Low frequency 'boom' in cabin

[guitarman001]

Damn, that's almost disappointing to hear...

I wonder what it is, grrr... 

 

If I can pad mine more in the right places I'd still like to keep it. It's been ok on today's drive with blankets in the boot - almost a pleasure. Will check it during next week's drive, though the longer I leave this, the less I'll get for it in trade. 

[guitarman001]

Note to self - silent coat is fairly cheap on Amazon. £40 for 30 sheets.

 

-- is it easy to remove body panels to fit these? Or is that something a garage would have to do? 

[Petunet]

Fairly simple to remove the panels, there is a PDF manual for interior somewhere here.

 

[guitarman001]

If that's the case then for the sake of £40 I'd be willing to try that.

[guitarman001]

 

-- if anybody has the link to hand... Appreciated..! 

 

The car really is great other than this issue, though today with the blankets in the back, it's been ok for 95% of the time. It looks stunning in corrida red, too... And handles better than the A3's I tried. I saw a red 2016 vrs in front of me today and man, that looked amazing... Better than equivalent Audi's, to be honest.

[guitarman001]

Annoyingly I could hear it a bit coming back, maybe for 15% of the time. Teeth hurt a little and ear a tad. I actually wonder if this is bad for hearing, long-term... I'm being serious!

 

When I go over a bump, there's next to no noise when the front wheels go over. It's when the back wheels go over. 

 

If I could get an A3 for £13k I'd probably make the trade. Grudgingly.

[guitarman001]

https://dynamat.eduardomaio.net/citroen-c6/deadening-the-boot/

[guitarman001]

Just rode in my dad's 1.2 TSi rapid. I could hear the same noise but a lot less. No real "reverberation".

 

Then drove mine over the same road and we could both hear it. More reverberation hitting the ears.

Edited 24 April, 2017 by guitarman001

[Alpha2110]

Dont think sound proofing is going to fix this, there is a thread on here and a few people have done it and it dosent get rid of the problem. The frequency is to low at 220hz. I think it may help with the higher frequency but saying this i have noticed very little difference. However take the 220 with a pinch of salt, it was found using a tone generator, realy you need decent vibration sensor so you can look at all the harmonics. 

 

I would like to know what the differences are between the octavia and the superb,  as the mk2 superb rides and sounds far better, and even drives better.

[guitarman001]

I can get an A3 for total extra £3400 plus £500 loss on Skoda... Hmm..

[guitarman001]

I do have a very expensive spectrum analyser at work but there's zero chance getting that in the car!

 

Also rode with 3 separate friends yesterday who could all hear it but all said they'd keep it. IMO it's been than my friend's A4 allroad - the spec is so good. Clearly I can't make my mind up!

[guitarman001]

Does the superb have this same issue?

[Srejber]

1 hour ago, guitarman001 said:

I do have a very expensive spectrum analyser at work but there's zero chance getting that in the car!

 

Also rode with 3 separate friends yesterday who could all hear it but all said they'd keep it. IMO it's been than my friend's A4 allroad - the spec is so good. Clearly I can't make my mind up!

I tried to make some noise with use of "toy" app for my iphone. A simple tone generator. iphone plugged into AUX in, so i was able to play with various frequencies through speakers in my car. i found that 36Hz is THE NOISE.  so i simulated the resonance perfectly.

 

it must be 36 Hz or higher harmonic...

[guitarman001]

That's a great way to do it, assuming it's accurate enough. Hmmm, nice one!! 

 

I'll need to find an equivalent android app

[guitarman001]

Ok mine shows a peak at 65Hz but don't think the mic on the phone is that good. Could even try using my portable recorder (a good one) to record some audio then post-analyse the waveform. I'll do that..

[Srejber]

23 minutes ago, guitarman001 said:

Ok mine shows a peak at 65Hz but don't think the mic on the phone is that good. Could even try using my portable recorder (a good one) to record some audio then post-analyse the waveform. I'll do that..

