EM6: High pitched noise on headset

[Dries]

Whenever I use a headset (I tried different brands) with Earmaster 6, I hear a high pitched beep. My headset is on low volume (about 16%) but I noticed that the pitch changes when I raise the volume on my laptop.

Maybe it's my laptop what's the problem.
Does anyone else hear this? It gets annoying after a while..

Greets
Dries
Belgium