Hell Is That Noise

""I don't know what that noise is, and I purposely avoided finding out. I like to think that it's Satan playing a vuvuzela in Hell.""

- The Distressed Watcher

What the hell is that noise? Hell is that noise.

Sometimes, sounds can be incredibly creepy. When you hear them the first time, they may not be that terrifying, but as time passes, they become more and more frightening as they gain more and more relevance. Given time, the sound comes to haunt you, even when you are not anywhere near the source. It doesn't just have to be a sentence, a catch phrase, a song, or even a laugh, it can also be a simple, mundane sound, like the creak of a chair, or a door, the sound of footsteps, the crackle of radio static, the call of a loud little animal, or any one of hundreds of seemingly mundane noises that suddenly take on a nightmarish relevance because of something you heard. This isn't a Brown Note, a sound or image that causes actual harm to a person in a story, but rather a completely mundane noise that, due to context, will terrify you in ways that cannot be described.

See also Hearing Voices, which can also be this depending on what kind of voices they are, and Nothing Is Scarier, which is almost the Visible Silence version of this. Sinister Scraping Sound is an intentional, psych-out type of hellish noise; if a noise foreshadowing a threat is produced by something attached to, or ingested by, that threat, it's The Croc Is Ticking.

Contrast Most Wonderful Sound, and compare and contrast Awesome Music.

Be cautious when adding Real Life examples; this is a YMMV Trope, and we don't need the Edit Wars.

Myth, Legend and Folklore

 * The Ur Example may very well come from Classical Mythology. The god Pan loved to scare the shit out of lonely travelers by hiding nearby and letting out a bloodcurdling scream. Ever wonder where we get the word "panic?" Now you know.
 * Pan was also pretty much the Glenn Quagmire of ancient Greece, except with the body of a goat from the waist down. So his cry didn't just sound horrible, it also warned people that they were going to get raped if they didn't run like hell.

Theatre

 * The shrill, piercing factory whistle in Stephen Sondheim's Sweeney Todd: The Demon Barber of Fleet Street is first used to make the audience jump and shut up in time for the opening number. Every subsequent use of the thing gets more and more hardcore - Sweeney's first kill, for instance - until the final use of the factory whistle coincides with . Yeah, you're still going to jump when you hear it on the soundtrack later.
 * And for those who haven't heard it, it's really shrill and piercing. If you're listening to it on your iPod with earbuds in, the sheer high-pitchedness of it will make you jump out of your skin no matter how many times you've heard it and how much you're expecting it.

Real Life

 * In Japan, the "Hells" ("Jigoku") is a term used for several groups of hot springs, including some found in the southern towns of Beppu and Unzen. In the latter, they are so called not only because of their extremely high temperature, but because the sound they make is said, in local folklore, to be the voices of the damned rising from the earth. You'd hope that it was just a figurative coincidence, but nope; the boiling alive of criminals and Christians during Japan's historical purges is well documented, and the screams of those unfortunate victims would certainly have been heard by nearby townspeople (not the least of which because the steam and fog the hot springs and the area's climate produce would help sound carry farther than normal).
 * For Amber Alerts, some locations signal it with this noise.
 * That US tone sounds like a movie's about to start. For true "Hell Is That Noise", you need the Canadian Amber Alert sound - strident, raucous, repetitive, and you can't opt out of getting the alerts.
 * If you've been to enough acquaintance's line of duty funerals, the song "Amazing Grace" and seven guns shot three times in succession can easily become this.
 * Air-raid and other sirens. They run them for civil-defense and other emergency drills from time to time in several places, including Russia, Israel, and some parts of the US (for instance, at 1:00 PM on the first Saturday of the month in Michigan).
 * Certain medical conditions make people specially prone o this trope. Hyperacusis is a hearing condition where the affected are extremely sensitive to certain sound frequencies to the point of actual pain, while Misophonia or Selective Sound Sensitivity Syndrome[ is a neurological disorder where the affected have overwhelmingly emotional reactions to otherwise innocuous sounds. To the sufferers of these conditions, even innocuous everyday sounds can become hellish.