I was at a loose end on Saturday after breakfast (about 2pm) so I started on this!
After two hours, I had a garage full of seats and panels, and a 500 that looked like this... (see pics below)
It's clear that the team charged with soundproofing for the 500 Sport were operating on a tight budget. After all, when you have to fit two pretensioners to the seatbelts (one on the reel, one on the lower mounting), side impact G-sensors, curtain airbags, and rear seat ISOfix mountings, there can't be much money left for deadening pads.
What was a real surprise, though, was that it appears that somewhere along the line, a golden rule of soundproofing was ignored The materials that are there can't work properly because other materials are missing - I'll explain in a moment.
Now I can't claim to be a qualified sound expert (uni physics is ten years ago for me and it was mostly about electricity and light), but I have years of experience taking apart cars like Alfa 164s and 166s which have a *lot* of soundproofing that I've studied and removed. For example, I've compared the later 166 with "improved sound deadening package" against the earlier version, to see which areas were improved (the deadening pad under the rear seat has a foil layer, for example, and the felt on top of that has a layer of bitumen where the earlier version does not...) The manufacturers have many tools for measuring and modelling that we do not have, so it makes sense to see where they decided to make improvements when the purse strings were loosened. Who would have thought that noise came from under the rear seat...
And of course, I've read lots of pages about the subject. There is a clear difference between how soundproofing is applied in the aftermarket (typically to hot-rods and other bare-metal restorations) and how the OEMs do it. The sellers usually want to sell more of their product, but I think a good example of fairly-unbiased (!) advice is http://www.sounddeadenershowdown.com/cgi-bin/index.cgi
In the aftermarket, you generally see everything covered wall-to-wall with Dynamat or a similar damping layer, which has a foil top surface. Some people leave it at that, but the better people go on to add a layer of 'fluff' (recycled cotton felt/underlay) - as our own pierce_jj shows in his excellent guide.
Incidentally I'm not out to disprove what pierce_jj has (successfully) achieved and shared - I found it inspiring - I only want to add a little more of my own thoughts and methods as my project progresses.
The golden rule of successful sound deadening seems to be to make a 'sandwich':
1- Damping pads on sheet metal to control resonance (ringing like a bell is stopped by 25%-50% coverage, no need to go wall-to-wall)
2- What I call the "fluff" - or foam - a soft layer that dissipates higher-frequency sound energy
and then:
3- constraining layer - a relatively thin but heavy surface that traps the sound in the soft layer.
With the 500:
1 - There are damping pads on the sheet metal of the floor - just a few of them and they are of the bitumen type (cheap) - butyl (Dynamat type) is a lot more effective, as it is softer, but obviously that would be more expensive. There are NO damping pads on the rear wheelarches inside the rear quarters, and the damping pads on the rear quarters and doors are stingy in the extreme. I estimate about 10% coverage. The area under the rear seat has no damping pads, and this is relatively close to the rear suspension pickup points, so another area needing improvement.
2 - The fairly soft carpet has generous pads of fluff glued onto it. They are a decent thickness and seem quite good quality. Inside the rear quarters there is a thick strip of fluff BUT it sits on the undamped sheet metal, so is probably not very effective.
3 - Not present...!
Yes, FIAT seems to have forgetten the constraining layer - the floor is like an open sandwich and your eardrums are the top layer... Assuming the floor radiates structure-borne noise, there is only the carpet on top of the soft layer... and that carpet is thin and soft.
My guess is that the original specification might have called for hard plastic-backed carpet as fitted to older FIATs (some barrier capability), but at some stage this was changed to the thin soft stuff as used for (say) speaker box trimming (no barrier capability).
