Instructables
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.
 
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Very good use of unusual materials to provide acoustics...... nice idea which has more applications than Halloween..... think security system. Can you imagine.....lol
darnduk1 year ago
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)  darnduk1 year ago
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.

Just in time for thanksgiving! :D I know some relatives that won't be overstaying their welcome this year!
Awesome project!
urant (author)  ClandestineIntestine1 year ago
hehe, just don't over do it or they may never come back!

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.
justjimAZ1 year ago
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)  justjimAZ1 year ago
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.
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)  justjimAZ1 year ago
So, you want to really scare someone?
Lots of someones. I hope it will work well enough to put it in a haunted house.
urant (author)  justjimAZ1 year ago
That's exactly what I build it for :D
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_Knowles1 year ago
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
gosphero1 year ago
Knew it would be cool just from the title.
urant (author)  gosphero1 year ago
:D
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)  stringstretcher1 year ago
Yes, you could absolutely do that.
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.
MikB1 year ago
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)  MikB1 year ago
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 urant1 year ago
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)  MikB1 year ago
Now, if only Adam or Jamie dropped an email, wow, that would make my decade :D:D:D
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)  licenseless1 year ago
Yes, it did :D
I just included the papers I have that document the psychoacustic response to infrasound. Enjoy !!!
ilpug1 year ago
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
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 Wizard1 year ago
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.
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 Bender1 year ago
Hi Satrek!
No, I used a cheap $15 one from Walmart. I'll go back and mention that in the parts list
urant (author)  urant1 year ago
Sorry, I meant yes, use the cheap ones, not the expensive ones.