During the 1970s, home building picked up on the idea of a cheap but effective way to reduce sound travel from one floor to the next: popcorn ceilings. Essentially, after the drywall was installed, a finisher would come in with a plaster mix and spray on the ceiling drywall for a bit of a lumpy effect. The disparate clumps and bumps not only created a texture to an otherwise flat-looking ceiling, they also helped break up sound waves. After being spray-painted in white, the ceiling texture essentially blended with the rest of the room to produce a finished look. Popcorn…