LOL!

The famous Chatter :)

If you mimic the call back at her, she'll chatter back at you. I've never
read anything on why cats do this, but I think it's got something to do with
co-operative hunting (similar to lions), because a cat will respond to this
call with intense interest if they hear it (and to human mimicry). The call
is actually in two tones. The lower tones we can hear, the higher
frequencies are beyond our range. However my sister's cat Tom has a very
deep voice and you can hear both parts of the call - a quick modulation
between high and low tones.

Another thing: if you stare intently out the window where your cat can see
you, and start chattering (and if you get it exactly right ;) they start
looking in the same direction for whatever has caught your attention. It's
rather fascinating.

TK