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Products and Information to Tame Your Vehicle's Acoustics

As many of you know, I've been testing and reviewing sound deadening products since 2005. I first became interested in the topic because my car was unpleasantly noisy and later because I wanted to improve the sound of the aftermarket stereo I installed. My question in the beginning and the one I’ve been asked most often is: How can I get great results with as little cost and effort as possible? It turns out that the answer is the same as it is for most projects: Use the right tool for the job.

I won’t be reviewing other products any more since I'm now offering my own. I will be explaining how and why to use these products in the most effective and efficient manner possible. Whether you ultimately decide to use the materials I'm selling on this site or not, my goal is to provide you with all the information you will need to make your choice and complete your project successfully. I'll provide two paths through this information - a simple "tell me what to do" approach and an in-depth explanation for those of you who are interested.

What I've Learned and What You Need to Know

Imagine you are driving on the highway and a very noisy truck is right next to you. Noise from the truck is coming at you through your vehicle's door and it's loud. There are three possible ways to stop the noise from reaching your ears.

The first thing you will notice is that the noise from the truck is making the door's sheet metal vibrate - essentially turning it into an unwanted speaker that is right next to you. Apply a vibration damper like CLD Tiles to stop the vibration. CLD Tiles have been designed to work with minimal panel coverage. That means you will need to do less work and the project will cost you less.

After you have stopped the sheet metal from vibrating you have two possible strategies left to deal with the noise that is still coming through the door. One possibility is to absorb the sound. Unfortunately, absorption isn't practical in a vehicle. The lower the frequency you need to absorb, the thicker the absorber needs to be. Road, engine and exhaust noise are deep (low frequency) sounds. To be effective, you would need an absorbent material between ten and seventy inches thick. Right, never going to happen.

Fortunately, the third option works perfectly in the space we have available. Block the noise. In exactly the same way the barrier wall along the highway is protecting the houses behind it from the truck noise that's coming through your door and driving you crazy, you can do the same thing, on a much smaller scale, using Closed Cell Foam and Mass Loaded Vinyl.

It's really that simple. For years, we've been going about this all wrong - using layer after layer of "sound deadener" and getting poor results. Use the right tool for the job.

Defining Some Terms

Before we can get anywhere, we need to make sure we are talking about the same things. "Sound Deadener" is a vague term that describes a range of materials and techniques. It has traditionally been used when referring to vibration dampers - a specific class of products designed to control resonance in panels. I'll be referring to these products as vibration dampers.

Everything we are trying to do comes down to sound. Whether we are trying to quiet a vehicle, improve its ability to host a music system or both, it's all about sound and controlling what reaches our ears. Sound is almost devious in its behavior so we need to understand a little bit about how it moves around before we can control it.

Stock vibration damper on the front passenger side floor.

When it comes to noise control we are concerned with engine, exhaust, tire in contact with road surface, and wind - from our vehicle and from all of the other vehicles around us on the road. We may also be concerned with noise created by the music we play as it interacts with the vehicle around us. Some of this noise is transmitted directly through the structure of the car. Some of it travels through the air before it passes through the vehicle panels and glass on its way to our ears, often times exciting panel resonance that creates a secondary noise source.

The first step in any successful noise control or acoustic improvement project is minimizing panel resonance. It doesn’t really matter if the existing resonance is caused by vibrations directly introduced by the engine, exhaust and suspension or if it is being driven by airborne sound. Resonating panels are important routes for transmitting and reinforcing noise.

This is where vibration dampers come in. Your vehicle most likely came from the factory with at least some vibration damper applied. Unless yours is a luxury vehicle, or even if it is and you have added an aftermarket sound system that takes the vehicle beyond the original design specifications, you will want to add more vibration damper. OEM applications favor reducing weight and cutting costs beyond all else. In our zeal to quiet our vehicles, many of us took this too far in the opposite direction - applying multiple layers of vibration damper to every bit of sheet metal in the vehicle. I'll tell you something that no one else selling vibration dampers will - this is wasteful and counter-productive. Put images of shiny silver vehicle interiors out of your mind. When it comes to vibration dampers, anything more than 25% coverage is excessive. Beyond that, you are wasting time and money, making it difficult to refit trim panels and potentially making the vehicle more difficult to service in the future - you are using the wrong tool for the job.