25 replies to this topic

[AlexHillTVR]

As much as I like the sound of the engine right behind my ears I'd like to try and add a bit of refinement to the car as it is a daily driver. I like exhaust noise, heard out the windows mainly, not so much the mechanical noises heard transmitted to the cabin. Now I know a bit about sound isolation and I know the best way to isolate a noise source is with a sealed air gap between the two (like double glazing) stuffed with absorbing material like Rockwool. But the problem I am getting is that there is a lot of high frequency engine noise being transmitted to the cabin. Therefore as high frequencies are easily diffracted due to their shorter wavelengths, something in the way (such as added sound-proofing material) might work to reduce that. I'm thinking that the parcel shelf needs to be more dense and is generally just sh*t at sealing with the bulkhead. Has anybody had a go at doing this and had any good results? I'm not too bothered about adding a bit of weight, I weigh 55kgs so can afford 10-20 kgs without becoming slower than the next man! haha

[turboluca]

Try a Fred666 carpet for hour inside that will help .

[mbes2]

Sell it and buy a normal daily car.. Or keep vx for weekend fun toy

[techieboy]

You bought the wrong car. Buy a Boxster.

 

You can build a double layer brick wall behind your seat but it'll make next to fcuk all difference given the construction of the car and the fact it's open topped (and also has a shitty inline 4 engine that's hardly a paragon of smoothness).

[pete-r]

Couple of easy things, if you have a hard top take it off. My hard top trapped noise and it was much quieter without, and even quieter with the roof off completely. You can put Dynamat onto the panels but it's not cheap and may not get rid of everything. On my old Corrado I did a Hifi install and put little bits of dynamat on joins, panel touches etc and it made a huge difference but that was because the car suffered more from rattles on bumps than general noise. The recommended way is to cut it up into fish finger shapes and stick together in a lattice # pattern, say on the inner door skin and dash or behind seats. If you sheet dynamat your wasting money. You can also check your windows and roof fit well in case your getting wind coming through. Apart from that there's not much you can do other than crank the stereo lol.

[AlexHillTVR]

As much as I appreciate the "you bought the wrong car" comments, the ones with constructive opinions are slightly more helpful I spose that's an issue for me at the moment Pete because I don't have the key card for my Blaupunkt! :haha:

[robin]

earplugs

[fezzasus]

As much as I appreciate the "you bought the wrong car" comments, the ones with constructive opinions are slightly more helpful I spose that's an issue for me at the moment Pete because I don't have the key card for my Blaupunkt! :haha:

 

It's true though.

 

You can weigh it down with 50 kg of dynamat to try and improve things, but it'll still be sh*t compared to a normal car. I went down that road, still had a car that leaked and locks that froze. Replacing the exhaust and air filter made things better, but it left the car without any character. The real solution was to use a different car as my daily, then you can really enjoy the VX for what it is.

[Mr Apex]

Disagree with all of the "you bought the wrong car" rubbish. I love my VX, it isn't my daily drive, but it definitely could benefit from reduced mechanical noise from the engine bay. Most of us have increased the induction noise and the SC conversion adds an extra belt, which makes some additional noise just behind the driver. Improving the bulkhead sound insulation would add to the enjoyment of the car - as does eliminating knocks and rattles. It'll never be a BMW, but it doesn't have to be a Fiat... any interesting thoughts on how best to achieve better sound insulation would be great.....

[Wolfstone]

It's a very mechanical car and personally I enjoy it partly because of that. Enjoy it for what it is.

[Rosssco]

But fundamentally, the only thing that separates you from the engine back is a couple bits of fibreglass / plastic, and some sh*t sound deadening material. You can dampen vibrations down a bit and make the car "feel" a bit more solid with some sound deadening materials, but you won't change the fundamentals of the car. Go try the current range of Lotus with pretty much the same chassis / set-up and you'll find them the same.. As above, buy a boxster or Mk3 MR2..