Lift the carpet on a more expensive car and you will find a thick bitumen layer on top of the felt - in fact, the carpet backing will be stuck to the bitumen from melting in the heat. Sometimes the bitumen layer tends to crack from flexing, but in the better-quality cars it has a higher rubber content and is actually quite flexible.
jj_pierce points out the benefits of a constraining layer very clearly in his guide to door treatment, where he applies the constraining layer to the door trim and the felt towards the door. Seems the best approach to me too, though I will also start by removing the polystyrene foam sheet and I shall cover the holes in the door with a relatively hard bitumen sheet moulded to shape with a heat gun. It may soften in the summer, but it won't go far with the felt stuck over it. It will make the door into a better 'box' for the speaker - I've had amazing results from this in the past on 164s - in one case it actually made the door speaker give too *much* bass - had to tune out the booming with the equalizer!
So, the doors are planned out, but what will happen with the 500's floor?
The felt stuck to the carpet is a big problem, as the constraining layer needs to go over this felt and under the carpet. Perhaps FIAT were just trying to make the carpet feel soft underfoot for perceived quality! The felt could be left under the carpet and more felt could be applied to the floor, then the layer, and then the standard felt/carpet, but I think this might all be too thick to fit properly.
I think I will have to take a knife to the existing felt, cutting most of its thickness off (it is hot-glued to the carpet) - not all the thickness has to come off, but I think at least the same thickness will be required on the floor followed by a constraining layer of suitable material.
So, what material to use for this constraining layer, over the fluff on the floor? Damping pads intended for sheetmetal would work, but are expensive and not the most appropriate as they are soft and will become creased/trodden down and move around. Bitumen pads (cheaper) will crack.
I think I have found the solution and it is a combination of the very cheap and the very expensive (sold at a cheap price). I drove around the part of town that has carpet shops, and I found one with a rubbish skip outside. In there, I found offcuts of flooring vinyl. Some of this is soft and useless, but other types (industrial) are hard and very stiff/heavy. This is perfect for the job of sitting on top of the felt - and it's free.
(Incidentally I have also used heavy floor vinyl in the past stuck to sheet metal as a damping pad - I stuck it on with brush-on underseal - a very cheap solution that made a huge difference to FIAT Uno doors! These days for damping pads, I shell out for Dynamat-type damping pads (butyl and aluminium) though they are an imitation sold under a shop brand.)
Back to the topic - constraining layer for floor - I have managed to clear the old stock of mineral-loaded-vinyl rolls from the electronics shop where I used to work. At $35 each for the area of one footwell, and being non-adhesive without butyl, foil, or foam, these weren't a top-seller. At the clearance price of $10 each, I bought all four rolls. I think I have finally found the correct application for them - they will be glued on top of the felt. They are flexible but also a bit heavier than the flooring vinyl, as the material is loaded with barium. I think it is, anyway... isn't barium radioactive? :yum:
From a total of four suppliers, I gathered a range of different materials for a few hundred dollars...
- Six 60x20cm hard self-adhesive sheets from paint/bodyshop supplier, Bostik brand, probably bitumen-based, similar to what FIAT applied. These will be used to cover holes in the doors, moulded to shape with a heat gun. They 'set' into a rigid shape. Don't seem to have an odour. $6 each/$36.
- Five rolls 60x100cm soft butyl/aluminium 'Response' brand (Jaycar Electronics) Dynamat equivalent. Same thickness as Dynamat Extreme and same feel to work with, very adhesive. $30 each/$150. One roll will be used for each door, mainly covering the inside of the outer skin (at least 50% coverage, particularly over the areas damped originally by FIAT). The rest will be used on the floor sheetmetal and rear quarters.
- Two more rolls similar to above but old stock, $20 each/$40, area under back seat and boot floor.
- One roll 60x80cm - as above but with a honeycomb foam included over the foil layer. This turns out to be superfluous, as the felt will be more effective, but I did find a use for this one - inside the door, behind the speaker, on the outer door skin - the foam will dissipate the back waves from the speaker, and if it gets wet, won't stay wet for long.
- Several 'mover's blankets' from a hardware store - a grey felt made of recycled cotton - this is very similar to the material used by FIAT, except thinner (maybe 8mm). At the price of only $9 for several metres, this is so cheap that it could be used in a double thickness and still be only $30-worth for the whole floor.
