military accent
A military accent is the accent of one who is raised in a family that has been redeployed often. The fact that one has gone to school from a very young age with others from various regions (i.e. New York, Texas, Minnesota, California), causes all those accents to merge into one that is not easily identified, but noticeably different to one who has lived in a single region their whole life.
Kalina couldn't quite identify why Mike sounded different, until she realized it was the military accent he picked up in Germany and Italy.