hi i have a fiat bravo tjet 150 sport 2007 and a few days ago I could slightly hear this noise around 30mph sounded like a humming that oscillates in pitch and volume in accordance with the speed of the car so going to jack it up tonight and have a feel of all the wheels , what should I look out for ? wheel bearing ? stepping on tyre ? warp on disc ? if anyone with any experience or that has had this issue could help would be much appreciated thankyou