- The barium-loaded vinyl mentioned above, to go over the felt on the floor. $40. The carpet will then sit on this. Flooring vinyl is the substitute for when the genuine material runs out - perhaps for the rear footwells and inside the rear wheelarches in strips sitting on top of the material that FIAT provides. Also under the rear seat base - the seat base itself is very lightweight foam and would not do the job sitting on the felt by itself.
- what have I forgotten - well, more of the 'mover's blanket' felt in each door and stuck to the back of each quarter panel - the plastic trim panels will provide the constraining layer in these cases, especially if damping pads were applied to the plastic first.
- a few bricks of squidgy foam taken from a wrecked 166, where it is used around the rear struts under the rear shelf (saloon body) - this will be used in the rear quarters of the 500 to reduce sound transmission from the rear end. I noticed a sharp increase in noise level when driving my 500 with rear seats folded down, proving that the rear end needs work to reduce the sound transmitted through the wheelarches and boot floor. The carpet trims in the boot are so thin that they must be very ineffective at damping the sound back there.
- ah yes, I remembered - expanding foam in the crossmember under the seats and in the front corners of the sills - two cans did not go very far for this, but the resulting 'plug' should stop transmission of sound from the front of the vehicle. This is a principle used on the Alfa 156 and 166 and I notice also at the back edge of the 500's sills - near the seatbelt reels in the middle pillars, you find a plastic baffle that contains the black expanding foam underneath. If it's good enough for the back of the sill (to stop the sound from the back), why not at the front too? Ideally all the way along, but there are drainage considerations.
So all this is underway and I have applied the deadening to one door skin - it has already made a difference to the sound of the door closing, which is a pleasing outcome just by itself
I know the weight of adding damping pads (8kg), felt (5kg), and constraining layers (10kg) would be a concern to most people but I see perhaps 20kg as being very worthwhile. This is a road car with a small engine, not a racecar, and quite an expensive small-engined road car - it deserves more refinement, as the Lancia version would have (if there was/is one). The perceived quality of the car is as important to me as its performance! I could always leave the spare wheel at home and keep the fuel tank half full. Also I never carry around toolboxes, fuel containers etc. in my cars...
Of course in the process I had to drill out the rivets that hold the speaker onto the door, and that led to the decision to upgrade the speakers That's pretty much another whole topic of discussion which I shall leave until later...
I will keep things updated here as I make progress. I already have some sound level measurements, all in dB(A), taken at idle and on carefully-defined pieces of local road surface at carefully-defined speeds, and each moving measurement is the average of four measurements (yes, that must have got some odd looks as I made all those U-turns):
500:
Idle (warm engine, ventilation fan/stereo/etc. off) - 46.1
60km/h top gear, new coarse road - 80
80km/h top gear, new smooth road - 73
100km/h top gear, new smooth road - 75
For comparison, same figures in my Alfa 156 before I sold it (only 'average' quietness with no additional soundproofing over standard):
Idle - 51.8
60km/h coarse road - 75
80km/h smooth road - 69
100km/h smooth road - 72.5
And in my 166 (a heavy and quite luxurious car, but also standard):
Idle - 48.4 (that V6 obviously no match for the 1.4L FIRE)
60km/h coarse road - 72
80km/h smooth road - 66
100km/h smooth road - 68.5 - until you stand on the loud pedal, which gives an instant 75dB(A)
Interesting, isn't it, that the difference between the 'average' 156 and the 'quiet' 166 is pretty close to 3dB across the whole range of conditions. I think I recall that 3dB is the 'doubling' of a perceived sound level? - but I could be mixing it up with signal-to-noise ratio in transmission of data in cables (something I studied once).
Obviously my target for the mainly-around-town 500 is to reduce the 60km/h coarse road sound level from an unacceptable 80dB(A) down to perhaps 74dB(A). I'm not concerned about the higher speed sound levels (I actually WANT to hear the engine!) and I don't expect it to match my 166, but anything gained in other conditions will be a bonus, and the stereo will sound better too (my 500 doesn't have Interscope).
