Whether it's worth the cost and effort depends on what you're starting with and what you want to accomplish. If you're driving a Mercedes with factory sound it's not worth doing - may even make things worse. If you're driving a vehicle with bad tires, weather seals or motor mounts it's not worth doing until you fix those problems. Your vehicle may be a perfect candidate for treatment but if you plan to get rid of it in a year or two, it's probably not worth it.
There are two basic reasons to do a sound deadening project:
- The vehicle is noisier than you'd like.
- You want to improve the vehicle's capacity to host a sound system.
Vehicles can be unpleasantly loud inside by design - for economy or performance, the manufacturer chose to eliminate the cost or weight. You may have added performance mods that made the vehicle louder and you want to tame the noise.
It's not possible to make a bunch of steel hurtling down a highway propelled by exploding gasoline absolutely silent. It's easier to reduce noise levels during design and manufacturing than it is as an aftermarket project. Making a noisy vehicle quiet, or at least quieter, is a significant undertaking. It's complicated and time consuming. Anybody can do, but they have to be willing to make the effort. Expect 2-3 days to treat an entire vehicle by yourself. The results can be spectacular, but it isn't going to work for those who just want to throw some stuff down and be done with it.
The treatment for noise reduction - control structural vibration, block and absorb - is the same treatment you'd want for the accurate reproduction of music. Reduce the noise and you reduce the irrelevant information that's getting randomly mixed in with the music.
Think of it like this. You're watching a football game. Your girlfriend or wife is sitting next to you on the sofa talking about curtains. Your girlfriend is the noise, football is the music. If she decides to go take a nap, the football sounds much better //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
Improving the vehicle's capacity to host a sound system is a little more complicated because itcan mean many things. To me it means driving in a quiet car playing my music quite loud and having it sound good. People have compared it to being in a club. I like that //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif I also like being able to play it loud without having to worry about anybody hearing it outside the car. The same thing that keeps noise from being heard from outside keeps music from being heard outside.
The final stop will be SPL competitors. Before I get there, I'll talk about "don't care about noise, just care about loud" - the just fix rattles guys. Don't care about noise penetration or how loud the sound system is to people outside the vehicle. Don't care a lot about the fidelity of the music being played - loud but not sounding like the vehicle is tearing itself apart.
Rattles are always two or more hard objects, one or more of which is vibrating, causing intermittent contact with the other hard body(ies). You can either stop the objects from moving or you can put something between them so they can't make contact. The latter is almost always the direct approach. The rear license plate on a sedan with a sub in the trunk is a very good example. They always rattle.
The indirect approach is to add a ton of vibration damper to the rear of the trunk, trunk lid, or whatever part of the car the license plate is attached to. The direct approach is to glue a layer of closed cell foam to the back of the license plate itself. 100% solution.
That isn't to say that applying vibration damper to the sheet metal won't limit the energy available to drive the rattles, it will. I am saying that vibration damper is an inefficient way to stop rattles. Vibration damper is best used to stop sheet metal vibration that transfers noise through the vehicle and creates another noise source - audible resonance.
Finally, if you are only interested in SPL, you're strictly chasing numbers, no sound deadening product is of any use to you.