2007 Yaris Chirp (not a squeal)

[Nachal]

My 2007 Yaris started doing a single chirp every minute or so. It sounds like a smoke detector when it has a low battery.
There are no error lights on, and it is not coming from the sound system, as it is still happening when the sound system is off. I can't locate exactly where it is coming from, and I couldn't find anything on here or Google.
Any ideas as to what it is?

[komichal]

Does this happen only for some time and does it go away after some longer drive?
Is the AC on or off during that time period?
Do you still have original belt or any replacement already happened?
When driving, does the noise from the engine mask the chirp or can you hear the chirp over the engine noise?
If possible, try to record it and post it on youtube.
I had some strange irregular chirps in the past. Changing belt did not help but changing pulleys did. I never figured out which one it was. Who knows if this is the same problem.