Characteristics of microwave-induced cochlear microphonics

Cochlear microphonics (CM) have been recorded from guinea pigs and from cats of differing body mass during irradiation by 918- and by 2450-MHz pulsed microwaves. Both horn applicators and a cylindrical waveguide exposure system were used to radiate the animals. The CM frequency and duration were similar irrespective of carrier frequency and mode of application. Parameters of the CM (except amplitude) were not influenced by orientation of the body axis to the electrical field or by pulse width of microwaves for pulses less than 30 μsec wide. The frequency of the CM correlated well with the longest dimension of the brain cavity and poorly with several dimensions of the head. Extrapolations of these animal findings to the human being indicates that the frequency of the microwave-induced CM in man should be between 7 and 10 kHz.