Kill The Noise - DSport Magazine
"Hey, do you want to hear the most annoying sound in the world?," Try cruising in a 1000-horsepower Supra in sixth gear at 2,500 RPM with the 5-inch exhaust system in the constant drone mode. That's pretty damn annoying. Our 2005 Dodge Ram 3500 with Cummins 5.9-liter Diesel is a close second thanks to its 5-inch exhaust and big truck tires. Of course, the obvious solution to unwanted noise is to simply turn up the radio. However before installing a 1000-watt sound system to drown out the road noise, we decided to see if we could have any luck in reducing the in-cab noise levels.
BETTER OFF DEAD
Sound deadener or dampening materials have been around since the late 80s. Originally used in high-end car audio setups, these types of products can be effective in eliminating squeaks, rattles and unwanted engine, exhaust and tire noise. These products work by essentially not allowing the metal that they are attached to vibrate or resonate at audible frequencies. As a benefit the sounds created within the cab are amplified, so conversation or car audio sound levels are improved.
We decided to see if we could record a difference in interior noise by using three sets of ears along with a Radio Shack 33-2055 Sound Level Meter. With the meter set to slow response and C-weighting, we would record the sound levels from the center of the cab at idle, at 45MPH on throttle, at 45MPH coasting, at 80MPH on throttle and 80MPH coasting. During the baseline test Jeren Walker, Brian English and Vinh Nguyen commented that the truck was all intensive purposes pretty dang loud in the cabin. The vehicle exhibited an increse in noise with increased speeds (mostly due to tire noise) and to increased noise with throttle input.
The hardest part of the install was the removal of the factory interior. While normally an easy affair, Dodge decided to use tamper-proof TORX bit driven fastener throughout the cabin. With the interior removed, installation of the Boom Mat was a snap. Cut, peel, stick. Since the material is very flexible, it could be put over most surfaces with little cutting needed. The adhesive proved strong enough to adhere overhead without issue. The entire cabin was covered in Boom Mat and the tester and equipment hit the same street of road for testing.
According to all three sets of ears, the Boom Mat made a dramatic difference to the in-cabin noise levels. Jeren, Brian and Vinh formed a consensus opinion that the Boom Mat reduced the noise at idle, at speed and at cruise. Surprisingly, the Radio Shack meter wasn't in full agreement. At idle, the meter did not record a single difference. Off-throttle speed testing, showed some improvement, while the on-throttle results showed a -3dB reduction in noise levels. A -3dB reduction equates to a 50% reduction in sound energy. Since our brain and ears perceive sound levels in a different fashion, a -3dB drop in noise will sound about 20% quieter.