[Mr Apex]

Tell that to everyone who has

 - changed the wheels

 - tuned

 - painted

 - upgraded suspension

 - added carpet

 - improved the lights

 - changed the seats

 - etc etc etc

Improved sound proofing is just as relevant. Not for everyone, but.... hardly anyone just enjoys the car for what it is. The OP is looking for ideas or experience in the area of soundproofing. I'm interested, because I also want to reduce mechanical noise in the cabin. I'm not particularly interested in the comments which suggest that the concept lacks value. Suggest that the OP isn't either....

[AlexHillTVR]

Tell that to everyone who has  - changed the wheels  - tuned  - painted  - upgraded suspension  - added carpet  - improved the lights  - changed the seats  - etc etc etc Improved sound proofing is just as relevant. Not for everyone, but.... hardly anyone just enjoys the car for what it is. The OP is looking for ideas or experience in the area of soundproofing. I'm interested, because I also want to reduce mechanical noise in the cabin. I'm not particularly interested in the comments which suggest that the concept lacks value. Suggest that the OP isn't either....

Thank you Apex, exactly what I was thinking! Sound absorbing materials foam materials can typically only reduce noise from a source by up to 9dB, after that, it's a lot more about isolating the two acoustic spaces- the engine bay and the cabin.

[Zuber]

I still don't get why you would go to do much trouble when you could simply use earplugs. You can get fancy reusable ones that take out high pitch noise and allow conversation for example.

Edited by Zuber, 31 May 2015 - 11:02 AM.

[Mr Apex]

I have friends who sit in the passenger seat. I like to be able to hear them scream.

[Mr Apex]

I don't know much about sound insulation and isolation, but I think that there is probably opportunity to reduce general cabin noise by sorting out the panel resonance? The floor panels under the seats and the bulkead panel all vibrate, Presumably a relatively thin layer of some type of sound deadening material would reduce the noise generated by the vibration?

[techieboy]

I have friends who sit in the passenger seat. I like to be able to hear them scream.

 

You can, the earplugs only attenuate noise, they don't stop it. You can happily hold a conversation whilst knocking off a chosen level of volume.

[slindborg]

I wore ear plugs and the radio wasn't set to silly levels to hear it. Tbh the noises (not levels) are part of the fun and he point of the car

[techieboy]

I don't know much about sound insulation and isolation, but I think that there is probably opportunity to reduce general cabin noise by sorting out the panel resonance? The floor panels under the seats and the bulkead panel all vibrate, Presumably a relatively thin layer of some type of sound deadening material would reduce the noise generated by the vibration?

 

Okay. My car has a Dynamat/bitumen type noise and vibration absorbing/damping material applied to the rear bulkhead (behind the parcel shelf) also to the both the upper and passenger compartment facing "box" that the petrol tank resides in and also on the floorpan underneath the seats. It also has a thick dense noise absorbing foam sheet in the void between the parcel shelf and the bulkhead. It makes no appreciable difference to the noise levels in the car (when compared with other VX's I've driven or passengered in). Build the Berlin Wall behind the seats but there is no hiding the fact you've got a thrashy 4-cylinder aluminium engine 6" behind your head and 90% of the sound doesn't come through the bulkhead anyway.

 

Do whatever you want but the fact is, if NVH is an issue for you, nothing will make a significant improvement given the construction of the car. A Boxster/Z4/whatever, where NVH is a design concern for the manufacturer is the real answer. Or just drive around at <2,000rpm.

[Mr Apex]

I agree that the noises are part of the fun of the car - the levels can be a problem, though. There are certain frequencies that just aren't pleasant. I hate wearing ear plugs - after a while, they ache, you always have to wash them etc etc. There is a bulkhead behind the driver - in the tubby, I believe that they added some sound deadening, the NA has none. I'm guessing that the tubby sound deadening made a difference, or they wouldn't have bothered. So adding the tubby sound deadening to my car would probably be a useful mod. There might be better, more effective materials available than those used by Vauxhall, too.