C5X soundproofing

[DS9]

After getting my new car I always want to make it quieter. I've just been out tonight and sound tested it on 2 routes, I hold the phone in my left hand.

1) A drive at a steady 45mph in the centre lane of a 50mph road. Max Esave on. Average 78Db.

2) A few laps at the end of a tesco car park travelling at 10mph, electric mode. Average DB 65Db.

Tomorrow I'll start sound deadening the car and I'll see where I get to. I won't retest until I've finished the job, and when I've got the car mats it hasn't got now.

It's all a bit relative rather than actual but I'm hoping for quite large gains when I retest. It is worth noting the Db scale is logarithmic so 10Db higher from any level is actually doubling the sound. On that basis maybe low 70's and low 60's would be a reasonable expectation.

[DS9]

I think I may have got the maths wrong. This is an AI overview of the difference between 65Db and 78Db.

"A 78 dB sound is approximately 20 times more intense than a 65 dB sound. Each 10 dB increase represents a tenfold increase in intensity. Therefore, a 13 dB increase (78 - 65) is more than a 10-fold increase but less than a 100-fold increase.
Here's a breakdown:
10 dB increase: 10 times more intense.
20 dB increase: 100 times more intense.
13 dB increase: Falls between 10 and 20 dB, closer to 20 dB.
Therefore, 78 dB is roughly 20 times more intense than 65 dB"

[mickthemaverick]

Back in the day working in telephony we always regarded a 3dB increase as doubling the sound level. So 65 -68 double, onto -71 4 times, onto-74 8 times, onto -77 16 times etc.........

[myglaren]

Back in the day working in telephony we always regarded a 3dB increase as doubling the sound level. So 65 -68 double, onto -71 4 times, onto-74 8 times, onto -77 16 times etc.........

That has always been my understanding of it.

[DS9]

That makes sense and kinda correlates ballpark to 65db to 78db being 20 fold ish.

Did the front today at a leisurely pace, took about 4 hrs. There is a balancing act between putting too much in and then you can't affix the plastic wheel well back.

Hardly anything in there apart from very light cotton tampon type stuff when I looked, I just ripped em all off.

The rears are a lot easier, will do those tomorrow. Then it's into the easy stuff.

Random pics below. By the time I put it all back together there was dodomat shiny stuff on both the liners and body with closed cell foam on top. Some screws were hard to get back in but that tells me it's snug which is what I want.

[DS9]

Did one of the rear wheel wells today, took a long time.Nothing in there at all sound deadening wise. In some places I put in 2 to 3 layers of dodomat plus 2 layers of foam on top

Used up probably the same amount on one rear wheel as I did on both the fronts yesterday. It's all gone now so will order some more.

When I'm done I can't wait to see what the difference is.

[Vic Evans]

Did one of the rear wheel wells today, took a long time.Nothing in there at all sound deadening wise. In some places I put in 2 to 3 layers of dodomat plus 2 layers of foam on top

Used up probably the same amount on one rear wheel as I did on both the fronts yesterday. It's all gone now so will order some more.

When I'm done I can't wait to see what the difference is.

I'll be quieter but thirstier with all that extra weight to lug around

[mickthemaverick]

Did one of the rear wheel wells today, took a long time.Nothing in there at all sound deadening wise. In some places I put in 2 to 3 layers of dodomat plus 2 layers of foam on top

Used up probably the same amount on one rear wheel as I did on both the fronts yesterday. It's all gone now so will order some more.

When I'm done I can't wait to see what the difference is.

I'll be quieter but thirstier with all that extra weight to lug around

Is the stuff you are using fire proof?

[DS9]

I thínk I'll add maybe 30-35kgs by the time it's done, about 2% or less. I'll be fine with fuel consumption dropping by a similar amount as long as I see a significant sound reduction.

As for fire proof. No it's not. Fire retardent. This is the kit I got.... And now need another. https://www.dodomat.com/products/dodo-mat-car-kit

In the 500x is put 2 layers of the hex stuff under the bonnet, made the rattly diesel a lot quieter. In the DS9 I got the engine bay mat, costs about £40 is quite thick and probably the best solution for the bonnet. In both cases i never had any issues.

[DS9]

Tried it tonight with just 3 wheels done.

Compared to both original examples the Db meter read 1 less. This is subjective to a degree because of the rounding element. The tesco car park may have just dropped from 64.6 (rounded to 65) to 64.4 (rounded to 64, almost nothing. Conversely it could be 65.4 rounded to 63.6 which could be almost 2. The 46 mph route was reading 77 but I left it too late, hit a rough patch and it rose back to 78.

I'll just take it as 1Db.

The road noise still seems to be in the floor. I think the boot will make a big difference when I get onto that.

Going off the comments on here I'd be delighted if I could get to 62Db from an original 65Db.

[DS9]

I've managed to get more precise detail via the app graphs and it's given me greater clarity. I'd have hated to have done what I have so far for a miniscule gain.

On the 45mph route there is a range from about 10 seconds to 95 seconds, so give or take a minute and a half where the readings are quite flat. I can't get actual readings but i can eyeball the graphs. There is a clear drop in the readings, the original over this range was centred around 77 (ish) and now its around 76 (ish), so we could say a 1Db drop. Top level estimate.

However I've then had a good look in the lower range 74.5 to 76 original and 73.5 to 75 new. Whichever of these shows "more green" adjusts the original 1Db up or down. After eyeballing them I can't really ascertain which is the winner so I'll stick with my original 1Db improvement, say a range of 0.9-1.1,

[mickthemaverick]

I have to say I have never known anyone, in 55 years of motoring, put so much effort into sound deadening. In fact I don't recall anyone putting any effort in at all!! Would it not be easier to use cotton wool in your ears?

[DS9]

If I can get to 3Db I'll say it's well worth it. Maybe 2 days labour and £170 quid to have a car for years that I'm happy with. I can live with the downside of a couple of percent higher mpg.

Its more common than you'd think. With electric cars such as Teslas having very low noise apart from road noise it is quite common these days to improve it.

[myglaren]

I have to say I have never known anyone, in 55 years of motoring, put so much effort into sound deadening. In fact I don't recall anyone putting any effort in at all!! Would it not be easier to use cotton wool in your ears?

Noise cancelling headphones?

[the-termin8r]

I have to say I have never known anyone, in 55 years of motoring, put so much effort into sound deadening. In fact I don't recall anyone putting any effort in at all!! Would it not be easier to use cotton wool in your ears?

The pursuit of silence is a brutal one. I've considered adding sound deadening to my X7, but having just swapped the door cards over the weekend (no sound deadening added) I don't think it's worth the faff.

Also as a pedantic side note for OP: Db isn't a unit of measure, it's dB.