As previously noted, the thresholds were obtained in a high ambient noise environment. This is an unusual situation as compared to obtaining thresholds of regular audio sound. One recent experimentation leads us to believe that, if the ambient noise level were not so high, these threshold fields strengths would be much lower. Since one purpose of this paper is to suggest experiments, it might be appropriate to theories as to what the rf sound threshold might be if we assumed that the subject is in an anechoic chamber. It is also assumed that there is no transducer noise. Given: As a threshold for the rf sound, a peak power density of 275 mw/cm2 determined in an ambient noise environment of 80 db. Earplugs attenuate the ambient noise 30 db. If: 1 mw/cm2 is set equal to o db, then 275 mw/cm2 is equal to 24 db. Then: We can reduce the rf energy 50 db to -26 db as we reduce the noise level energy from 50 db to o db. We found that -26 db rf energy is approximately 3 _u_w/cm2. Thus: If an anechoic room, rf sound could theoretically be induced by a peak power density of 3 _u_w/cm2 measured in free space. Since only 10% of this energy is likely to penetrate the skull, the human auditory system and a table radio may be one order of magnitude apart in sensitivity to rf energy. Up to Contents RF DETECTOR IN AUDITORY SYSTEM One possibility that seems to have been ruled out in our experimentation is that of a capacitor-type effect with the tympanic membrane and oval window acting as plates of a capacitor. It would seem possible that these membranes, acting as plates of a capacitor, could be set in motion by rf energy. There are, however, three points of evidence against this possibility. First, when one rotates a capacitor in an rf field, a rather marked change occurs in the capacitor as a function of its orientation in the field. When our subjects rotate or change the positions of their heads in the field, the loudness of the rf sound does not change appreciably. Second, the distance between these membranes is rather small, compared with the wavelengths used. As a third point, we found that one of our subjects who has otosclerosis heard the rf sound. Another possible location for the detecting mechanism is in the cochlea. We have explored this possibility with nerve-deaf people, but the results are inconclusive due to factors such as tinnitus. We are currently exploring this possibility with animal preparations. -40-