If you are hearing voices in your head while you ride the subway, you may not be so crazy after all.
Online video service Sky Go recently launched an ad that can speak directly to individuals as they rest their heads on subway windows.
Dubbed "The Talking Window," a transmitter fastened to the glass will emit high-frequency vibrations that are translated into a "voice" when a person leans against it.
The technology is known as "bone conduction" and will only be "audible" to a person leaning against the window.
Watch the video below to see exactly how "The Talking Window" works: