Frey effect

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The Frey effect ( English microwave auditory effect, microwave hearing effect, hearing RF ) is a phenomenon that high-performance near sources of pulsed high-frequency radiation occurs. Some people are able to reproducibly perceive pulsed high frequencies as clicking sounds without additional aids (such as radio receivers ).

A description of the effect was published in several articles by the American neurologist Allan H. Frey from 1961 onwards.

This phenomenon was discovered during World War II in people who were in close proximity to a powerful radar system .

Scientific research results

After the publication of the first data on the Frey effect, research was carried out into the causes and effects of the phenomenon. Possible applications for communication were also examined.

The Frey effect is now considered a scientifically generally recognized phenomenon without any pathological significance.

People who are sensitive to pulsed microwave or, more generally, high-frequency radiation describe the noises that occur as very quiet clicks that occur synchronously with the radiation and are only audible when there is silence. While it was initially assumed that only microwave radiation within the scope of the Frey effect was perceptible, it is now known that the frequency range in question is from 2.4 MHz to 10 GHz or from several 100 MHz to a few 10 GHz, depending on the source  extends.

Inner ear with cochlea (right)

The human cochlea ( snail ) in the inner ear is assumed to be the source of the stimulus . According to the currently favored thermoelastic expansion theory , there should be slight, impulse-like , heat-related expansion changes due to thermoelastic waves that conduct sound to the inner ear via bony structures . A direct interaction with the auditory nerve is excluded. A lower response threshold in the range of 16 ± 4 mJ in the frequency range 2.4 MHz to 170 MHz could be determined from studies on healthy test persons who were exposed to high-frequency fields  as part of magnetic resonance tomography at Philips . When positioned above the ears , the threshold dropped to 3 ± 0.6 mJ. Depending on the coil used, stimuli were typically determined at powers between 20 and 150 (± 50) W. The effect was most effective in the vicinity of the petrous bone . From the inner ear, the signals reach higher-level brain structures via the auditory pathway , just as is the case for purely acoustically triggered signals. The strength of the stimulus depends on the energy of the individual impulses. The frequency of the resulting sound is independent of the high frequency used, but shows a dependency on the dimensions of the human skull .

literature

  • Ronald L. Seaman, Robert M. Lebovitz: Auditory unit responses to single-pulse and twin-pulse microwave stimuli . In: Hearing Research . tape 26 , no. 1 , 1987, pp. 105-116 , doi : 10.1016 / 0378-5955 (87) 90039-6 .

proof

  1. ↑ AH Frey: Some effects on human subjects of ultra-high frequency radiation . In: The American Journal of Medical Electronics . tape 2 , 1963, p. 28-31 , PMID 13959628 .
  2. ^ Allan H. Frey: Human auditory system response to modulated electromagnetic energy . In: Journal of Applied Physiology . tape 17 , no. 4 , 1962, pp. 689-692 , PMID 13895081 .
  3. ^ AH Frey, others: Auditory system response to radio frequency energy. Technical note . In: Aerospace Medicine . tape 32 , 1961, pp. 1140-1142 , PMID 13895080 .
  4. ↑ a b c J. A. Elder, CK Chou: Auditory response to pulsed radiofrequency energy . In: Bioelectromagnetics . tape 24 , S6, 2003, pp. S162 – S173 , doi : 10.1002 / bem.10163 .
  5. ↑ a b Peter Röschmann: Human auditory system response to pulsed radiofrequency energy in RF coils for magnetic resonance at 2.4 to 170 MHz . In: Magnetic Resonance in Medicine . tape 21 , no. 2 , 1991, p. 197-215 , doi : 10.1002 / mrm.1910210205 .
  6. ↑ a b James C. Lin, Zhangwei Wang: Hearing of microwave pulses by humans and animals: effects, mechanism, and thresholds . In: Health Physics . tape 92 , no. 6 , 2007, p. 621-628 , doi : 10.1097 / 01.HP.0000250644.84530.e2 .