Have you ever been at the construction-site of a high-rise and experienced the sound-cocktail of machines, colliding materials, the blasting boom-boxes, shouting workers? And have you then returned to the same place years later; when the building is finished? Where are the echoes of these past sounds while you wait at the reception? What do you experience during an awkward elevator-ride? People with blank stares, no talking, maybe some music... but nothing, absolutely nothing audible from the past. Now have a closer look. See the scratches at the wall, maybe a sneaky footprint in the concrete behind an emergency-exit, a chipped wooden frame? Static traces from the past. Petrified life.
And now imagine a new construction-technique being introduced. Let some walls be written by massive 3D-printers, 'writing' threads of concrete layer by layer in quick scanning motion with preprogrammed perfection. All neat, all nice. And then modify the 3D-printer. You pick up the sound of the environment and send it to the nozzle of the printer. The sound acoustically modulates the thickness of the concrete-threads. The barely visible high-frequency modulation is similar to the modulated grooves in your beloved vinyl-records at home. Maybe a bit more pronounced. These ripples in the wall will persist once the concrete is dry and you could play back the record of past life with an appropriate scanner moving line by line across the wall and reading out the acoustic imprint.
Let's do it.
We will live in talking skyscrapers.