Marginally on topic
Not so much animals attacking, as attacking them myself.

Apparently, if you get one of these old ultrasonic telly remotes from the Jurassic era 1980s, and press the buttons when there are moths fluttering around your outside light, they all drop down to the ground. It's supposed to be a defence mechanism against being eaten by bats.

I've always wanted to try this, but haven't yet been able to source an ultrasonic remote control and can't be arsed going to the trouble of building an ultrasonic generator to try out something that may actually be an urban legend.

So, does anyone know if this is true. And has anyone tried it? And does it work - because it would be great fun if it did!
( K2k6 has a proper job these days, Tue 29 Apr 2008, 15:33, 66 replies)

I'm not sure about the remotes
But I know it works if you jangle your keys really hard, as that makes some ultrasonic frequencies.
( Cawl, Tue 29 Apr 2008, 15:36, closed)

Oh go on
you know you just want an excuse to build an ultrasonic generator.
(Bazongaloid, Tue 29 Apr 2008, 15:37, closed)

^^ Would that just be
Some keys tied to a kid with ADHD?
Lots of keys :D
( Cawl, Tue 29 Apr 2008, 15:39, closed)

@al
Yeah, I know. But ultrasonic emitters require more specialised parts than my famously lethal high voltage supply. I can't really do a Scrapheap Challenge version. I'd need to spend money and order in some parts.

*thinks*

Actually now, wait a minute...if I stole got an old tweeter from a decent loudspeaker, that may go high enough....and building an oscillator is pretty easy using bits I've got lying around the lab....

*dons labcoat*
( K2k6 has a proper job these days, Tue 29 Apr 2008, 15:41, closed)

Next time you've got a remote
and you're standing near a fish tank, wiggle the remote at the fish, they can see the infra-red light and go a bit doolally.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 15:41, closed)

Mothra defense
It does work if yo uhave the right species of moth, but you have to be pretty close as the ultrasonic output of the old style remote controls was only good for about 2 meters. Used to test them to calibrate bat detectors.
(neurothing, Tue 29 Apr 2008, 15:41, closed)

Is the right species
likely to be one which I would find fluttering round my outside light in Eastern Scotland of a summer's evening?
( K2k6 has a proper job these days, Tue 29 Apr 2008, 15:42, closed)

If you're lucky...
en.wikipedia.org/wiki/Noctuid
( Cawl, Tue 29 Apr 2008, 15:45, closed)

Hey! If you're building oscillator circuits
design one for me, please? I want it to be able to produce from 10 to 30 Hz and have lotsa power to drive a home made speaker. (I'm playing with infrasound.) I'll want to either drive it with household current or with 12 V DC. Can you design me something I can build on the cheap?
( The Resident Loon Not a demographic. Do not measure., Tue 29 Apr 2008, 15:51, closed)

What's infrasound?
and what do you use it for?
(Bazongaloid, Tue 29 Apr 2008, 15:54, closed)

Nothing
What's a infrasound with you?

*shoots self*
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 16:01, closed)

@ Al
Making people see ghosts!
It's sounds that're too low to be heard by the human ear.

"Infrasound has been known to cause feelings of awe or fear in humans. Since it is not consciously perceived, it can make people feel vaguely that supernatural events are taking place."

en.wikipedia.org/wiki/Infrasound
( Cawl, Tue 29 Apr 2008, 16:01, closed)

@TRL
I'm not good enough with electronics to design my own new circuits, but it's pretty easy to find simple circuits in books or on the internet which you can use.

The most difficult parts of building a low frequency oscillator such as you require are the output transistors on the amplifier, which have to be pretty meaty to handle the powers required, and consequently the power supply. You're not going to get much out of a 12VDC supply - IIRC a single-ended amplifier will only provide about 4.5W rms into a 4Ω load. You can get up to about 25W rms using a Class B, FET based amplifier, but that is a little more expensive and complicated.

The easy way to do it is to buy yourself an old PA amplifier from a music shop, then build a little oscillator on stripboard. You can run the oscillator from batteries, and the components shouldn't cost very much. Plug it into the amplifier, and turn up the juice!
( K2k6 has a proper job these days, Tue 29 Apr 2008, 16:02, closed)

@Kaol
That wikipedia page on infrasound, 'sometimes infrasound is used in movies, such as Irreversible...'

Monica Belucci. I need say no more.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 16:13, closed)

Eh?
Should I see that film then?
( Cawl, Tue 29 Apr 2008, 16:15, closed)

La la la la la la la la la la la la la la la la
Kittens.




*Just to redress the balance.
( chickenlady b3ta's very own Elizabeth Taylor, Tue 29 Apr 2008, 16:16, closed)

what would happen
if you installed an infrasonic generator within a kitten? The world needs to know!
(Bazongaloid, Tue 29 Apr 2008, 16:21, closed)

@Kaol...Go and see it
if you like anal rape...
(Deskbound You insignificant speck of dust, Tue 29 Apr 2008, 16:21, closed)

@Deskbound
It's not something I'm a particular fan of, so I may give it a miss.
*prison flashback*

*shudders*
( Cawl, Tue 29 Apr 2008, 16:23, closed)

Hello chickenlady!
*waves*
Sorry about violating you and your man before, I won't do it again.