Thanks for reading
-Alex
After two hours, I had a garage full of seats and panels, and a 500 that looked like this... (see pics below)
It's clear that the team charged with soundproofing for the 500 Sport were operating on a tight budget. After all, when you have to fit two pretensioners to the seatbelts (one on the reel, one on the lower mounting), side impact G-sensors, curtain airbags, and rear seat ISOfix mountings, there can't be much money left for deadening pads.
What was a real surprise, though, was that it appears that somewhere along the line, a golden rule of soundproofing was ignored
The materials that are there can't work properly because other materials are missing - I'll explain in a moment.Now I can't claim to be a qualified sound expert (uni physics is ten years ago for me and it was mostly about electricity and light), but I have years of experience taking apart cars like Alfa 164s and 166s which have a *lot* of soundproofing that I've studied and removed. For example, I've compared the later 166 with "improved sound deadening package" against the earlier version, to see which areas were improved (the deadening pad under the rear seat has a foil layer, for example, and the felt on top of that has a layer of bitumen where the earlier version does not...) The manufacturers have many tools for measuring and modelling that we do not have, so it makes sense to see where they decided to make improvements when the purse strings were loosened. Who would have thought that noise came from under the rear seat...
And of course, I've read lots of pages about the subject. There is a clear difference between how soundproofing is applied in the aftermarket (typically to hot-rods and other bare-metal restorations) and how the OEMs do it. The sellers usually want to sell more of their product, but I think a good example of fairly-unbiased (!) advice is http://www.sounddeadenershowdown.com/cgi-bin/index.cgi
In the aftermarket, you generally see everything covered wall-to-wall with Dynamat or a similar damping layer, which has a foil top surface. Some people leave it at that, but the better people go on to add a layer of 'fluff' (recycled cotton felt/underlay) - as our own pierce_jj shows in his excellent guide.
Incidentally I'm not out to disprove what pierce_jj has (successfully) achieved and shared - I found it inspiring - I only want to add a little more of my own thoughts and methods as my project progresses.
The golden rule of successful sound deadening seems to be to make a 'sandwich':
1- Damping pads on sheet metal to control resonance (ringing like a bell is stopped by 25%-50% coverage, no need to go wall-to-wall)
2- What I call the "fluff" - or foam - a soft layer that dissipates higher-frequency sound energy
and then:
3- constraining layer - a relatively thin but heavy surface that traps the sound in the soft layer.
With the 500:
1 - There are damping pads on the sheet metal of the floor - just a few of them and they are of the bitumen type (cheap) - butyl (Dynamat type) is a lot more effective, as it is softer, but obviously that would be more expensive. There are NO damping pads on the rear wheelarches inside the rear quarters, and the damping pads on the rear quarters and doors are stingy in the extreme. I estimate about 10% coverage. The area under the rear seat has no damping pads, and this is relatively close to the rear suspension pickup points, so another area needing improvement.
2 - The fairly soft carpet has generous pads of fluff glued onto it. They are a decent thickness and seem quite good quality. Inside the rear quarters there is a thick strip of fluff BUT it sits on the undamped sheet metal, so is probably not very effective.
3 - Not present...!
Yes, FIAT seems to have forgetten the constraining layer - the floor is like an open sandwich and your eardrums are the top layer... Assuming the floor radiates structure-borne noise, there is only the carpet on top of the soft layer... and that carpet is thin and soft.
My guess is that the original specification might have called for hard plastic-backed carpet as fitted to older FIATs (some barrier capability), but at some stage this was changed to the thin soft stuff as used for (say) speaker box trimming (no barrier capability).
