    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.

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