I don't think it is a "problem", I can make the noise you are describing on-cue with practically any vehicle, whether you can hear it depends on how quiet the car's cabin is and how much sound insulation material is between the cabin and the wheel wells.

I believe the sound is caused when the pads are basically in a position where they are losing grip with the disc and the sound is made by the disks rubbing partially against the pads without firm pressure contact.