Introduction: The Psychoacoustic Bucket From Hell

Picture of The Psychoacoustic Bucket From Hell

Hi!!

What is this you are probably asking yourself from the title  (and the fact that the bucket in question looks just plain normal) ?
Most certainly, you were expecting some kind of mega Halloween hell bound caldron or at least a mean looking trick or treat bucket that produced some kind of light show.

Well, kind of.

This is without doubt, one of the scariest props that you can build, not because it in itself is scary, but because it will induce anxiety, uneasiness, fear, chills down the spine in about 30% of the people who are in the same room as the bucket.  

Yeah, right.....

How does it do that?

Well, with...

Science!!!

Inside the lid of this bucket is a DIY infrasound driver that can produce high pressure sound waves up to some 18hz.

From Wikipedia:

Psychoacoustics is the scientific study of sound perception. More specifically, it is the branch of science studying the psychological and physiological responses associated with sound (including speech and music). It can be further categorized as a branch of psychophysics

It turns out that while we can't actually hear infrasound, we can still feel it, and some frequencies cause some odd (and some creepy)  reactions to our body.

For example, 4hz very high pressure transducers are banded from sales, because at 4hz, the air in our lungs starts to resonate and you can't breath.

Some people experience nausea at 10hz.

And some, about 30% according to some of the only papers I have found of the subject, feel afraid or  "a presence" at around 17Hz.

Between 17hz and 18hz some people's eyes start to resonate, and a slight visual hallucination is produced, like the light you see if you press you eyes with your fingers.

This, combined with the strange unease and your killer Halloween murder ghost story, and you will have some very scared guests.

If you're curios, and want to know more about the science behind this phenomena, download the papers included in this Instructable.

Now, this actually took some 6 months of research to come up with, while the build in itself will take only some 6 hrs.

The first build question is the most obvious: Why not use a subwoofer and amp?

Well.....it turns out that few woofers can go safely down to 15hz, and they are EXPENSIVE. Add to that an amp capable of driving it, and you are looking at close to $500 specially if you need (as we do) high sound pressure levels.

ouch... back to the drawing board.

Next I researched into subsonic whistles (driven by compressed air) but the tube length needed made it both expensive and impractical.   

I finally came to an old sub woofer design called the ServoDrive, that used a servomotor coupled to the cones.
This was perfect since the old ServoDrives were close to 80% efficiency due to the servomotor's high efficiency (95%) and the direct mechanical coupling.

And I could cheaply build a simple single frequency version.

Something I learned while doing this project is how inefficient voice coil speakers are. Most commercial woofers are 1% to 2% efficient, meaning that the 300 watt woofer and amp are giving you some 3 to 6 watts of equivalent sound level pressure  (over simplified but its close) 

I'm feeding my driver some 20watts (at 50% efficiency) so maybe I builded the equivalent of a 500 to 1000 watt woofer and amp.  

Now, my design is  limited to a single output frequency.

Step 1: What You Need

Picture of What You Need
You will need:

Parts:
  • One plastic 19L bucket (I bought mine at HomeDepot, so it would be a Halloween orange :D )
  • One cheap 12 volt car portable air compressor (that you will destroy)
  • Some scrap plywood strips
  • JB Weld or Liquid Nails
  • 4 wood screws
  • 1 wire hanger
  • Variable DC power supply
Tools:
  • Handsaw
  • Screwdriver
  • Pliers.

Step 2: Prepare the Lid

Picture of Prepare the Lid

Saw a hole in the bucket lid one inch from the inside lip.

Save the left over, since it will be your "cone"

Step 3: Disasemble Air Compresor.

Picture of Disasemble Air Compresor.

Once you remove all the screws from your pump housing, you will find something very much like what you see in the picture; a motor plus cylinder.

Remove the cylinder, and the piston head, so you are left with the motor, the crank and the piston arm (like in the last pic)

Step 4: Start Building the Spider.

Picture of Start Building the Spider.

Use the plywood scraps to build the spider that will hold the motor and crank.
The piston arm must be dead center in the lid. Use little plywood blocks to lift the spider 1" to 1.5" from the lid bottom so that your "cone" will move only on the inside of the lid.

Now be careful with the blocks, since they must be parallel to each other. (see pic and next steps)

Step 5: The "cone"

Picture of The "cone"

I glued some plywood to the leftover lid to give it rigidity.
The distance between the two parallel sticks is the same as the thickness of the spider legs (the small plywood blocks). This is important because I glued some bits of wire hanger on the sides that inhibit the cone from spinning inside the spider. Please see next step so this will be clearer .

