Check out various threads in the Forum on noise reduction. There are some cheap and easy ways of reducing noise and then from there some increasingly labor-intensive means. Here's what we've done to our cars:
1) the first thing that we did which was reasonably effective was the RPM Tesla wind noise reduction kit. Although this doesn't address tire noise it does make a difference in terms of overall noise levels allowing you to at least drop a couple of DB, and then you can attack the tire noise with interventions 2 through 4. And this is more and more noticeable as speeds pick up on the highway. In other words, wind noise at 55 isn't so bad but it's 75 it's really noticeable. If you don't want to pay for this you can get solid quarter inch neoprene tubing off of Amazon. It's pretty cheap and it actually fills the space a little bit better but it's not as easy to get in and sometimes it can work its way loose since it's not a continuous piece. But if you use both the RPM noise reduction kit and the solid neoprene together you can fill all the channels in the roof glass.
2) doubling up on the door seals. This makes probably the biggest difference of any single intervention if you do it properly. Again you can Google threads on door seals and see how people have done it and what the results are and once again there is now a specific kit on Amazon that allows people to do this. We did it ala carte with our own Z & P door seals. What we found however was that without putting double sided 3M tape on the door seals regions first, the Cheapo version of it that comes on the door seals just doesn't hold up 4 long no matter how carefully you clean the metal surfaces before application. With a doubling up on the double-sided tape we have had them last for a year plus.
3) closed cell foam underneath the wheel liners in the wheel well areas. This is definitely a lot of work and I've only done one so I don't have measurements or actual data to support its Effectiveness. It's a lot of work, but I believe it probably will suppress tire noise significantly.
4) dynamatting just about everywhere you can think of. This is the most labor-intensive and may have the lowest yield per man-hour of work and cost. However after dynamating the doors and the rear trunk the doors all close in a much more solid sounding and less tinny fashion (it's now a satisfying thunk instead of a collection of rattles). I believe this got me an additional 2 DB of noise suppression but again it was an amazing amount of work. I did not Dynamat the floor pan because I don't think that pays much dividend.
5) last but certainly not least when it's time to replace your tires see which tire tire rack rates highly in terms of noise. Certainly we've been pretty pleased with the Michelin Pilot Sport 4S – great performance, good ride and reasonably quiet. I don't know what it's noise ratings are relative to the Continental tires that come with the car. Never been terribly impressed with Continental Tires since I had a pair many years ago but again check out the Tire Rack rating on both on the so-called ultra-high-performance all seasons Tire group and summer max performance tires that offer a quiet ride. If your ZIP code is correct you're obviously going to need some winter performance and you may not want to have two sets of tires. I would recommend the Michelin Pilot Sport All Season 3 plus but it is a bit noisy and that may not be a great match for you. It is an amazing Tire in terms of offering decent winter and great wet and dry traction. But it does sing.
The new cars probably come with additional sound deadening material around the wheel wells, and I suspect the trunk area as well along with I reported thicker acoustic glass. I'd love to measure one of them and compare it to one of our customized dual motor performance models. I believe I got somewhere around 5 to 6 DB of total noise suppression from all my efforts. But this is obviously not something that the average user wants to do. I would say for sure that the two interventions that pay the best return on investment so to speak both in terms of time and money are simply the RPM Tesla wind noise reduction and then the door seals. Sorry for the long winded post but I hope that's helpful.
Lots of good points by @dfwatt. The fact your van is quieter is likely due to a multiple of factors other than just tires. I'd guess that if you put a set of Tesla spec foam lined tires (if they even had the size) on your van, it would be as quiet if not more so than the current Michelins you have on there. The Continentals, as well as other oem Tesla tires, are engineered specifically to be quiet so even if you happen to find a so-called quieter non-Tesla spec tire, it may not be the difference you are looking for. Try some of the suggestions listed above and welcome to TMC.