Thanks to my next-door neighbor, I can verify that this will effectively cover up the following noises: screeching, screaming, yelling, frustrated grunting, and loud sex.
This small sound machine is incredibly powerful, and has a variety of white noise sounds (pink, brown, white, and everything in between). It also has different fan noises. You can really blast the volume, too. I can't believe how much sound comes out of this little speaker. Ideally, you should put the speaker toward the source of the offensive noise and at least a few feet away from you. It's amazing, and worth every penny.