Step 6: Assemble the Driver.

Picture of Assemble the Driver.

Drill a hole dead center in the cone.

Attach a piece of 4" wire hanger to the piston arm.

Place the cone inside the lid as in the picture. The parallel pieces of plywood on the cone will line up to the spider's wood blocks. Glue the 2" pieces of wire hanger to the cone´s plywood. This will avoid the cone from moving sideways.

Turn the driver upside down and clip the extra wire coming from the piston arm, fold it and glue it.

Drill a small hole in the lid and pass the motor's wires to the other side of the lid.
Place a screw through the lid in each of the spider's blocks to firmly secure them in place (see picture)


Place driver on bucket.

Step 7: Turn It on and Calibrate.

Picture of Turn It on and Calibrate.

Since room acoustics are really important in sub sonic drivers, I put the bucket, a variable DC power supply and myself into a small bathroom and closed the door and bathroom window.

I hooked up the bucket to the DC power supply and started to experiment with different voltage settings.

Since the DC voltage is more or less proportional to motor speed, the higher the voltage, the higher to output frequency.

At 2 volts, the prototype driver is not completely noiseless, as the motor makes noise and the cone rubbing the sides, but it really moves air!!

At 6.1 volts, I had to turn it off, as I got really nauseated.

At 9.4 volts, Success!! I managed to creep myself out!! I could "feel" someone in there with me, it was a really odd sensation, not pleasant at all and even tough I knew what was going on, the creepy factor was there.

I can´t wait for Halloween next year!!

Note:
If you don't want to keep your DC power supply connected to the bucket, you can use a DC power wall supply and the appropriate resistor network to supply the correct voltage, or if your a bit handy in the electronics department, build a regulated DC power supply using a LM317 or similar.  


 

Comments

KyrtinA (author)2015-12-13

This is definitely one of the more innovative ideas I've come across for infrasonics. I've had a few ideas for new infrasonic speaker designs occur to me in my research, but finding a capable engineer who can put them to the test has been the challenge for me. What I'd really like to design is a mobile infrasonic system compact enough to be worn. There are a lot of documented positive effects besides all of the strange ones when you manage to hit the right frequencies and Decibel levels, but most of the equipment has to be custom built.

ke7ofi (author)2015-09-29

Did you try it in larger rooms? Would the perceived intensity be inversely correlated with room volume?

newbeatle (author)2015-04-12

so interesting not for a creeping experience intead a way to make subsonic sounds. i have a question about the motor , which kind of power supply you have used ? and how do you make to avoid or eliinate the noise of the motor? i know that you use low RPM and so there is no much noise as when you drive it at a normal speed , but how do you make it spin quietly ? regards from mexico

urant (author)newbeatle2015-04-13

Hi,
I used a desktop 12VDC power supply. Since the motor is DC, it makes virtually no noise.
Now, if you want to dig a little deeper, it turns out that some of the first commercially avaliable high power sub woofers actually used servo motors as the "moving coil" in the set up. They were expensive, big and required a lot of maintenance, so when solid state amps went down in price enough to be cheaper, those old servo subs went away. I actually know someone who worked in a club that had one, and he told me that they had so much power that it would rattle his teeth. You can find a lot of material on them on the web, and looking at them might give you ideas on how to build a modern version.

ke7ofi (author)urant2015-09-29

Does “desktop” mean desktop PC, or is that just the size? I don’t understand how I’d adjust the voltage coming out of a PC power supply, but it would definitely be cheaper to salvage.

holland1115 (author)2013-06-15

Very good use of unusual materials to provide acoustics...... nice idea which has more applications than Halloween..... think security system. Can you imagine.....lol

darnduk (author)2012-11-23

I'll bet it'll run some wildlife off too. If I took this hunting and controlled it remotely could I drive the deer to me? I wonderrrrrrrrrrr.

urant (author)darnduk2012-11-26

Wow, that's a really interesting idea.
What I do know, is that wildlife does respond to subsonic sound. The classic example is of animals disappearing before an earthquake or tsunami hits. Apparently they hear/feel the subsonic rumble and RUN.
If you do try it, please tell us your results.

ClandestineIntestine (author)2012-11-20

Just in time for thanksgiving! :D I know some relatives that won't be overstaying their welcome this year!
Awesome project!

hehe, just don't over do it or they may never come back!

Jim_Knowles (author)2012-11-16

Thanks for uploading the pdf's, I was able to download with no problem.

I'm surprised that the movie theaters don't use a version of this to make scary movies even more spooky. Or maybe they do???

