High pitched siren sound when accelerating

I started my car and have a high pitched siren sound. It gets extremely high as I accelerate and almost goes away - but as a slow down it is loud again.

Any ideas?

can you tell me year, make model of your truck?

also can you tell where its coming from? front? back? maybe a stuck caliper?

2000 chevy blazer - it is coming from the front - I can here it throught the the heater/defrost on the dashboard

oh THATS a wierd one.... does it happen when the ac is off, on or does it matter?

you can her is slightly when the stopped but very lough when I am accelerating - quite annoying

typing and eating is not a good thing - boy oh boy the incorrect spelling - what I meant is you can hear it slightly when stopped but very loud when I am accelerating - quite annoying

Are you talking about a "swooshing" sound possibly coming from the heater core? If so do a search on this site there are other posts with good info for this problem.

Is the noise engine RPM dependant? or is it more speed dependant? If it's speed, you really need to check the brakes as Dory has suggested.

If it is more rpm dependant, I would start by checking your serpentine belt for cracks or other signs of wear. If you cannot ever remember changing the belt, now would be a good time. You don't want something like that to break. While you have the belt off, you could check the A/C compressor, compressor clutch, and pulley. The compressor should turn with a bit of resistance, but not much. If you can see rust on the clutch plates, that could also be your problem.

If it is neither rpm or speed dependant, it could be the hvac fan in the dash, but I do not think that a problem with a heater fan would be classified as a siren...