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Where does the flapping noise come from?

Ray De Man

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Ok guys I have this very annoying sound coming from the rear-end, somewhere near the petrol tank and bumper bar. It only makes this flapping noise when the subs hit very low notes. Yes everything else vibrates but this is the most annoying.

Car has been sound deadened on the rear shelf and boot lid. Where is the place should I S/D now and any ideas where the flapping noise is or what's flapping? :thumbsup:

Oh instead of making another thread, is there a solution to stop my windscreen from popping out from the top? I guess this is due to the roof vibrating the windscreen out of place. This has happened approx 3 times already and is getting to be a pain as have to call someone to refit it. :bang:

Cheers in advance :D
 

Ray De Man

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No I don't think its that, it's much lower. From outside the car standing at the back, it looks like it's coming behind the bumper but it could be the boot floor. Any ideas???
 

camstatic

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Those pesky air filters that are in the boot behind the bumper! My system has torn those to pieces and they flap around like crazy and make one hell of a noise. Cut out paper element and replace with air filter foam. :)
 

Ray De Man

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How do I get to them? I guess there is one on either side?
 

camstatic

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Not sure on the VX, just pull out the spare tyre and they're right behind it on the VP. A quick lift of the boot carpet should reveal 'em.
 

Ray De Man

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Cheers Camstatic, i'll have a look later.

Any ideas on my windscreen problem?
 

camstatic

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Too much flex! There isn't really much you can do, you could try sound deadening the hell out of the roof inside the hood-lining, but it'd be expensive and time consuming... If you could deaden the roof enough to get its resonant frequency below say... 20Hz, you might have a better chance of keeping the glass where it is.

Explanations of resonant frequency can be found all over the web, but the general gist of it is: The more something weighs, the lower resonant frequency it has. Sound deadener works by making panels in your car heavier, in turn lowering their resonant frequencies to (hopefully) lower than the car stereo emits, stopping vibrations and rattles. You can even tape up door lock linkages and things, making them heavier to lower their Rf.
 

holdenboy

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strengthening the roof (in between the bracing ribs) will minimise the flex in the roof and therefore the top of the windscreen. You can do this by either sound deadening the sheet metal or glueing like 6mm MDF to it.
 
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