Whining/Vibration - Nissan X Trail

[Otto1968]

Have a 66 plate X Trail, 2 wheel drive. At about 25-30mph it develops a whining noise and I can feel a vibration through the floor panels. Had 4 new tyres put on and balanced, still there. Its not coming through the steering wheel and doesnt affect braking, I'm leaning towards something to do with rear wheels, passengers say it seems louder in the back. Nissan looked at it and said 'loose items in boot' lol, obviously didn't take it out for a drive. Having it serviced next week but wanted to give them some pointers rather than just get fobbed off again. Could it be a wheel bearing or something else? Thanks for the help.