Lift the carpet on a more expensive car and you will find a thick bitumen layer on top of the felt - in fact, the carpet backing will be stuck to the bitumen from melting in the heat. Sometimes the bitumen layer tends to crack from flexing, but in the better-quality cars it has a higher rubber content and is actually quite flexible.
jj_pierce points out the benefits of a constraining layer very clearly in his guide to door treatment, where he applies the constraining layer to the door trim and the felt towards the door. Seems the best approach to me too, though I will also start by removing the polystyrene foam sheet and I shall cover the holes in the door with a relatively hard bitumen sheet moulded to shape with a heat gun. It may soften in the summer, but it won't go far with the felt stuck over it. It will make the door into a better 'box' for the speaker - I've had amazing results from this in the past on 164s - in one case it actually made the door speaker give too *much* bass - had to tune out the booming with the equalizer!
So, the doors are planned out, but what will happen with the 500's floor?
The felt stuck to the carpet is a big problem, as the constraining layer needs to go over this felt and under the carpet. Perhaps FIAT were just trying to make the carpet feel soft underfoot for perceived quality! The felt could be left under the carpet and more felt could be applied to the floor, then the layer, and then the standard felt/carpet, but I think this might all be too thick to fit properly.
I think I will have to take a knife to the existing felt, cutting most of its thickness off (it is hot-glued to the carpet) - not all the thickness has to come off, but I think at least the same thickness will be required on the floor followed by a constraining layer of suitable material.
So, what material to use for this constraining layer, over the fluff on the floor? Damping pads intended for sheetmetal would work, but are expensive and not the most appropriate as they are soft and will become creased/trodden down and move around. Bitumen pads (cheaper) will crack.
I think I have found the solution and it is a combination of the very cheap and the very expensive (sold at a cheap price). I drove around the part of town that has carpet shops, and I found one with a rubbish skip outside. In there, I found offcuts of flooring vinyl. Some of this is soft and useless, but other types (industrial) are hard and very stiff/heavy. This is perfect for the job of sitting on top of the felt - and it's free.
(Incidentally I have also used heavy floor vinyl in the past stuck to sheet metal as a damping pad - I stuck it on with brush-on underseal - a very cheap solution that made a huge difference to FIAT Uno doors! These days for damping pads, I shell out for Dynamat-type damping pads (butyl and aluminium) though they are an imitation sold under a shop brand.)
Back to the topic - constraining layer for floor - I have managed to clear the old stock of mineral-loaded-vinyl rolls from the electronics shop where I used to work. At $35 each for the area of one footwell, and being non-adhesive without butyl, foil, or foam, these weren't a top-seller. At the clearance price of $10 each, I bought all four rolls. I think I have finally found the correct application for them - they will be glued on top of the felt. They are flexible but also a bit heavier than the flooring vinyl, as the material is loaded with barium. I think it is, anyway... isn't barium radioactive? :yum:
From a total of four suppliers, I gathered a range of different materials for a few hundred dollars...
- Six 60x20cm hard self-adhesive sheets from paint/bodyshop supplier, Bostik brand, probably bitumen-based, similar to what FIAT applied. These will be used to cover holes in the doors, moulded to shape with a heat gun. They 'set' into a rigid shape. Don't seem to have an odour. $6 each/$36.
- Five rolls 60x100cm soft butyl/aluminium 'Response' brand (Jaycar Electronics) Dynamat equivalent. Same thickness as Dynamat Extreme and same feel to work with, very adhesive. $30 each/$150. One roll will be used for each door, mainly covering the inside of the outer skin (at least 50% coverage, particularly over the areas damped originally by FIAT). The rest will be used on the floor sheetmetal and rear quarters.
- Two more rolls similar to above but old stock, $20 each/$40, area under back seat and boot floor.
- One roll 60x80cm - as above but with a honeycomb foam included over the foil layer. This turns out to be superfluous, as the felt will be more effective, but I did find a use for this one - inside the door, behind the speaker, on the outer door skin - the foam will dissipate the back waves from the speaker, and if it gets wet, won't stay wet for long.
- Several 'mover's blankets' from a hardware store - a grey felt made of recycled cotton - this is very similar to the material used by FIAT, except thinner (maybe 8mm). At the price of only $9 for several metres, this is so cheap that it could be used in a double thickness and still be only $30-worth for the whole floor.
