An exposure at SAR values of 6 W/kg causes a temperature increase in the head region of almost 1 ° C when using the exposure setup described above. Since the study is to be performed in a blinded way (neither the volunteer nor the directly involved scientist know the actual exposure situation) it is important to prove if the volunteers are able to perceive this warming. Therefore a pilot study was performed. It could be shown, that the volunteers are not able to recognize the actual temperature increase. Therefore, there is no risk of unblinding (the volunteers are not able to discover the specific exposure situation).