A modulated physiological sensor is a noninvasive device responsive to a physiological reaction of a living being to an internal or external perturbation that propagates to a skin surface area. The modulated physiological sensor has a detector configured to generate a signal responsive to the physiological reaction. A modulator varies the coupling of the detector to the skin so as to at least intermittently maximize the detector signal. A monitor controls the modulator and receives an effectively amplified detector signal, which is processed to calculate a physiological parameter indicative of the physiological reaction.