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July 25, 2009 8:06 PM   Subscribe

What can I use to create a startling, loud, sharp noise?

I need to be able to conceal the source of the noise whilst in the presence of the person I wish to startle.
The noise needs to be louder than a cap gun (tried that).

In essence, the noise would need to penetrate an unguarded moment and engender an immediate state of 'startlement', a flinch.
posted by a non e mouse to Media & Arts (36 answers total) 2 users marked this as a favorite
In what kind of situation? Can you conceal things beforehand or do you need to conceal the device on your person?

I am told *cough* that an ordinary balloon full of LPG or propane will make a very dramatic exit when it is introduced to a cigarette lighter.
posted by localroger at 8:12 PM on July 25, 2009

clapping 2 pieces of 2x4 together is pretty loud, I suppose you could conceal them or just have them sitting innocuously somewhere ready for use.
posted by clanger at 8:16 PM on July 25, 2009

a mouse or rat trap? i only say this because i am dealing with mice right now and hearing a trap go off in the middle of the night is definitely startling. also they're easy to hide. just a thought...
posted by janepanic at 8:16 PM on July 25, 2009

Big sheet of metal. Have someone bang it. (You're going to have to figure out how to conceal it, if concealment is necessary.)
posted by ocherdraco at 8:16 PM on July 25, 2009

I can prepare it beforehand - I just need to ensure that the subject has no inkling of it.

That's not a bad idea - I'll have a go at that, but the balloon's presence may give it away a bit.
posted by a non e mouse at 8:18 PM on July 25, 2009

Whistle? I have been startled by a whistle on more than one occasion, and it is really easy to conceal.
posted by msali at 8:18 PM on July 25, 2009

These are great - keep them coming!
posted by a non e mouse at 8:19 PM on July 25, 2009

Air horn!
posted by so_necessary at 8:33 PM on July 25, 2009 [2 favorites]

Air horn, those things are really loud and small.
posted by Meatbomb at 8:37 PM on July 25, 2009

Seconding airhorn. It definitely startles the shit out of you. On the other hand at close range, especially used indoors, it can also cause hearing damage.

How about a starter pistol?

Or a firecracker.
posted by Netzapper at 8:39 PM on July 25, 2009

The noise needs to be louder than a cap gun (tried that).

Slightly related:

My school used to put on a haunted house of sorts, and one year there was an eXistenZ/The Game aspect to it: After the final room, you ended up in a lobby with a security guard, ostensibly waiting for your "I survived" certificate. It was planned out such that everyone but the last person would be called to the adjoining room right away. While the last person was waiting, another couple (actors, in reality) would walk in and wait on the other side of the room. After a few minutes, their conversation would start to get really heated, and would escalate to pushing and shoving. Right before the woman gets really pushed, the guard would walk over to intervene. He'd do the peaceful mediator thing - hand on the shoulder, quietly telling them to calm down. The guy would have no part of it. He pulls a gun, starts yelling, shoots the guard, and runs over to threaten and subsequently "shoot" the individual still waiting for their certificate.
30 seconds later, the doors open, and the whole group is standing around watching their friend freak out on CC television screens.

One night, it didn't quite work out. Everything went smoothly until the guard was supposed to get shot. For some reason, the cap gun jammed and wouldn't make any noise. The guard still collapsed, and in the heat of the moment, the mark didn't notice the odd silence of the situation. The thug runs over, and knowing the gun won't fire this last time, points the gun, pulls the trigger, and yells at the top of his lungs "RAT A TAT TAT!".

Based on his victim's reaction, you would have thought the gun fired an actual bullet.

Whats the moral here? Set the situation up right, and I don't care if you snap your fingers - they'll still have nightmares about it.
posted by niles at 8:41 PM on July 25, 2009 [12 favorites]

Dropping a textbook from chest height can make for a very satisfying snap.
posted by craven_morhead at 8:48 PM on July 25, 2009

posted by TimeDoctor at 8:55 PM on July 25, 2009

Snap-Pops thrown at the person in question's feet.
posted by banannafish at 9:07 PM on July 25, 2009 [1 favorite]

^ yeah I was going to say drop a large book from a significant height onto a hard floor. This is a great sound to scare the crap out of someone, especially if it is right behind them.
posted by @troy at 9:24 PM on July 25, 2009

Yep, an air horn would definitely do the trick. Check out a marine supply store or safety store.
posted by nelvana at 9:31 PM on July 25, 2009

Quickly and repeatedly bang the back of a large cooking pan or pot with a wooden spoon.
posted by Cool Papa Bell at 9:32 PM on July 25, 2009

the larynx.
I had a girlfriend who would startle hiccups out of me by suddenly and without warning go AHHHHHHUGgAGABUGGA!!!!!! and while it didn't make my hiccups go away, would utterly and completely terrify me every time.
posted by bottlebrushtree at 9:53 PM on July 25, 2009

If you are a chemist/have access to chemistry supplies, what you want is an Eppendorf tube and dry ice. Take a small chunk of dry ice. Place it in the Eppendorf tube. Click the tube shut.

Immediately afterwards, sidle up to your target's desk and sling it underneath. Stroll away.

As the dry ice turns into CO2, pressure will build up in the tube until, eventually, it explodes.