@Kaol I've never seen Irreversible, but I do love the Bellucci.

EDIT Unless it's a hardcore movie, how do they know that it's anal rape, other than the description on Wikipedia I mean? Does she say, 'Oh noes, please! Not up my bottom!' (in Italian, obviously. Bottomi!)
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 16:23, closed)

No bert, that would be silly
she goes "LOLZ, you gotz it up my poop chute! ROFL!"
(Bazongaloid, Tue 29 Apr 2008, 16:31, closed)

Irreversible
it's a horrible film, but is very well done. The nine minute real-time anal rape scene is not pleasant, as one might expect.
( crackhouseceilidhband Fuck off back to Mumsnet, Tue 29 Apr 2008, 16:32, closed)

@ The Resident Loon
I think if you want true infrasound, a standard bass driver (such as that you may find in a PA speaker or car sub) won't cut it - you'll need one of these 'Rotary Woofers'.
(Half of Stephen Fry's right buttock pissed on your dog on, Tue 29 Apr 2008, 16:35, closed)

It does sound pretty grim
Maybe I shouldn't watch it, I don't want my high expectations of the absolute stunner that is Bellucci to be ruined.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 16:36, closed)

^^ I don't like the first line...
"Want to hear what 5Hz sounds like?"

Surely the whole point is you can't hear 5Hz?
( Cawl, Tue 29 Apr 2008, 16:37, closed)

@Kaol
No, but you can certainly feel it. Apparently a certain very low frequency can make you shit yourself, it's called the 'Brown Note'.



And yes, I am fully aware that this has been proved to be bullshit on numerous occasions, but I'm still convinced that if you had a good enough speaker (one of those, for instance) it would be entirely possible to disrupt one's bowels.
(Half of Stephen Fry's right buttock pissed on your dog on, Tue 29 Apr 2008, 16:38, closed)

I reckon
interfacing an infrasonic generator with a small monkey or a goat would be interesting. Having said that Bert has probably already done it.
(Errorist, Tue 29 Apr 2008, 16:41, closed)

*shrugs*
I'm not convinced that you would shit yourself.

You'd need a frequency that would both loosen the anal sphinctor, and cause the muscles in the rectum to undergo a peristaltic (squeezing-a-tube-of-toothpaste-style) motion.
They're two different types of muscle, so are unlikely to have the same resonant frequency.

In my opinion.
( Cawl, Tue 29 Apr 2008, 16:43, closed)

@Errorist -I have
It was bazoo!!111!!eleventy!!one!oneoneleven!!!11

Vibrating goats and monkeys are the future.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 16:44, closed)

Would an infrasonic
monkey shit in the woods?
(Errorist, Tue 29 Apr 2008, 16:45, closed)

They tend to shit everywhere,
silently. But while filling all around them with a sense of awe and fear.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 16:46, closed)

Wow
That's pretty way out. Infrasonic monkeys sound amazing.
(Errorist, Tue 29 Apr 2008, 16:48, closed)

You can borrow mine if you like.
He's slightly used though, and only seems to vibrate like a monkey with parkinsons disease these days.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 16:49, closed)

@you two
Honestly, I make a valid scientific point, and you shit all over it like a pair of incontinent, scat-happy chimps.
( Cawl, Tue 29 Apr 2008, 16:51, closed)

Bert
are you sure you're not confusing your infrasonic monkey with the monkey with parkinsons that I lent you last week?
(Bazongaloid, Tue 29 Apr 2008, 16:51, closed)

Cheers Bert
Slightly used is fine. Might use some of the technical info above to jack its frequency up.
(Errorist, Tue 29 Apr 2008, 16:52, closed)

Tales of the Unexpected
I remember there was a story on Tales of the Unexpected back in the 80s where someone was imprisoned in a house - it was detached and away from roads - speakers were set up throughout and when activated they resonated at a frequency which was identical to that of human internal organs thus causing deadness (as it is known scientifically).


*Waves to Bert, despite violation.
*Applies cream to violation. Violate cream...Parma Violate cream.
( chickenlady b3ta's very own Elizabeth Taylor, Tue 29 Apr 2008, 16:52, closed)

D'oh!
*gets infrasonic monkey out of fridge*

I knew I'd left him somewhere!

@Kaol Ha! Yep, and we love it.

