Thermoacoustic sound generation in the head from high power pulsed microwaves, the microwave auditory effect or the Frey effect that people often hear as buzzes of clicks, may explain “anomalous” health incidents such as Havana syndrome. Directed energy weapons (DEWs) can exploit the Frey effect. This article explores the history and physical basis for the effect and estimates the magnitudes of peak acoustic pressures generated in the head and likely thresholds for adverse effects. The article concludes with discussion about whether thermoacoustic sound pressures generated in the head from high power pulsed microwaves might reasonably explain Havana Syndrome.