iPad Air - background noise in recorded videos or voice memos

Hello,

on my new iPad Air Wi-Fi 64 GB, all recorded videos or voice memos shows an unusual background noise. I do not mean the well knwon "white noise" in the background of videos, recorded in very quiet environment! It´s more like wind noise, which is well known in videos taken outside in windy conditions without microphone protection. But I get such a noise in dead calm conditions. It´s definitely not caused by my breath or my fingertips (which are far away from the microphones), holding the device. The noise isn´t constant either, it pop´s up sporadically, but in every video.

I can´t hear this "wind noise" on my wife´s iPad mini.

Any suggestions? Anybody observed this on his iPad Air, too?