Thanks again for a great 'ible.

justjimAZ (author)2012-11-11

Sweet. I was planning to build a huge "whistle" to produce the ultra low tone. This will be so much easier to make and store.
I understand 16hz causes vomiting, though. Don't want to get there.

urant (author)justjimAZ2012-11-15

Can you say what you are planning to use the whistle for?
If you want, you can alter the construction a bit by using an old blown out sub. Just get rid of the magnet and glue the piston shaft directly to the cone. This will reduce the non sub sonic mechanical noise.

justjimAZ (author)urant2012-11-15

I was going to use it in just the same way you are using this. In effect, I was making a "one note pipe organ", but this seems MUCH better!

urant (author)justjimAZ2012-11-16

So, you want to really scare someone?

justjimAZ (author)urant2012-11-16

Lots of someones. I hope it will work well enough to put it in a haunted house.

urant (author)justjimAZ2012-11-16

That's exactly what I build it for :D

Jim_Knowles (author)2012-11-16

Excellent Instructable! I have two questions. One, exactly what did you use for your DC power supply? And two, why is it I seem to be unable to get two of the four files you reference? The file Infrasonic Release and the file Infrasonic Results both give me a 403 error; it says 403 Forbidden Request forbidden by administrative rules. The other two downloaded fine.

Thanks for this great idea; I will build one of these!

urant (author)Jim_Knowles2012-11-16

Thank you!
I used an old HP variable DC bench top variable power supply that I've had for years (0-50V, 0-5A)
I don't know, so I erased the .doc and uploaded some pdf

gosphero (author)2012-11-13

Knew it would be cool just from the title.

urant (author)gosphero2012-11-15

:D

stringstretcher (author)2012-11-14

Can you use an Arduino's PWM output to control the motor speed. You could use higher voltage, which equals more power, yet run it as slowly as you wish. I have experienced these feelings of "creepiness" in a parking garage in town. The exhaust fans turn very slowly, and the resulting air waves make me feel nauseous. No one else seems to hear them! funny thing is I wear hearing aids... and can't hear well otherwise.

urant (author)stringstretcher2012-11-15

Yes, you could absolutely do that.

Yard Sale Dale (author)2012-11-14

Brown noise....... interesting instructable. Surely there are uses for it beyond halloween. I have put car speakers in buckets before just to play with. It sounded cool with heavy metal, harsh and with a lot of bass.

MikB (author)2012-11-10

Ohh ... and to think Mythbusters just recently spent a fortune on amps and speakers to test this one out, when all they needed was a bucket! Oh dear :)

urant (author)MikB2012-11-10

Well, the difference is they did it outside. You need a lot more power in open air. That's why I tested the bucket in a small, enclosed room.

MikB (author)urant2012-11-10

Yeah, I know, I'm just saying, I bet they'd be annoyed if they found someone with a bucket and aircompressor outdid them!

urant (author)MikB2012-11-10

Now, if only Adam or Jamie dropped an email, wow, that would make my decade :D:D:D

licenseless (author)2012-11-09

so... did it work? I want to hear more peoples reactions on this thing... its sounds AMAZING!!! if more people had the reaction or if you could post some of the links to the publications where you researched this ... That would be awesome!!! even if it only worked on a couple of people that is cool enough hahahahahah awesome idea man!!!

urant (author)licenseless2012-11-09

Yes, it did :D
I just included the papers I have that document the psychoacustic response to infrasound. Enjoy !!!

ilpug (author)2012-11-08

I love finding cool projects like this when I have all the stuff lying around to build it.

Will do this when get home from college

Lectric Wizard (author)2012-11-08

Great idea to use the compressor. You could also use a stepper motor & driver to get really accurate frequencies,but at more $$$.

urant (author)Lectric Wizard2012-11-08

Hi!

Yes, you could use a stepper, but since it's a single frequency woofer, it would be a little overkill, buuuttttt, if you modulate the input, then you would build a modern ServoDrive woofer.

Dominic Bender (author)2012-11-08

I have to make one of those for our roleplayng group! Thanks for sharing such a detailed instructable!

Apologies for posting again - this question came to me just after I posted. Regarding the compressor, I'm seeing quite a few that are meant to be used to inflate foodballs and the like - will they suffice, or war the one you used intended for more heavy duty use?

urant (author)Dominic Bender2012-11-08

Hi Satrek!
No, I used a cheap $15 one from Walmart. I'll go back and mention that in the parts list

urant (author)urant2012-11-08

Sorry, I meant yes, use the cheap ones, not the expensive ones.

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Bio: A tinker since the cradle, I love looking at things and trying to figure out how they work and the best way to mod them
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