My car has been making a whistling noise. It's there when you turn ignition on and it gets louder as you press the accelerator and start off in first and progress - it sounds a bit like a siren! By the time you get up to around 30-40 mph it has either stopped or is inaudible. The alternator warning light flashed for a second or two the other day when I was parking but has been okay since. I took it to the garage and they have replaced the fan belt and automatic tensioner, but the noise is still there. Has anyone any ideas what it might be? thanks.