'Thrumming noise' at 50 mph and above

Just had 2 new rear tyres fitted (Michelin Lattitudes) on my Freelander - the original Michelins having done 96,000 miles! I've now started to get a strange noise - best word i can think of is thrumming. It starts at around 50 miles an hour and is like a buzz that reaches a peak and then fades away to nothing then comes back again in a regular pattern.. As you accelerate it too speeds up but at a much lesser pace.

Leave for work and return home in the dark so haven't yet had chance to have a shuftie underneath.

Any thoughts appreciated.

If it only started after the tyres were fitted, thats a good pointer.

Are they 'handed' treads?? Maybe on backwards

Its not unusual to get a noise simular to a wheel bearing going with new tyres normally goes after a few miles once the tyres have run in, its because the tread is square and the leading edges need to wear down slightly.

Firstly - apologies to Dave and Oldskool for not thanking them for responding. Left is a week or so to see if things settle down - but problem still persists. As said before had 2 new rear tyres put on at a place I've used for years but which has just changed hands. When got around to having a shufftie, 1 tyre was at just under 30psi and the other over 40!!! Put both to 30 and thought threre was an improvement but actually turns out to be wishful thinking. Just as bad - in fact now noticeable when travelling under 50 mph. Any thoughts anyone?

swap em front to back? see if the noise moves or it turns into steering wheel vibration or something will tell u if it's tyres or bearings.