These are Nokian enTyre 2.0s. They have 23k miles on them, wearing evenly, been installed since May 2018 (DOT code 0717). If you look closely, you can see cracking in between the tread blocks, as well as on the edge where the tread meets the sidewall. Normally this cracking doesn't bother me, but after a recent tire rotation, these tires have been quite loud. There are no vibrations or pulling or anything else odd, but the fronts especially make a "wup-wup-wup-wup" noise occasionally at certain speeds. Ride has been rougher lately too, and I occasionally get wheelspin from a wet stop which I normally don't. These were bought off eBay, so no real recourse or warranty in this case. Lesson learned I suppose. What's going on here?