My RT43's became noisy at approximately 40K miles +/-, about a year ago. They are rotated every 6,000 miles and seen to have no wear irregularities, very even in fact. My bearings seem o.k. (how does one diagnose bad bearings beyond roughness and/or excessive play?).
It's very difficult to describe the noise. Definitely rhythmic depending on speed. Not quire a hum. Not quite a thump. It does change with the type of road surface. The noise doesn't seem to change with a rotation.
I plan to replace them before the upcoming winter. Debating what to buy. The literature states that these tires have built in features to limit noise. I suspect maybe it is some kind of internal damage due to our road conditions (can anyone elaborate about internal damage?).