Is it in the engine bay around the serpentine belt area? Could be a pulley. Remove the belt and with the engine off spin the pulleys by hand and see if any make a noise.
If it's not a pulley or serpentine belt it may be the cam synchronizer assembly. The synchronizer shaft has a bearing that makes a chirp when it begins to fail. Google this part for your make and model for a better description of symptoms and how to repair.
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