Annoying Vibrations

[navylife59]

This Sticky is dedicated to those annoying rattles that occur from copious amounts of bass shaking goodness. Feel free to add to this list. Please do not post rattles and squeaks related to driving or road noise. The bigger the system, the bigger the problem so if you are rocking the optional VSE Sub, then you may not experience all of these.

1. License Plate - This is the scourge and primary source of rattles for about 99.99999% of all vehicles.
2. Junk - Believe it or not, but junk in your trunk is not always a good thing. It is time to loose the junk. Check your underdeck storage trays for any loose stuff.
3. Rear Bumper Shield Bracket Centers - What the heck is that you say. Well, they are 3 thick plastic squares that snap loosely onto the rear bumper reinforcement. The rear bumper energy absorber then fits over them but they appear to no even hold the absorber. Not too sure what they are for. They can easily be removed which will drop off only 15oz of weight. Should you choose to keep, you can run a bead of black silicon around the edges and reinstall.


4. Rear Hatch Deck Lid - The skin of the deck lid area flexes with an average system. The internal frame is only connected to the skin with a seam and spot-weld on the edges. The center area is connected via a bracket with some adhesive. This is denoted by the yellow circle area that is out of focus. If this adhesive fails, it could cause rattle. As you can see, there is plenty of opne are on the skin w/o any support. Addition of a sound-deadening material is a necessity.

5. The galvanized steel exhaust shield above the muffler is held by four 1/4" aluminum rivets. These tend to be slightly loose and can vibrate with a modest subwoofer. If you find that yours vibrates you can drill out the rivets and remove it. Alternatively, you can try wedging some pieces of material between it and the floor pan to put pressure against the rivets.
6. If you have the OEM 6" underdeck subwoofer, the plastic enclosure is not sufficiently isolated from the floor pan sheetmetal. You will have to remove it and add 1/16" or less thickness of material at the contact points. More info on the OEM sub enclosure in the next post.

[navylife59]

The OEM 6" underdeck subwoofer enclosure is affable at best. It's performance is lacking with it being almost unnoticeable once the engine is running. It does provide enough sound energy to resonate the surrounding sheetmetal but did you know that it is a source of noise itself?

First up, the material used in the enclosure is bare ABS plastic. This material is thin which allows it to flex. This allows reverberations to resonate within the enclosure. The smooth plastic interior surfaces causes out of phase reflections that muddy the bass notes.

As you can see from the photo, the opening of the tuned port for the enclosure is non symmetrical in and of varying wall thickness. As the sound wave travels through the port, portions of the sinewave (depending on frequency) begin to refract causing distortion. These variances increase in amplitude as it travels through the port. The resulting expanding irregular pressure wave creates audible noise, aka port noise. Another problem with the port is the exit's proximity to the rear bulkhead of the trunk. The pressure wave slams against the metal and reflects directly back upon itself creating more distortion and noise. With the small size of the driver, the low RMS power of the amplifier, and the enclosure is under the deck and all-weather cargo mat; the amount of audible distortion is minimal.

[excelon72]

dynamat extreme is amazing stuff or the stinger equivalent. i have a good size sub in trunk and no matter how loud i turn it up neither the license plate nor the rear deck rattles at all.... im installing a back up camera will post pics on the dynamat job...

[navylife59]

A low buck deal that has always worked well on large, open surfaces it the 1/2" foam panel board with the aluminum facing. 3M spray glue (hi-temp for overheads) and a zig-zag of Liquid Nails adhesive does the job of holding it in place on the foil side. Does wonders for blocking the heat in headliners, cuts down on sound reflectivity, blocks road noise, and does a fair job of deadening the panel. The Dyno-mat type stuff is great for deadening a panel but sucks at everything else.

For my doors where space is a premium and you need something that can handle getting wet, I use that cheap automotive carpet that you can buy at autoparts stores and Wally World. A good 3M adhesive spray does the job holding it up. It cuts road noise and reflectivity close to the that of the foam board but does not deaden the panel. You will need to add some of the Dyno-mat stuff there. The carpet takes up less than 1/8" space. It will make the doors quieter (road noise), adds way less than a pound of weight (per door), and will sweeten up those door speakers when the windows are up.

[Prometheus]

I have also found that the head liner in the back towards the hatch tends to rattle on occasion when I'm really getting with it because there is a fair amount of open space back there between it and the actual metal.

[Prometheus]

@ excelon72 What Kenwood Excelon do you have?