Microwave Hearing: Evidence for Thermoacoustic Auditory Stimulation by Pulsed Microwaves

Abstract

Acoustic transients can be thermally generated in water by pulsed microwave energy. The peak pressure level of these transients, measured within the audible frequency band as a function of the microwave pulse parameters, is adequate to explain the "clicks" heard by people exposed to microwave radiation.

Services to Operate and Maintain the Microwave Research Facility at Brooks Air Force Base, San Antonio, Texas

“…An intermediate acoustic mechanism may play a role in the phenomenon observed here through thermoelastic expansion caused by rapid temperature rise due to the microwave pulse [Foster and Finch, 1974;Borth and Cain, 1977;Lin, 1980;. It should be noted that the specific absorption per microwave pulse in our experiments, 20-50 J/kg, was at least three orders of magnitude larger than for microwave pulses known to elicit auditory sensations [Seaman and Lebovitz, 1989].…”

“…1982a, NCKP 1986. Foster and Finch [1974] showed both theoretically and experimentally in a physiological solution that microwave pulses could produce significant acoustic energy by thermal expansion from 5 * 10" 6 °C temperature rise in the solution from absorption of microwave pulses. It is generally accepted that the pulsed microwaveinduced audible sound is generated by a thermoelastic expansion of cranial tissue [Lin 1976, 1976a, 1976b, 1976c, Lin etal.…”

Pulsed microwave induced light, sound, and electrical discharge enhanced by a biopolymer

“…An intermediate acoustic mechanism may play a role in the phenomenon observed here through thermoelastic expansion caused by rapid temperature rise due to the microwave pulse [Foster and Finch, 1974;Borth and Cain, 1977;Lin, 1980;Chou et al, 1982]. It should be noted that the specific absorption per microwave pulse in our experiments, 20 -50 J/kg, was at least three orders of magnitude larger than for microwave pulses known to elicit auditory sensations [Seaman and Lebovitz, 1989].…”

Auditory response to pulsed radiofrequency energy

“…Gournay [1966] extended White's analysis to show that for single long pulses, the induced stress wave is a function of peak power density and, for shorter pulses, the stress wave is a function of the peak power density and pulse width (or energy density per pulse). Foster and Finch [1974] extended Gournay's analysis by conducting experiments in water and KCl solution exposed to RF pulses similar to those that produce sounds in humans. They showed both theoretically and experimentally that pressure changes would result from the absorption of RF pulses which could produce significant acoustic energy in the solution.…”

“…The hypothesis of Foster and Finch [1974] predicts that the RF hearing effect is related to thermoelastically induced mechanical vibrations in the head. Vibrations of this type can be produced by other means, such as by a laser pulse or by a pulsed piezoelectric crystal in contact with the skull which also induced cochlear microphonics in guinea pigs [Chou et al, 1976].…”