I don't know if this is a hidden feature or if my X5 was just bugging out.

My wife's cellphone was charging and it was connected to jack behind the center console... right were the rear passenger vents and heated seats are. Right before my wife's phone got the ringing sound of her text message, I over heard this "dadaduuuummm" (3 x's) sound like thing over the bmw speakers/sound system. The sound would only happen once before she recieved her text message. She recieved 2 text messages and oddly it happened twice. Of course this only happened when her phone was charging through the jack?