"Targeting devices at a distance, they played music on an Amazon Echo, got Google Now to switch a phone to airplane mode, made Siri launch a FaceTime call, and even manipulated the navigation system in an Audi car, according to research presented at the Association for Computing Machinery’s annual Conference on Computer and Communications Security.
Using the same principle, Dr. Wu and Michigan’s Dr. Fu created an ultrasonic eavesdropping device that could be made to malfunction so that it produced some of the unusual noises reported by U.S. diplomatic personnel in Cuba. To design it, they analyzed sounds allegedly recorded during an incident and then made public by the Associated Press. During those incidents, people reported hearing a high-pitched whine or buffeting pressure akin to driving with the windows partly open. Others likened the sounds to chirping insects or metal dragging across a floor.
Under ordinary circumstances, almost no-one hears ultrasonic signals. But when two inaudible ultrasonic beams intersect, they can generate audible tones, at frequencies that could cause annoyance and pain, the scientists said."
https:// www.wsj.com/articles/can-ultrasonic-noise-make-you-sick-1529147100