The human senses (above all, that of hearing) do not possess one set of constant parameters, to be measured independently, one at a time. It is even questionable whether the various 'senses' are to be regarded as separate, independent detectors. The human organism is one integrated whole, stimulated into response by physical signals; it is not to be thought of as a box, carrying various independent pairs of terminals labeled 'ears', 'eyes', 'nose', et cetera.