Having spent a lot of time (and money), trying to reduce the road noise in my Fabia vRS & only seeing minimal improvement, I was wondering whether an active electronic noise reduction system would work?

What I had in mind was the electronic circuitry of Bose QC 25 noise cancelling headphones. I'm thinking that microphones taped to the wheel arches & then fed into the input of the Bose QC's, the output then amplified & driving a couple of speakers (existing ones preferably). 

I am familiar with the operation of electronic active noise cancellation, but I do not know whether my proposed system would work?

 

Any sound/electronic boffins care to comment?

The main noise paths from the tyres into the bodyshell and hence the passenger compartment tend to be through the suspension components, so the frequencies will change from wheelarch to where you hear them.

 

Also, the electronics of noise-cancelling systems don't tend to be designed for having 70mph water jets fired at them for sometimes hours at a time.

 

Have you thought about using "cooking model" suspension bushes in the hope that they're softer than the vRS ones?

If you're trying to cancel the noise heard in the cabin, the microphone(s) need(s) to be in the cabin too, no? Gotta sample exactly that which you wish to cancel.

 

Edit:  hmmm, or is there a logical flaw there? If it worked, there'd be nothing to sample, in order to cancel...? :think: 

The main noise paths from the tyres into the bodyshell and hence the passenger compartment tend to be through the suspension components, so the frequencies will change from wheelarch to where you hear them.

 

Also, the electronics of noise-cancelling systems don't tend to be designed for having 70mph water jets fired at them for sometimes hours at a time.

 

Have you thought about using "cooking model" suspension bushes in the hope that they're softer than the vRS ones?

 

 

If you're trying to cancel the noise heard in the cabin, the microphone(s) need(s) to be in the cabin too, no? Gotta sample exactly that which you wish to cancel.

 

Edit:  hmmm, or is there a logical flaw there? If it worked, there'd be nothing to sample, in order to cancel...? :think: 

 By way of experiment, this is what I have done.

 

I recorded the inside cabin noise using my mobile phone,  as an .mp3 file & played it back through my hi fi system at home, at a volume level that approximates that in the car. As soon as I switched on the Bose QC's, the effect was dramatic. Almost silence! One drawback though,-  if I had music on in the car it also had a severe effect on that as well. It didn't eliminate the music entirely, but it altered it nearly out of recognition.

That is why I suggested locating the microphones outside of the cabin so that they do not pick up the inside sounds - and thereby modify the music as well.

The main purpose for the sound proofing is so that I can enjoy music on the move. Not easy to do with present noise levels.

I suppose my next move is to remove the electronics from the Bose & hook up a real situation, but I don't want to ruin a marvellous set of headphones, but if I thought I was in with half a chance I'd risk it.

I'm presuming that you've done the usual things like changing tyres, and fitting sound deadening mat to the bonnet and and bulkhead. If so, then I honestly think that your other path, bearing in mind that noise in the engine bay and wheel arches is audibly different to that in the cabin, has to be changing the suspension bushes. As you say, any attempt to use normal noise-cancelling technologies with pickups in the cabin will detect music (and conversation) as well as "car noise".

Could you not, you know, just wear the headphones in the car and then you'll only hear music?  :|

Couple of pointers-

Mercedes put the microphones in the headlining for the noise cancelling system in the S Class.

Reading the following article, they say the bandwidth they use for car noise cancellation is much narrower than used in headphones & therefore wouldn't work.

http://articles.sae.org/12747/

Bose do noise cancellation systems for cars, so may not be too difficult to retrofit. Costs may be expensive though

Couple of pointers-

Mercedes put the microphones in the headlining for the noise cancelling system in the S Class.

Reading the following article, they say the bandwidth they use for car noise cancellation is much narrower than used in headphones & therefore wouldn't work.

http://articles.sae.org/12747/

Bose do noise cancellation systems for cars, so may not be too difficult to retrofit. Costs may be expensive though

That's general, but all the statements are actually correct. Of particular note is that with narrow-frequency cancellation you will have to tune the cancellation frequency spectrum to the vehicle (make, model and shell style), trim level (higher spec cars often have more sound deadening as standard) and engine.

Could you not, you know, just wear the headphones in the car and then you'll only hear music?  :|

 

Works fine if you are travelling alone, although it does make you oblivious to outside danger signals eg, honking horns etc, also you feel kind of isolated. Also not sure of legal status & safety issues of wearing headphones.

 

I'm presuming that you've done the usual things like changing tyres, and fitting sound deadening mat to the bonnet and and bulkhead. If so, then I honestly think that your other path, bearing in mind that noise in the engine bay and wheel arches is audibly different to that in the cabin, has to be changing the suspension bushes. As you say, any attempt to use normal noise-cancelling technologies with pickups in the cabin will detect music (and conversation) as well as "car noise".

 

I've installed Dynamat in rear boot floor, wheel arches, door panels, & floorpan. Hard work for not much improvement. Haven't changed tyres & loathe to do so whilst plenty of tread left, & how do you choose replacements? Suspension bushes? Hadn't really crossed my mind as a major contributor to noise, but something I may consider.

One thing i can say, is that tyres makes a massive difference to noise. When i had my hatchback, i swapped my vredestein sessanta tyres for toyo t1r ones and it was ridiculous how loud it was. So although you dont want to change just yet, maybe looking at the db rating for the tyres your buying. Also the bushes should make quite a difference if they are softer. I believe the noise in the fabia is down to the general money saving efforts of skoda. Its more of a vibration noise than road noise.

Works fine if you are travelling alone, although it does make you oblivious to outside danger signals eg, honking horns etc, also you feel kind of isolated. Also not sure of legal status & safety issues of wearing headphones.

 

 

I've installed Dynamat in rear boot floor, wheel arches, door panels, & floorpan. Hard work for not much improvement. Haven't changed tyres & loathe to do so whilst plenty of tread left, & how do you choose replacements? Suspension bushes? Hadn't really crossed my mind as a major contributor to noise, but something I may consider.

After a quick Google, I think Dynamat is about as good as it gets for mass insulation and resonance changing (frequency raising and amplitude reducing) techniques. (I was checking that it is adhesive and not just sit in.)

 

I'm serious about suspension bushes; more road noise is transmitted through the suspension to the cabin than travels through the air. If there's more than one spec for Furbie 2s, I'd expect the vRS to use the hardest and hence most noise-transmitting spec.

 

One thing i can say, is that tyres makes a massive difference to noise. When i had my hatchback, i swapped my vredestein sessanta tyres for toyo t1r ones and it was ridiculous how loud it was. So although you dont want to change just yet, maybe looking at the db rating for the tyres your buying. Also the bushes should make quite a difference if they are softer. I believe the noise in the fabia is down to the general money saving efforts of skoda. Its more of a vibration noise than road noise.

With the note that I drive an Octy, not a Furbie, I'd disagree about the Toyo T1-R being noiser than an asymmetric multiblock (general case; no specific experience of Sessantas).

That said, I agree about looking at the dB rating of new tyres, although the quoted figure is "drive-by noise", not in-car.

Also, reducing vibration noise was where the Dynamat came in. 

Maybe it's worth giving these guys a call http://www.deadening.co.uk/

 

They maybe able to advise you or point you in the right direction. Not sure how much noise is generated in your car, I have done a little bit of deadening to mine and can't say I hear too much road noise when I turn my system up I like to listen to music at quite high volumes and even with the window open I can still hear my music quite clearly.

Loads comes in through resonance from the boot floor and spare wheel well, so have you dound deadened that with something like dynamat and then put down some underlay like cloud 9 or something below the carpet.

 

In terms of the suspension is it OEM or otherwise?