You may want to go over both speakers and make sure all the nuts and bolts are tight. Pay extra attention to the grill cover and feet. If any of the fasteners/inserts worked themselves loose, the noise could be caused by the metal/plastic inserts rubbing against the wood.
It would be a good idea to list your entire system. The problem may lie somewhere else. For example, if you have any type of computer audio setup, its common to have the usb 2 system overloaded without realizing it. If the computer has trouble keeping up with everything, you will definately here some strange noises, including a chirp.
