Microwave pulse-induced thermoelastic sensing: Toward understanding the microwave auditory effect

Microwave auditory effects, where high-frequency pulsed electromagnetic fields stimulate auditory perception, are believed to occur through thermoelastic waves induced in soft tissues of head and transmitted to the cochlea. This phenomenon can be understood as a sequence of physical processes: pulsed microwave irradiation and absorption → heat generation → elastic wave excitation. In this study, we propose a novel measurement framework called microwave pulse-induced elastic wave sensing, leveraging this thermoelastic conversion process. We constructed a shielded and soundproof measurement room capable of generating high-peak-power microwave pulses (up to 8000 V/m), and conducted irradiation experiments using dielectric phantoms. The resulting thermoelastic vibrations on the phantom surface were measured using a laser Doppler vibrometer, enabling quantitative analysis of the non-contact excitation mechanism. Additionally, we designed and preliminarily evaluated a head exposure system to investigate the applicability of this method to biomedical scenarios. This research introduces a new paradigm for microwave-based elastic wave measurement, offering a conceptual counterpart to photoacoustic sensing. [Work supported by Ministry of Internal Affairs and Communications (JPMI10001), Japan.]