Train window panes that whisper into your ears

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Tired commuters who were resting their heads against train windows in the Munich-North Rhine-Westphalia route in Germany were taken by a surprise when they heard a voice speaking inside their head. Later, they realised that the voice was an advertisement promoting Sky Deutschland’s new mobile app.
Dusseldorf-based advertising agency BBDO is using a combination of the concept and technology to allow individual commuters to hear an advert in a noisy train carriage.
It literally puts adverts straight into people’s skulls by using “bone conduction” — the transfer of sound to the inner ear through the bones of the skull — by sending high-frequency vibrations to windowpanes.
The messages can not be heard by the rest of the train passengers except the commuter whose head is in direct contact with the train’s window pane.