Car Audio

LIS Audio How-To: Benefits of Auto Sound Deadener



  Sound deadener has been very popular amongst audiophiles and bass heads for many years in the mobile electronics industry. One of the most recognized names in sound deadener is HushMat, which is headquartered in Olathe, Kansas. There are lots of benefits to using sound deadener, or as we refer to it at LIS Audio “Sound Treatment,” which we will be delving into in this article.

We will discuss the advantages, disadvantages, and properties of sound deadener, as well as how it applies to different vehicles across various applications. The uses of sound treatment in it’s versatility goes beyond being used in automobiles, but offers advantages in UTVs, motorcycles, boats, RVs, really almost any type transportation.


For many years the most familiar name associated to sound deadener was Dynamat, which was one of the very first companies to properly promote the advantages of their product in the mobile electronics market. In the past the main duties of adding this material to a vehicle helped to accomplish two goals, less external noise reduction and enhance audio system performance. The addition of such a simple component can make a night and day difference in the acoustics vehicle. By going with this simple upgrade we can essentially make riding in an 80’s Honda feel like a brand new Mercedes-Benz! The change is that dramatic!

What is Sound Treatment?

Sound Treatment, also referred to as sound deadener, comes in many forms and as mentioned before offers multiple advantages. The most commonly used form of sound deadener consists of a polymer composite of butyl-based or dense asphalt material, generally produced  with an aluminum backing. Sheets are sometimes colored or stamped with a logo, similar to the recognisable all black Ultra HushMat LIS Audio offers.

Another form of sound treatment is constructed of foam that comes with self-adhesive backing. Both types of mat vary in thickness depending on the company producing it and the difference tiers they offer independently. The most commonly treated areas of a vehicle include the doors, trunk lid, ceiling, truck bed wall, fire wall, rear storage tray, and floor pans throughout. Sound Treatment typically is used to reduce vehicle panel vibrations, thermal efficiency, and helping provide a better acoustical environment for the audio system.


What are the main benefits?

     Properly treating the inner and outer door skins of a vehicle by adding deadener to the panels greatly reduces vibration. Adding mass creates a resistance to sound passing through the metal surfaces which allows for a quieter ride due to the reduction of road noise. This also allows for more dynamic output of the mid-bass woofers in the doors, while helping with thermal efficiency of the vehicle. Keeping the cabin cooler in the summertime and warmer in the winter, putting less strain on the vehicle’s heating and cooling system. We will go on to further break down what makes each of these advantages truly beneficial to your car audio system.

The Breakdown


Door panel treatment and wave isolation…

Let’s discuss the main disadvantage surrounding sound treatment in the aftermarket mobile audio industry. The biggest downfall of adding sound treatment is just that, adding more mass to the vehicle essentially adds more weight. More weight can mean less efficient fuel economy and weaker on road handling. Another disadvantage that sound deadener has, that may not be commonly shared problem amongst other audio components, is the fact that it is typically a one time application.

Once it is installed into the vehicle it stays in the vehicle, what may be salvaged will mostly likely not properly adhere to the new surface. It is also widely debated that adding too much sound treatment to a vehicle can hinder the output gained in some SPL situations. This refers to an issue that may arise only if the vehicle is being used to achieve maximum output from the substage in a SPL competition scenario where every single decibel counts, and it typically differs from vehicle to vehicle. This isn’t a disadvantage that is commonly seen or need addressing in daily driver applications.


When treating the doors of a vehicle the main goals are to reduce panel vibrations and isolate the speaker waves. The speaker baffle (speaker mount surface) is made more rigid due to the addition of mass, this helps to keep the speaker itself from moving and allows for more accuracy and output of the mid-bass woofer. With more output comes more potential for trim panel flex, adding mat to the trim can reduce the chances of irritating rattles.

In this video you can see just how adding HushMat to the door skins can make a difference

In most vehicles, when the the door panel is removed you notice small holes and openings around the entire inner skin, which is the speaker baffle. When treating this surface it is ideal to seal these openings. This seals the front wave from the back wave creating a cabinet for the speaker and allowing for even more output and accuracy. LIS Audio always recommends sounds treatment when replacing any door speaker, whether it be a simple speaker kit or matting the entire door.

Vehicle cabin treatment and noise reduction…

When adding sound treatment to the vehicle cabin it is always best to consider the entire firewall, floor pans from front to back, and the entire ceiling. Treating these areas greatly reduces metal vibration and helps block any outside unwanted noise, which we typically refer to as “wind noise” or “road noise”, from passing through into the cabin.

If the vehicle being treated happens to be a truck, treating the rear bed wall is always recommended, seeing as how a majority of road noise in a truck comes through that back bed wall. The floor of a truck bed acts as a large speaker which reverberates road noise up to the front wall of the bed, which then passes through the rear bed wall of the cabin and into the truck. The rear bed wall can be a major inhibitor of a dynamic and full audio system as well as a quiet ride. Adding an aftermarket audio system or just wanting a quieter ride are both great reasons to add sound treatment to a truck!

The largest two surface areas of open sheet metal in most vehicles will be the roof and the floor. These areas are the most susceptible to external sounds passing through the sheet metal, via vibrations, heightening the road noise in the cabin. Treating the weak metal areas with sheets of HushMat and sandwiching foam between the carpet and metal, or headliner and metal, will help reduce most if not all rattles and external noise.

Once these two areas have been addressed the road noise will become much more quiet! In addition to killing any wanted noise covering these areas will also improve thermal efficiency in the cabin tremendously. Even more so now than before, the vehicle heating and cooling systems will require a lot less work to perform their jobs.

Killing SPL rattles and speaker reverb…

Its well known in the mobile audio industry that firing a subwoofer towards the rear of the trunk of a car will allow the wave to develop more and create a different tonality, than that of a forward facing substage. With this concept comes a ton of rattles and fixed parts becoming moving part, like rattling trim, heat shields, dashboards, or what have you. Adding sound treatment, like Ultra HushMat, to the trunk lid will decrease trunk rattles and flex greatly.

Treating the spare tire well, rear quarter panels and even the rear storage tray will eliminate any more rattles that could occur. Doing this creates a much more rigid environment for the subwoofers to play and harder surface for the subwoofers to unload off. Deadening the rear of the trunk and trunk lid together will dampen that rear wave and help the reverb to be much more accurate. After treating the entire trunk the feeling of the Sound Pressure Level (SPL) into the cabin will have a very noticeable increase!


Another place to dampen reverb is in the scenario of a full range speaker or mid-bass woofer, properly treating the area directly behind its mount surface. This helps break up the back wave causing it to dissipate more efficiently throughout the door cavity.

A quick video of an extensive HushMat installation we did in a 2017 Mazda 6 for a client

In conclusion, sound treatment is one audio upgrade that is often overlooked. Many enthusiasts don’t think of the advantages offered from treating their vehicle correctly to ensure a better signal to noise ratio in the cabin. Not every advantage of sound treatment will be truly necessary or advantageous in every application. If you have any further inquiries into your specific application involving adding sound treatment to your sound system, then feel free to contact the experts at LIS Audio better get an understanding of what is necessary to achieve your goals!

You can find more detailed information on product description at the official HushMat website found below…

Contact LIS Audio for vehicle specific information or to place an order for HushMat products…


Call: (913) 912-6990

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