Yes  your 65Hz is close to the higher harmonic for my 36Hz. We can´t speak about accuracy of single Hertz, this is a job for pros...

in my case, 36Hz tone generated in my Iphone, played trhough AUX-in/infotainment system/speakers  hurted my ears the most. but it is very personal to all of us - the peak-paint-point :-)

 

This frequency is so low and loud, it must be generated by movement of some big enough flat object, which compresses the air in cabin. easiest way to imitate this painfull sound is to slap bootlid with slightly more power. just ask some friend to slap the fifth door while you seat in the car. your head  explode then :-)  on the other site, when driving with fifth door ajar, it almost disappears. for me, clear evidence of  the problem with the fifth door. 

 

 

i am going to remove the plastic trim, (only one TORX screw under the handle and "peel" it off) when the weather improve.

 

 

 

[guitarman001]

Have you performed this experiment in a similar car (Audi A3, Seat Leon, VW Golf)? 

If there was flat out another car for decent money I'd trade but it's going to be expensive for another, with no clear winner. 

[WillM82]

 

I removed the rearmost plastic trim, as I thought it was maybe resonating against the glass. Had no effect.

7 minutes ago, guitarman001 said:

 

Have you performed this experiment in a similar car (Audi A3, Seat Leon, VW Golf)? 

If there was flat out another car for decent money I'd trade but it's going to be expensive for another, with no clear winner. 

 

 

We have a 2010 Leon in the household, there is a small amount of noise from the bootlid, and the exhaust is a little raspier (sportier?) but compared to the Octavia there is nowhere near the same amount of vibration / buffeting.

 

Unfortunately I don't currently have audio resonance equipment to scientifically measure the difference.

Edited 25 April, 2017 by WillM82

[guitarman001]

So is this the thin plastic trim around the edge of the boot lid that you removed? Just so we're on the same page...

 

What is the Leon like compared to the skoda, other than the noise?

[WXSKODA]

Hi,

 

I posted a lot on this in 2015 and eventually had adjustments made to the stops in the boot which did in fact help somewhat!

 

However, I've just noticed the face lifted model has new spring loaded stops and so I asked the dealer if they can be fitted to the 2015 model but I got a quick "NO" (I also asked for a test drive but got another "NO" as they don't yet have a demo car!) so I'm wondering if anyone has any proper info on these new spring loaded ones?

[WillM82]

I've adjusted mine til I'm blue in the face, doesn't make that much difference to the vibration.

 

I did read about spring stoppers on Scirrocos, but no definite answer if they could be retrofitted to prefacelift Octys.

[WillM82]

38 minutes ago, guitarman001 said:

So is this the thin plastic trim around the edge of the boot lid that you removed? Just so we're on the same page...

 

What is the Leon like compared to the skoda, other than the noise?

 

This panel.

 

The Leon feels more like a hot hatch, it is a 1.4 petrol Vs the Octavia 1.6 diesel DSG. Octavia a bit of a bigger car. They're similar but feel almost like a Focus V Mondeo.

[guitarman001]

What stop adjustments are you talking about?

Simply loosening them?

 

Thanks for the pics, those are the panels I was talking about earlier. Shame it's had no effect but thanks for trying

[WXSKODA]

When boot is up there are two stops on it, one on the left and one on the right about half way up! and then on the frame where these sit adjustment can be made.

[WillM82]

I think it was this page that described the Scirocco bootlid stoppers

 

http://www.sciroccocentral.co.uk/forum/viewtopic.php?f=25&t=1884

 

And this page describes a similar issue on a Porsche Cayman

 

http://www.6speedonline.com/forums/boxster-cayman/284054-solution-cayman-cabin-buffeting-pressure-modulation-sonic-boom-problem.html

 

I tried felt patches, as you can see from the above image some felt circles, but made no difference.

 

Interesting that they all seem to be VW group hatchbacks

Edited 25 April, 2017 by WillM82