- The barium-loaded vinyl mentioned above, to go over the felt on the floor. $40. The carpet will then sit on this. Flooring vinyl is the substitute for when the genuine material runs out - perhaps for the rear footwells and inside the rear wheelarches in strips sitting on top of the material that FIAT provides. Also under the rear seat base - the seat base itself is very lightweight foam and would not do the job sitting on the felt by itself.
- what have I forgotten - well, more of the 'mover's blanket' felt in each door and stuck to the back of each quarter panel - the plastic trim panels will provide the constraining layer in these cases, especially if damping pads were applied to the plastic first.
- a few bricks of squidgy foam taken from a wrecked 166, where it is used around the rear struts under the rear shelf (saloon body) - this will be used in the rear quarters of the 500 to reduce sound transmission from the rear end. I noticed a sharp increase in noise level when driving my 500 with rear seats folded down, proving that the rear end needs work to reduce the sound transmitted through the wheelarches and boot floor. The carpet trims in the boot are so thin that they must be very ineffective at damping the sound back there.
- ah yes, I remembered - expanding foam in the crossmember under the seats and in the front corners of the sills - two cans did not go very far for this, but the resulting 'plug' should stop transmission of sound from the front of the vehicle. This is a principle used on the Alfa 156 and 166 and I notice also at the back edge of the 500's sills - near the seatbelt reels in the middle pillars, you find a plastic baffle that contains the black expanding foam underneath. If it's good enough for the back of the sill (to stop the sound from the back), why not at the front too? Ideally all the way along, but there are drainage considerations.
So all this is underway and I have applied the deadening to one door skin - it has already made a difference to the sound of the door closing, which is a pleasing outcome just by itself
I know the weight of adding damping pads (8kg), felt (5kg), and constraining layers (10kg) would be a concern to most people but I see perhaps 20kg as being very worthwhile. This is a road car with a small engine, not a racecar, and quite an expensive small-engined road car - it deserves more refinement, as the Lancia version would have (if there was/is one). The perceived quality of the car is as important to me as its performance! I could always leave the spare wheel at home and keep the fuel tank half full. Also I never carry around toolboxes, fuel containers etc. in my cars...
Of course in the process I had to drill out the rivets that hold the speaker onto the door, and that led to the decision to upgrade the speakers
That's pretty much another whole topic of discussion which I shall leave until later...I will keep things updated here as I make progress. I already have some sound level measurements, all in dB(A), taken at idle and on carefully-defined pieces of local road surface at carefully-defined speeds, and each moving measurement is the average of four measurements (yes, that must have got some odd looks as I made all those U-turns):
500:
Idle (warm engine, ventilation fan/stereo/etc. off) - 46.1
60km/h top gear, new coarse road - 80
80km/h top gear, new smooth road - 73
100km/h top gear, new smooth road - 75
For comparison, same figures in my Alfa 156 before I sold it (only 'average' quietness with no additional soundproofing over standard):
Idle - 51.8
60km/h coarse road - 75
80km/h smooth road - 69
100km/h smooth road - 72.5
And in my 166 (a heavy and quite luxurious car, but also standard):
Idle - 48.4 (that V6 obviously no match for the 1.4L FIRE)
60km/h coarse road - 72
80km/h smooth road - 66
100km/h smooth road - 68.5 - until you stand on the loud pedal, which gives an instant 75dB(A)
Interesting, isn't it, that the difference between the 'average' 156 and the 'quiet' 166 is pretty close to 3dB across the whole range of conditions. I think I recall that 3dB is the 'doubling' of a perceived sound level? - but I could be mixing it up with signal-to-noise ratio in transmission of data in cables (something I studied once).
Obviously my target for the mainly-around-town 500 is to reduce the 60km/h coarse road sound level from an unacceptable 80dB(A) down to perhaps 74dB(A). I'm not concerned about the higher speed sound levels (I actually WANT to hear the engine!) and I don't expect it to match my 166, but anything gained in other conditions will be a bonus, and the stereo will sound better too (my 500 doesn't have Interscope).
Thanks for reading
-Alex
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