Sure doesn't sound like any sound the car could make. like everyone has said here check your sound system blue tooth etc. and if the sound system is factory standard with no mods omg I'm lost.
Whenever my stereo powers up or powers off there is a beep beep its a sony, maybe there is some bad wiring behind the stereo that could be touching live power such as the memory wire to the accesories power input to the stereo, is the noise coming from your speakers or dash? long shot but could happen i guess.... good luck with it..
Did you work out exactly where the noise is coming from? Such as speakers or behind dash or something?
My only thought is with the stereo, if it's got an internal battery that's been going flat perhaps the beep is telling you what's the product number? If you narrow down precisely where the beep is coming from I'm sure we can figure it out