What causes a chirp?

Well tks matt,; and asvjerry - I like that. As little Johnny says "It shows you're thinking".
Davehrab I appreciate your comments and will explore your links.
Cheers; it's time for some B&B. Bach and Brandy...

What causes a chirp?

In loudspeakersptss

If it happens around the same time of day, in my HT setup it's the off peak hot water mains signal coming through the system.

Cheers George

pass,

Tell us more about the chirp. When does it happen? What is the frequency of it happening? What is the duration? Is it from one speaker or both? Do you have any tubes in your system?

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. 

Thanks to allI found the cause of the chirp-
It was the sound of all the "birds" promoting the
SR Red and Black "Quantum"  fuses, non sense..