i have recently noticed and was also told by a passenger that my octy has started to make a funny noise when i am driving.it is almost like a humming noise and the higher the revs the quicker the hum.i could have swore it was never there before and when my mate said the same to me without prompting i knew i was right.it happens at around 40+ mph and even more so at motorway speeds in 5th i know my tyres are getting on the bald side and i am wondering if this may be the cause.if anyone knows what this is could they please let me know thanks

sounds like a wheel bearing to me, jack each corner of the car up and check each wheel for any play, rear bearings aren't too difficult, but the fronts are a lot more involved! failing that, swap your front and rear wheels over (front to rears, rears to front) this should eliminate your tyres being at fault, unless your rears are as worn as the fronts? hth

it happens every time i take my foot off the accelerator and it sounds like the engine braking.