Karhunen basically has latin pronounciation. Adapted for english it's sharp 'k' (no 'h' sound in it), short 'a', sharp 'r' and short 'e'.
Kar is like comedy-Irish pronounciation of Car but as said with sharp 'k' and short 'a' and sharp 'r'. The 'u' is like 'ou' in You but shorter. Nen is like 'ne' in Network with an additional 'n'. After putting these pieces together try to pronounce it as fast as you can and you're pretty close