i have a 2002 petrol fiesta. It makes a strange humming / howling sound (like wind through wires) when i drive. It does not make the sound when standing still. I still hear the sound when i drive and dip the clutch and also when i pull out of gear and coast. It seems to be louder when i slow down to stop. The engine ticks over fine - i have had new tyres just over a month ago - the garage seems to think its the tyres - but i dont think so. i am sure the sound was there before but not so loud. It does not seem to matter what speed i go neither nor road surface. any ideas please