Naturally, this is provided as a purely theoretical exercise, and I am not responsible for any injuries which occur as a result of someone taking part in this highly entertaining and startling thought exercise.
posted by Comrade_robot at 10:15 PM on July 25, 2009

These paper noise-makers are pretty loud. And you can make them with whatever paper you've got lying around if you couldn't prepare ahead of time. We used to make these all the time when I was in middle school. It's just a folded piece of paper so it's pretty inconspicuous. Not sure if it's louder than a cap gun, but it won't take much to test it out.
posted by asras at 10:16 PM on July 25, 2009

Touchpaper is a prankster's best friend. I won't link to the recipe (think of the children!) but I can recommend it as 100% effective. You make a chemical solution and soak it up with blotter paper. When the paper has dried it will be imbued with a crystalline compound that explodes at the slightest touch, with a lot of light and sound. Try leaving a sheet under a doormat - BOOM!
posted by mhjb at 10:45 PM on July 25, 2009

Those little plastic champagne bottle noise makers you get on New Years would have the advantage of offering more decibles per square inch than about anything else on this list, and hey, they shoot streamers! They have definitely scarred the crap out of me more than once when they were popped behind me when I wasn't expecting it.
posted by slow graffiti at 10:50 PM on July 25, 2009

If you have a far enough drop onto a hard surface, rig up a string-based mechanism to release about 30 or 40 of those sperm-shaped popper firecrackers.
posted by crapmatic at 10:53 PM on July 25, 2009

Empty glass beer or wine bottles knocking together can be very loud. Your question also prompted me to google this:

Snapping Shrimp

May be hard to conceal though.
posted by evil_esto at 11:09 PM on July 25, 2009

Personal Defense Alarms fit in a pocket and shriek bloody murder at 120dB. Inexpensive as well. Plant anywhere and rig a line to pull the pin. Instant Sonic Landmine.

I myself have some experience with the Screaming Meanie and can testify that you are not ready for that kind of loud, even if you know exactly when it will go off. That gadget might be better suited for a small group that can be herded into a room-sized space at a known time, though.
posted by EnsignLunchmeat at 11:24 PM on July 25, 2009

Touchpaper is a prankster's best friend. I won't link to the recipe (think of the children!) but I can recommend it as 100% effective. You make a chemical solution and soak it up with blotter paper. When the paper has dried it will be imbued with a crystalline compound that explodes at the slightest touch, with a lot of light and sound. Try leaving a sheet under a doormat - BOOM!

There's always ammonium iodide.

Procure iodine crystals and pure ammonium (no detergent, etc.). Spread the crystals in a single layer on the bottom of a paper bowl. Cover in ammonium. Allow to stand for maybe ten or fifteen minutes.

Remove the crystals and allow to dry.

Once they're dry, this is one of the most pressure-sensitive explosives ever. You can set it off by poking it with a hair. It's not especially powerful, but I really don't recommend using more than about half a gram of it at a time.

Bonus: when it pops, it releases a cloud of beautiful purple smoke. Sometimes it even does miniature (3 inch tall) purple mushroom clouds!
posted by Netzapper at 11:33 PM on July 25, 2009 [2 favorites]

A shaken tin can or glass jar containing a handful of pennies?
Also, a different way to scare someone- an unexpected squirt from a water pistol?
posted by pseudostrabismus at 12:49 AM on July 26, 2009

It's very Brady Bunch, but get a big broad hardcover book, and practice dropping it so that it hits the ground flat. Very effective. Assumes you have a hardwood or concrete or similar floor, though.
posted by davejay at 12:51 AM on July 26, 2009

Empty can of Pringles. Put the lid on, step on it firmly. (Or jump on it.) Sound like a cannon going off.

Take a leather belt, make a loop and grab one side in each hand (no fingers on the inside!) put your hand together and pull them apart quickly and it will crack like a whip.

Practice your best Taxi whistle.

Small balloon filled with hydrogen + a match. (Not particularly safe, but make a hell of a boom.)

Starter's pistol. Much louder than a cap gun.

Drop a glass jar full of pennies. If the loudness doesn't get them to flinch, the sound of breaking glass will.
posted by Ookseer at 2:13 AM on July 26, 2009

Empty juice-box. Stamp on it. BOOM!
Also, I have a load of the "mini pillow" bubblewrap, you know the inflated bags about the size of your hand? They bang like a mofo as well, can also be hidden in a pocket and popped by clenching it in your fist. Even the quarter-sized bubblewrap is pretty loud and easily concealable. But really, juice-box!
posted by Iteki at 2:14 AM on July 26, 2009

Along the same lines as empty juice box (but easier to conceal), an empty crisp packet (er, chip packet?) with the open end placed facing you on your hand can be popped by bringing your other hand down on it sharply. There is a bit of a trick to it, you have to try and channel the trapped air towards the sealed end. It makes a suprisingly loud noise and is very quick to execute. When you get good you can move onto smaller wrappers like plastic chocolate bar wrappers.
posted by jzed at 3:14 AM on July 26, 2009

sperm-shaped popper firecrackers

posted by nosila at 7:01 AM on July 26, 2009

Please don't do this stuff near the person's ears. Hearing is nice to preserve.
posted by theora55 at 8:55 AM on July 26, 2009

Seconding theora55. As a sound engineer, I would also be QUITE pissed off should someone try this on me.
posted by Aquaman at 3:51 PM on July 26, 2009

Not the loudest thing on the list, but belt-snapping is highly convenient: fold a leather belt in half, holding the middle in one hand and the ends in the other. Bring your hands toward each other just enough to create a few inches space between the two layers of leather, then yank the belt taut, to slap the layers into each other. Yes, you must practice for optimal volume.
posted by aimedwander at 9:20 PM on July 26, 2009

Thanks everyone - I'm going to go with the air-horn initially and see if that has the desired effect - I'll work my way through the list if it doesn't.
posted by a non e mouse at 2:43 AM on July 30, 2009

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