CPU emitted dog barks

i don't know if i mentioned this in passing in another thread but this even has the apple care people stumped. on two occasions suddenly the computer started barking at me! a couple of barks each time. the first time it scared the living daylights out of me and i thought it must be coming from some website i was on, like there was a dog animation or something but when i looked through all the open browser windows there was no such thing. i probably had a word doc open and the mail program, too. the usual. no special applications running.

the second time i thought maybe it was some kind of alert (even though i have my alert sound set to "tink") for a pop-up window. and, sure enough, when i started getting rid of open windows to identify the problem there was a small pop-up netflix window but i am still not convinced that was it. first of all, with alerts in general, shouldn't they be visual as well as audio? what if i were deaf and there were a problem? if i didn't hear the audio i would never know.

anyway, like i said, nobody i've spoken with at apple has a clue, nor have they heard of this before. it hasn't happened in a while. if it does again i will be sure to note the time and what i was doing but the whole thing freaks me out a bit because, as per usual, when anything weird happens like this i think it's a symptom of something major going wrong and as i just got this new g5 3 weeks ago it makes me nervous to contemplate such a thought.

any clue?