I don't know what's the name for this technique; it's used in most films and TV shows. I think it's done to create tension, shock or horror. I hear it when something bad happens, happened or is happening, mostly before camera transitions/cuts.
Basically a steady disturbing or unpleasant chord (not random or noise-like, maybe based on one note but mixed with similar yet conflicting notes) of high or low (not infra-sound or very low) notes; it somewhat gets louder but it doesn't escalate or change pitch. Usually lasts a few seconds then it stops all together/fades away.
I think they use string instruments, but I'm not an expert at music so I really don't know. Is there (hopefully) an official/unofficial name for this?
Here is an example: Evil Dead (2013) Soundtrack, example starts at 2:55-56; the video link starts at 2:52. Doesn't last very long, but should give you a good idea of the technique I'm talking about.