel wells, doors, trunk, and roof are all candidates. It is entirely possible to use several hundred square feet of mat in an application like this.
If you like doing crazy things, you'll love this. Even if you hate doing crazy things, you are going to love the results.