Damping vs. Blocking vs. Insulating: What's the Difference?

“Sound deadening” is one of those terms that gets used to describe just about anything you put inside a vehicle to make it quieter. That's understandable, as it’s the end-result that matters, right? Well, sort of.

Different materials solve different noise problems, and understanding the difference can save you from covering your entire vehicle in the wrong product and wondering why it didn't work. When you're trying to make a vehicle quieter, there are three basic jobs to think about; damping; blocking; insulating. They work together, but they aren't interchangeable.

 

Damping: Stop the panel from making noise

Think about a piece of sheet metal. Tap it with your finger and it makes a sound. Now imagine that same sheet metal vibrating and resonating every time you hit a pothole, close a door, or turn up the stereo. That's where damping comes in.

A damping material is designed to reduce the vibration of the panel itself. Instead of allowing the sheet metal to resonate like a drum, the damping material absorbs some of that vibration and turns the energy into a small amount of heat. We call that mass-loading; we’re literally adding weight to the surface, so that moving it (with vibrations) requires more energy.

Boom Mat Damping Material is particularly useful on large, relatively thin metal panels such as doors, floors, roofs, quarter panels, and trunks. And you don't necessarily need to cover every square inch. The goal isn't to make the entire vehicle several pounds heavier just for the sake of it. Strategic coverage of the areas that are vibrating can make a significant difference.

If your problem is “this panel is buzzing, drumming, or resonating,” start with damping.

 

Blocking: Keep the noise from getting through

Damping and blocking are not the same thing. Damping material deals primarily with vibration in the structure. A blocking material is there to stop sound from traveling from one side of a barrier to the other. Think about the difference between tapping on a door and hearing traffic outside your house. The door itself may not be vibrating very much, but sound is still getting through it.

That's where a sound barrier comes into play. In a vehicle, blocking materials can be useful when you're dealing with airborne noise from things such as the exhaust, road, tires, or the vehicle's surroundings. This is particularly important when you're trying to quiet the cabin.

A heavy, dense barrier can make it much harder for sound energy to pass through the floor, firewall, doors, or other panels. So, if your problem is “I can hear the noise on the other side of this panel,” you're thinking about blocking.

 

Insulating: Slow down heat

Then there's insulation. This one is easy to confuse with the other two because insulation can also make a vehicle quieter. But its primary job isn't necessarily sound control.

Thermal insulation is designed to slow the transfer of heat. That's why a product can be excellent at keeping a hot exhaust pipe from cooking the floor without being the best choice for reducing road noise. DEI has a variety of products designed around this principle, including products intended for floors, tunnels, firewalls, and other areas where radiant or conducted heat is a problem.

If your problem is “this area is getting too hot,” you're thinking about insulation or heat shielding.

 

So why are there so many products?

Because your vehicle doesn't have one single noise problem. A door can vibrate. The road can create airborne noise. The exhaust can radiate heat through the floor. The tire noise can travel through the wheel well. The result you experience is simply “It's too loud.” That's why it's tempting to find one product and put it everywhere.

But a vehicle is a system, and the best results usually come from addressing each problem with the appropriate material.

What if I want less road noise?

Road noise is a good example of why this distinction matters. Start with the source and the path the noise is taking. Damping material can reduce the vibration of the floor and other panels caused by the road. A sound barrier can then make it more difficult for airborne noise to enter the cabin. Depending on the application, additional insulation can also help with the overall comfort of the vehicle. You're not necessarily choosing one of the three. You're choosing the combination that addresses the actual problem.

What about exhaust noise?

If you're hearing exhaust noise inside the cabin, first determine where it's coming from. If the exhaust is physically vibrating against the vehicle, adding sound-deadening material isn't going to fix the mechanical problem. If the exhaust is simply loud and that sound is traveling through the floor or firewall, damping and blocking materials can help reduce what makes it into the cabin. And if the exhaust is also making the floor hot, now you're dealing with a thermal problem too. One source can create multiple problems. That means you may need multiple solutions.

And what about heat?

This is where people sometimes get themselves into trouble. A material that works well for sound isn't automatically the right material for heat. If you're trying to keep radiant exhaust heat away from a floor, firewall, wiring harness, or intake, use a product designed for that job.

Likewise, don't assume that wrapping a hot exhaust component in a sound-deadening material is a good idea; it isn't. The product needs to be appropriate for the environment where you're installing it.

The simple way to remember it is if you're trying to figure out what you need, ask yourself three questions:

• Is the panel vibrating? Think damping.
• Is sound traveling through the panel? Think blocking.
• Is heat traveling through or radiating toward the panel? Think insulating or heat shielding.

 

• Is the panel vibrating? Think damping. Sheets of Boom Mat, Boom Mat XL, and Boom Mat Flex, as well as the spray and brush-on versions are designed to reduce panel vibration and the noise it creates. ATAC will help here, too, while also bringing in some heat insulation at the same time.
• Is sound traveling through the panel? Think blocking. Sound Barrier and Under Carpet both add mass between the noise source and the cabin to help block sound transmission.
• Is heat traveling through or radiating toward the panel? Think insulating or heat shielding. Floor & Tunnel Shield, Form-A-Shield, Form-A-Barrier are designed for different types of heat exposure and applications in the engine bay and exterior, while Under Carpet Lite and ATAC are your go-to options in the cabin.

And if you're dealing with more than one of those problems, there's nothing wrong with using more than one type of product. That's actually the whole point. The best sound and heat-control systems don't rely on one material trying to do everything. They use the right material for each part of the problem. Once you understand the difference between damping, blocking, and insulating, choosing the right DEI product gets a whole lot easier.