Understanding how different type of roads impact noise levels

There's a road near me that is quite noisy, but one stretch of it has been recently resurfaced and the silence inside the car is unheard of, pun intended.

That gave me an idea to do a noise measure in this road to compare the silence of brand new asphalt to old rough and noisy asphalt.

Opel Ampera
Opel Ampera

I did the test at 80km/h only, since the limit there is 100km/h, so no way to test the noise at 120km/h. The noise level at 80km/h in the usual road I use to do this was 54 dB.

On this road in the rough asphalt the noise level would go as high as 58dB, the same noise level as I usually get at 120km/h on other roads.

But once I got into the new piece of road the noise level would go down to 49dB, 5dB less than on my usual road and 9dB less than the rough asphalt.

This is why it's important when deadening a car to use always the same road to make sure you get accurate results when comparing the before and after. This also means your results might vary, if you own an Ampera with the same set of tyres and do the exact same thing I did to my car and you live in Norway were the roads are a bit noisier due to their composition to withstand harsh cold weather you won't get the same dB levels and I do in Portugal.

But this also means the car could be quieter with less rolling noise.

Should I do anything to make the car even quieter?

Last time I did anything on the Ampera related with sound deadening was back in March 2019 and I really think the car is quite nice as it is now, only complaint really is with the side windows.

I even had the seats out of the car to redye them and just looked at the deadening material to see if everything was in place and didn't bother to add anything else.

A nice and quiet place
A nice and quiet place

But this road resurface got me thinking. I didn't got a great result deadening the wheel wells on the C6 but those are fabric and already had some deadening in them.

Maybe adding MLV to the wheel wells on the Ampera would work, I might take the splash guards out and see if there is any possibility to have the MLV kept in place with some screws or something similar. With I could find online there's a lot of cables there for the charge port and I really don't feel comfortable creating holes in the car just to hold the MLV in place.

I could do the opposite and stick the MLV into the splash guard, but those usually are plastic and I don't know if they can hold the weight of MLV.

I'd say the car for now is finished, but who knows.

Opel Ampera
Done in 27 of August, 2020