I'm toying with the idea of sound treatment

GTE · 19-12-2010 11:50pm #1

Hello all,

There is a rattle coming from under the dash which I am very sure I caused last Summer when I had the glove box out and after refitting was left with 3 screws :rolleyes::o:p:(:pac:

So, during the Summer when things should be quiet I plan on doing my best on sorting it out.

This will mean taking the glove box out so I was thinking about putting some sound treatment along the firewall and doing what I can in the boot area too.

One thing I have noticed over the past few months is that the car does have a lot of wind and road noise when cruising. I know I will have the car for a few more years. There is no way I am going to scrap it while it still moves so I dont mind doing the odd project on it from time to time.

My plan is to take a recording and finding out where most of the noise is coming from frequency wise and then seeing what kind of treatment I would need to get rid of that general area of the spectrum. No point doing really thin foam when its all mid freq junk getting spewed out.

I can imagine a lot of the noise will be glass related so I will have to do some more thinking about it.

Another aspect as that some of the noise is going to be coming through the chassis from the wheels so whether its going to be worth while doing treatment in only parts is a consideration.

Just wondering what all the project do-ers think of it.

If I put it in I should be able to whack it out if I scrap the lovely wagon. Doesn't bare thinking about

Mr.David · 20-12-2010 9:26am

I think I can help......I'm a wind noise engineer

Well, one useful tool for you would be a stethoscope - you can use this to locate directional leakage for instance along the door margin seals or the glass run seals.

To be honest, typically about 30-40% of wind noise is generated by the underfloor (and often difficult to seperate from road noise). You could try making some new undertray panels that were nice and flat and fixing them on.

Other than that, as you said the glass is key. A lot of noise is generated by the overall form of the vehicle - and features such as the a post and wing mirrors. It is possible to get acoustically laminated glass which makes a big difference but I have no idea about getting it made as a 'one off'.

One key thing to remember is - there is a huge masking effect. So, if one area of the vehicle is really poor/dominant e.g. transmission through the glasshouse then there is no point soundproofing another area - the benefit can be lost and masked by the dominant area.

Its quite a difficult challenge! I'd start with the stethoscope (someone else driving you in the passenger seat!) and see if you can locate any leakage. Fix any crappy seals.

20-12-2010 11:04am

I'd lubricate all of the door rubbers etc as a starting point to ensure a good seal from them. Will help with wind noise anyway.

GTE · 20-12-2010 2:22pm

Mr.David wrote: »

I think I can help......I'm a wind noise engineer

Well, one useful tool for you would be a stethoscope - you can use this to locate directional leakage for instance along the door margin seals or the glass run seals.

To be honest, typically about 30-40% of wind noise is generated by the underfloor (and often difficult to seperate from road noise). You could try making some new undertray panels that were nice and flat and fixing them on.

Other than that, as you said the glass is key. A lot of noise is generated by the overall form of the vehicle - and features such as the a post and wing mirrors. It is possible to get acoustically laminated glass which makes a big difference but I have no idea about getting it made as a 'one off'.

One key thing to remember is - there is a huge masking effect. So, if one area of the vehicle is really poor/dominant e.g. transmission through the glasshouse then there is no point soundproofing another area - the benefit can be lost and masked by the dominant area.

Its quite a difficult challenge! I'd start with the stethoscope (someone else driving you in the passenger seat!) and see if you can locate any leakage. Fix any crappy seals.

Thanks muchly.
I have a little handheld recorder or even a little interface that I can connect to my laptop and hook up a small diaphragm condenser. Reasonably directional and ruddy sensitive. I may try that to find some leakage since I have them to hand.

I never thought of the seals actually. Would a light coating of a silicone lubricant be suitable?

This is what a user of ukmkiv forums did to his doors.

He took the door cards off then the door skin and applied what seems to be a sort of rubber damper to the inside of the outer skin of the car.

I wouldnt be too keen to taking the inner skin out but I would be up for applying some dampening to the inner skin which is just thin aluminium.
Along with that I could fit a layer or two of foam to the inside of the door card.

He said that it didnt do a whole lot but it did tighten up the transient response of the speakers. Not to bothered with that.

Ill do some more research!

Thanks all!

A recording will reveal all!

20-12-2010 3:11pm

bbk wrote: »

I never thought of the seals actually. Would a light coating of a silicone lubricant be suitable?

Dunno what the main ingredient in rubber and nylon lubricant it but that's what I would recommend you use.

GTE · 10-08-2011 1:37pm

http://www.youtube.com/watch?v=I5E9mjI3y1E

This cropped up in my mind again.

Seems very good. The camera can not detect the differences in sound because at 100 to 300 Hz the microphone would not be great but the screen grabs to show about a 10dB drop in that area.

Does anyone know of anywhere in the UK or Ireland that sells these products at a good price?

I'm gonna go out now and take a recording of the car with a decent mic.

This is the freq response of the mic just so I dont lose it, it will interesting to see where my problems lay.

http://www.zoom.co.jp/english/products/h1/h1_16.jpg

GTE · 10-08-2011 2:41pm

So, my test with a different mic, a SE Electronics SE2200a for anyone who knows it yielded the attached results. The mic was pointing towards the front of the car and pointing it towards the passenger and drivers windows from my position and center had more or less the same results.

Now I don't have an SPL meter so the reading isn't giving the actual volume but it does show that there is a lot more low end going on in the wagon compared to the rest.

Perhaps these products could do a good job for me.

Freq response of the mic.
http://www.seelectronics.com/images/sE2200a_chart.jpg

10-08-2011 4:13pm

Get yourself some dynamat extreme sound deadening and place it where you think the noise is coming from. Its great stuff but it was never cheap to buy here, buying online or in the north would probably be cheaper

Quazzie · 10-08-2011 4:14pm

Mr.David wrote: »

I think I can help......I'm a wind noise engineer

That sounds like the most made up job title ever.

I'm toying with the idea of sound treatment

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