What interesting BGM- was that the sound of puppies cringing?
So, you want to create a disturbing soundscape for a horror work that will properly unnerve the audience? Well, you could take the obvious route and put in dissonant chords, inhumanly deep organ music and Ominous Latin Chanting. Or you could try something more subtle. Certain distressing sounds, most often screams, sobs, and creepy laughter, played near the threshold of hearing, can subconciously set the audience on edge, making them feel that something is wrong, even if they can't place the source. To partially mask the noise, it will often be covered by loud background music of a more benign nature. The sound can become a Meaningful Background Event if it is diegetic, having an actual source somewhere in the story. Similarly, Fridge Horror can result if an ordinary noise results from a something scary. Sub-Trope of Hell Is That Noise.