from Core77:

Using bone conduction, a technology developed for hearing devices, the “touched echo” installation in Dresdon transmits sounds of the cities devastating 1945 carpet bombing through the visitors arms when they rest their elbows on the balustrade and hold their ears. Several custom made sound conductors mounted to the railing send sounds of the airplanes and bombs exploding through vibrations, it’s completely silent unless you touch the rail.

More here.

Thanks Eric!