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Microwave Hearing: Evidence for Thermoacoustic Auditory Stimulation by Pulsed Microwaves

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H. H. Seliger, W. L. Bigelow, J. P. Hamman, Kenneth R. Foster, Edward D. Finch · 1974

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Pulsed microwaves can create audible sounds in the human head without heating tissue, proving non-thermal biological effects exist.

Plain English Summary

Summary written for general audiences

Researchers exposed people to pulsed microwave radiation and discovered they could hear 'clicks' synchronized with each pulse, even when the exposure was too brief to cause detectable tissue heating. The study demonstrated that microwaves create acoustic pressure waves in water through rapid thermal expansion, explaining this unique auditory phenomenon.

Why This Matters

This 1974 study documented something remarkable: the human body can directly perceive microwave radiation as sound through a mechanism called the thermoacoustic effect. When pulsed microwaves hit tissue containing water, they create tiny pressure waves that the inner ear detects as clicks or buzzing sounds. What makes this finding particularly significant is that it occurs at power levels (0.5 to 5 watts per square centimeter) and pulse durations (50 microseconds) that don't cause measurable heating. This challenges the long-held assumption that all biological effects of EMF require tissue heating. While modern devices like cell phones and WiFi routers typically operate at much lower power levels and use different pulse patterns, this research established a clear biological interaction pathway between microwave radiation and the nervous system that doesn't depend on thermal effects.

Exposure Information

Specific exposure levels were not quantified in this study.

Cite This Study
H. H. Seliger, W. L. Bigelow, J. P. Hamman, Kenneth R. Foster, Edward D. Finch (1974). Microwave Hearing: Evidence for Thermoacoustic Auditory Stimulation by Pulsed Microwaves.
Show BibTeX
@article{microwave_hearing_evidence_for_thermoacoustic_auditory_stimulation_by_pulsed_mic_g7384,
  author = {H. H. Seliger and W. L. Bigelow and J. P. Hamman and Kenneth R. Foster and Edward D. Finch},
  title = {Microwave Hearing: Evidence for Thermoacoustic Auditory Stimulation by Pulsed Microwaves},
  year = {1974},
  
  
}

Quick Questions About This Study

Yes, people exposed to pulsed microwaves at 0.5 to 5 watts per square centimeter can hear synchronized 'clicks' with each pulse. The effect occurs through thermoacoustic pressure waves generated in tissue water, not through electromagnetic interference with hearing aids or electronics.
The study found that microwave pulses need to be moderately intense, typically between 0.5 to 5 watts per square centimeter incident on the head surface. Below this threshold, the thermoacoustic pressure waves aren't strong enough to stimulate the auditory system.
No, pulses of 50 microseconds or less cause virtually no temperature increase (less than one millionth of a degree Celsius). This makes microwave hearing the only confirmed biological effect of microwave radiation that occurs without observable tissue heating.
Pulsed microwave energy causes rapid thermal expansion in water, generating acoustic pressure transients within the audible frequency range. The researchers measured these pressure waves directly in water samples, confirming the thermoacoustic mechanism behind the hearing phenomenon.
This phenomenon proves that microwave radiation can have biological effects without heating tissue, challenging the thermal-only safety standards. It demonstrates a direct interaction between electromagnetic fields and the nervous system through non-thermal mechanisms that warrant further investigation.