[floam]

The recent National Academies study for the Department of State seemed to not think it is ultrasonic: https://federalnewsnetwork.com/wp-content/uploads/2021/04/Ha...

Some kind of pulsed RF/microwave seemed to be the most likely?

[thoughtstheseus]

Thank you for sharing this. It’s helpful to see that others have put substantial work into this problem.