Thanks andylong your input, my friend said that the vast majority of road noise comes from the tires, so we should address the condition of the tires first to reduce the noise they produce.
At the same time, I also hope to add more soundproofing materials to further improve the situation. However, removing some interior parts and then restoring them is a big challenge for me, as I tend to break things every time I try to do so.
Thanks tomosllyr your sharing, I have been searching for some materials to treat the boot floor because it can be done without removing any parts, which seems worth a try.
Could you share what materials you used to treat the rear trunk floor?
By the way, I noticed that when there are passengers in the rear seats, the road noise seems to improve. Apparently, something is dampening the road noise coming from the boot floor and directing it towards the rear seats.
I used Silent Coat 2mm