Unusual warning noise/tone

Mazda3 2012
Hi All,
I have a 2012 Mazda3 hatch, auto, and every couple of months it will suddenly start making a warning tone from somewhere in the dash. Note this is not the usual Mazda chime that warns of doors/lights/seatbelts etc.

Instead it sounds like an electronic timer (beep or buzzer), 2 to 3 beeps per second, and lasts for about a minute then stops. No warning lights on the dash or the info display, and the car continues to drive normally. Sounds just like an alarm clock is hidden in the dash somewhere...

I've had the car 8 months, and it has made this sound 3 times, each at different times of the day and driving conditions. Mazda dealer doesn't have any ideas...

Any thoughts from the collective minds?
Mazda3 2012
OK, a followup on this, I think we've solved it.
Tucked in next to the battery was an electronic box labelled CECI, as far as I know it stands for Computerised Electronic Corrosion Inhibiter. These have been identified by Western Australia Consumer Protection as having false and misleading claims....

I've disconnected it, and no more unusual beeps for nearly 10 months...