Long story short, my Seat Leon (2014 1.6 TDi) is hugely quieter than my wife's Hyundai i30 (2018 1.6 TDi), particularly at cruising speeds of 60+ mph. Even an hour trip just gives me a headache after a while. It sounds like road noise, a low rumbling - it may not actually be a difference in pure dB but maybe just a difference in pitch that makes it much more annoying? The Seat Leon has cheap Toyo tyres, whereas the i30 has supposedly good Michelin Primacy 3s that came with the car when she bought it (225/45 R17). Are there any alternatives that are quieter? Any other changes that can be made aside from the tyres to reduce road noise?
Thanks for any advice.