I’ve mentioned these kinds of stories before – the latest mad scientist device that can beam advertising, propaganda, etc. as a beam of sound to a hapless citizen. Only the tech is far enough along that you can schedule an appointment and have it demonstrated to you. From International Robotics’ propaganda:
International Robotics is proud to demonstrate the impossible by remotely transmitting tightly focused sound waves, aimed specifically at any object, sculpture, wall, ceiling, floor and other surfaces, including one or more people. The Hypersonic Sound Waves travel silently through space, up to 300 feet away, then convert into an instant sound source whatever surface they impact. Amazingly, if you aim this magical device at a person, their head will become a speaker, and they will hear your message “inside” their head.