Road Rage

As a mechanical and electrical engineer, I have a slightly different perspective on mechanical vibration and sound. Cars have a resonant frequency, like any mechanical device, and the lower in Hz it is, the stiffer the body structure. Advances in CAD and FEM (finite element analysis) first enabled by Cray supercomputers have allowed engineers to greatly reduce true rattles - what most of you are describing is the vibrational noise caused by minor sub-structures in the car - such as the rear shelf, and the center stack spring-loaded doors.

These noises are primarily affected by temperature and road surface. The various plastics, rubber, and metal parts all shrink and swell in response to lowered and raised temperatures, each to its own structure. One will find that when the car is first driven, there are certain interior noises - or when the interior has been sitting in the hot sun all day, noises will ebb and flow.

There is also truth that some noises will go away - this is the result of either the surfaces abrading against each other until they either no longer resonate against one another, or have been worn smooth enough that the "slip-stick" phenomenon which causes many squeaks and buzzes goes away.

Then there is terminology - engineers and audio guys are very specific in the language they use to describe sounds. What some here call a rattle, is merely a buzz. True rattles generally are defined as metal to metal noises - they were common in domestic vehicles in the 70's, when sloppy assembly and union power each was at its zenith. Plus, the advances in simulation of structural sub-assemblies have allowed even first-year cars like ours to come out pretty damn well.

I am sometimes bothered by them, but the basic structural integrity of the TL is fine, and after one year and 4 seasons, I may go after any residual noises on my own.

Check out the various felts available as www.mcmaster.com. Some are available as dots with adhesive, or various thicknesses and densities, some with adhesive backing - they work great to control NVH. Larger surfaces can be custom cut, and then a contact adhesive like 3M 77 may be used to adhere them.

Bonedoc

Hey Road Rage,

never mind my PM, I found it. Thanks!

Road Rage

The 2nd sentence should state the lower in frequency the less stiff it is. Resonant freqs increase as stiffness increases - cars used to be in the low 20's, and are in the high 30 range now. Thx to fredo0709 for catching my dyslexic statement - when I type fast, I sometimes reverse my thoughts.