What causes a chirp?

In loudspeakers.
A bird inside your speaker.

Possible cause of the chirping may be the home security system or a wireless computer device such as a wireless modem or router broadcasting into the surround area and being picked up by your equipment

I seem to remember something about the ISP's incoming signal for the computer modem Pinging it

Just a WAG  

+1 on the bird inside the speaker, especially if its a ported design.
You're a riot, Alice . . . A regular riot!

Do you have a solid state amp or a tube amp? Tubes going bad are notorious for producing funny noises, sometimes chirps. If you don't use tubes, a chirp could be a voicemail rubbing. 
Thanks davehrab.
I'm with you ncarv-
"just one more time Alice"
Thanks reubent. I realize you men voiceboil..
dang autocorrection. voicecoil......

Peter ... I once had a pair of Sota 3 way speaker that I wired backwards .. sent the power from the amp to the woofer and then jumped the midrange from the woofer and jumped the tweeter from the midrange ... this created quite a draw on the woofer and did something to the woofer's impedance ... this caused the woofer voice coil to constantly bottom out on peak passages and the woofer would make a very loud and frightening bang or clacking sound ... I don't think this is your problem  

The single chirping sound you are hearing may be caused by what is referred to as Modem Ping being pick up as airborne
born RF by your low level ICs or a low level component  ... the ping is used to test the circuit or verify a connection ... I also believe hacker use this type of Ping to try and enter your system by verifying  that your modem is in service and your computer is turned on 

I also wouldn't rule out your alarm service pinging your house's security system to verify it's connection   

Try removing the cable feed from the street that goes to your computer modem's input and see if the chirping goes away ... you may also want to take a look at your home security feed from the street  

here's some info I dug up on the net about modem ping  






Enter your text ...
I find changing the battery in the smoke detector eliminates this chirp!

....voiceboil Was funnier, though..made me think of quiet annoyance rising to a crescendo of rage.  Made me stop to consider where I've seen that....

Oh, yeah...the 'whose cables' better' forums...;)
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

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..