Researchers at Boston University have figured out how to block 94% noise with rings 3D printed from a mathematically modeled design.
The rings are called "acoustic meta-material," and work by catching a frequency, then sending it back to the source.
The researchers tested the design by putting attached one of their rings on one end of a PVC pip, and putting a speaker on the other side. when standing on the side with the ring, they heard nothing. A small amount of sound still comes through, but not enough to be audible by us humans.
This could eventually be useful for apartments and offices.
For more info, read Fast Company's article.