As unique as this idea is, it could be mildly irritating after a while. A Scottish company, Harris Hynd Ltd. has developed a technology whereby the entire billboard is a loudspeaker. What's interesting is that there are no speakers involved. The technology enables cardboard, foam, or glass to resonate thus creating the sound. These boards can be programmed with any form of audio that is triggered by an infrared sensor.
Interesting. But not if you have 30 of them yacking at you as you walk through the airport. Again, we shall see how the technology is accepted. Stories on the topic: