THRESHOLDS OF MICROWAVE-EVOKED WARMTH SENSATIONS IN HUMAN SKIN

We measured thresholds for microwave-evoked skin sensations of warmth at frequencies of 2.45, 7.5, 10, 35, and 94 GHz. In the same subjects, thresholds of warmth evoked by infrared radiation (IR) were also meas ured for comparison. Detection thresholds were measured on the skin in the middle of the back in 15 adult male human subjects at all microwa ve (MW) frequencies and with IR. Long duration (10-s), large area (327 -cm(2)) stimuli were used to minimize any differential effects of temp oral or spatial summation. Sensitivity increased monotonically with fr equency throughout the range of microwave frequencies tested. The thre shold at 94 GHz (4.5 +/- 0.6 mW/cm(2)) was more than an order of magni tude less than at 2.45 GHz (63.1 +/- 6.7 mW/cm(2)), and it was compara ble to the threshold for IR (5.34 +/- 1.07 mW/cm(2)). (C) 1997 Wiley-L iss, Inc.