What the hell is that noise? The noise is hell.
A character within the story hears something odd. Unnatural. When they hear the sound once, it may not be that terrifying, but as time passes, they become more and more frightened. The sound gets scarier as it gains more and more relevance. Given time, the sound comes to haunt them, even away from the source. The sound has taken on a nightmarish relevance because of the setting. The sound could come from anywhere.
The trope isn't limited to a sentence, a catch phrase, or a song. The sound that terrifies the character can be made by the living, such as footsteps, a laugh, the call of a loud little animal. The sound may be made by the non-living, such as the creak of a chair, a door, a bouncing ball, the crackle of radio static, or any one of hundreds of other seemingly mundane noises.
This isn't a Brown Note, a sound or image that causes involuntary action/harm. This trope is about the psychological effect of a repeated noise to the character(s) in the story. 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.
- Children of an Elder God: In the prologue, two scientists and a team of spelunkers are exploring a network of caverns when they hear several faint, faraway screams. They freak out right away:
[There are faint screams in the distance]
Home Base (Speaker unidentified): What the hell was THAT?
- Quicken: When Emma goes nuts, she screams. Her scream sounds so scary and inhuman than her assailants step back.
A switch was suddenly flipped inside me. Something primal and inarticulate tore its way out of my throat, a sound I could have never imagined that I could make.
- SCP-682s roar.
- Lessons From The Mountain has Morgoth's laughter. Over five hundred years battling monsters, and Maedhros still considers his laughter to be the most frightful sound he has ever heard.
Maedhros: I proudly told him that he may kill me or torture me, but that would never be. He laughed. I think that was the most awful sound I have ever heard, and I have heard many things that no one should hear.
- In the song "Spooky Scary Skeletons" by Andrew Gold, the titular skeletons, despite being "shy" and "silly", are still considered scary because they "speak with such a screech", "shriek", and "shout startling shrilly screams".
- 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.
- Similar to Pan is the skinwalker of Navajo folklore. It initially freaks out its victim with two loud whistling noises that can be heard for miles. Its "speech" sounds like a distorted voice or animal call.
- A number of youkai are know to torment travelers by making sudden and terrifying noises, like the kerakera onna (a giant, ghostly woman who haunts brothel patrons with an Evil Laugh only her victim can hear), or Hachishaku-sama (Ms. Eight-Foot-Tall), who stalks young children and can imitate the voices of their loved ones but can only make a terrifying "po-po-po" sound otherwise.
- The Magnus Archives:
- The whistled tune that the narrator of "First Hunt" hears as he and his friend hunt portends something very bad. The tune is "A-hunting we shall go".
- In "Boatswain's Call" the mate on a modern ship carries the eponymous old-fashioned whistle. As the narrator finds herself in the midst of a disturbing trip in the (also strangely old-fashioned) lifeboat with the crew, the mate blows it, making a sound that is unnaturally and disturbingly shrill and piercing, yet somehow also sounds far away. Of course, this signals that things are about to go From Bad to Worse.
- Grisaia no Kajitsu: The clicking sound of Yumiko's boxcutter is something you learn to fear in Mihama Academy, as it indicates that it's wielder is royally pissed.