@chickenlady May I have some of your Parma Violate cream? I like them, they taste chalky.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 16:52, closed)

Actually...
I've never been able to understand why people say that you can't hear low frequencies, as you obviously can. If you drive a speaker with a 5hz square wave, it will go 'click' 5 times a second. Or am I missing something?
(Half of Stephen Fry's right buttock pissed on your dog on, Tue 29 Apr 2008, 16:53, closed)

Infrasound
Wikipedia has a pretty good article on the subject, so I'll recommend you look that up.

The Brown Noise is fantasy- it's based on hitting the resonant frequency of the abdominal cavity to make your intestines vibrate, thereby inducing intense shitting episodes. As no two abdomens are the same, the effectiveness of this is marginal at best.

What I have in mind is to make a half-wave rectifier (basically a large diode and a capacitor and a resistor), hook it up to a transformer to get some current at a low voltage, then run it through a large power transistor hooked up to an oscillator (basically a resistor and a capacitor), with a variable resistor (aka dimmer switch) to vary the frequency. I want to hit about 19Hz, ideally.

My plan is to make a fuck-off big electromagnet to run it through, and position it behind a nice big iron washer mounted to a sheet of rubber on an open cylinder (like a drum made from a piece of inner tube). I want to make very large amplitude waves with this.

Why?

So at Halloween time I can put it outside and scare the piss out of all the little kids on the street at once, without them knowing why they got scared.

Yes, I'm serious.
( The Resident Loon Not a demographic. Do not measure., Tue 29 Apr 2008, 16:54, closed)

Mr Loon
You are cruel.


I like it.



Bert - Parma Violets taste like perfume. *gags*


Where did that bacon on a string come from?
( chickenlady b3ta's very own Elizabeth Taylor, Tue 29 Apr 2008, 17:10, closed)

@RL
If you're down at those low frequencies and have an amplifier you can plug a sound output into, why not use an astable multivibrator (http://en.wikipedia.org/wiki/Multivibrator).

It'd give you an on-off pulse through an LED at whatever frequency you wanted, then you just check the voltage across one of the LEDs is a safe level for your amplifier, then solder on a stereo jack and plug it in! They'd not be any good for ultrasound, but for 5-30Hz I can't see any huge problems.

Tell us if you see ghosts, or gain mind-control abilities!

*Oh, you're just looking to scare kids. Ah, well.
( uberdeity Wondered why Owen Lars knew of the term "hell" on, Tue 29 Apr 2008, 17:12, closed)

Perfume has a distinctly bitter, alcoholic edge to it though
Parma violets are like chalky perfume.

Yum.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 17:12, closed)

I
may be being incredibly thick, and building an ultrasonic generator does sound amazing, but surely one of those silent dog whistles would just do the trick?
(Petite chien is going to do science to it, Tue 29 Apr 2008, 17:13, closed)

Have fun with that...
I'm off home to play GTA.
I'll catch you folk on Friday.
Bye!
( Cawl, Tue 29 Apr 2008, 17:25, closed)

Bye Kaol
Have fun stealing things and blowing things up in exactly the same manner as in the last game, only with slightly better graphics that you paid £50 for!

*waves*

*EDIT* @Little French Dog -I'm not too sure myself, but I reckon that's probably on the other end of the sound spectrum, as in too high, rather than too low.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 17:26, closed)

A multivibrator
is essentially what I was planning on building- a nice big capacitor with a variable resistor to modulate the output. It's a very simple oscillator. The challenge is going to be tuning it to the right frequency without an oscilloscope.

(Although actually I still know people at my engineering school, so I may be able to borrow one of theirs.)

I'd love to make it small and portable so I could carry it into a nightclub downtown on a Saturday night, set it in the corner and switch it on, then watch everyone go pale and sweaty and bolt out the door...

EDIT: @ 1/4 Stephen Fry's Butt: I have heard of those, but did you see the price they want for that thing? Ye gods!
( The Resident Loon Not a demographic. Do not measure., Tue 29 Apr 2008, 17:30, closed)

Bye Kaol!
Go and thump a granny for me on GTA - that's what I did the one time I played it...couldn't help myself. Then I went and hired a lady of the night....ahem.
( chickenlady b3ta's very own Elizabeth Taylor, Tue 29 Apr 2008, 17:30, closed)

Ta-ta chickenlady!
Ta-ta everybody!

See you all again for more crazy goat related capers tomorrow.
( Bert Monkeysex is waiting for the mods to delete him, Tue 29 Apr 2008, 17:32, closed)

Bye bye Bertie!
Lucky for you that you get to leave work and go home.

Freelance.
Work from home.
Never get to leave work.


But...can work in pyjamas!
( chickenlady b3ta's very own Elizabeth Taylor, Tue 29 Apr 2008, 17:34, closed)

you work from home
yet you bother to wear pyjamas?

I like to strip off as soon as the front door closes. I am presently naked apart from a strategic daffodil*

*may or may not be true
(Bazongaloid, Tue 29 Apr 2008, 17:47, closed)

@TRL
You've gotta get some sort of variably inductory thingy (technical term alert...) as the output and try to get that signal into the speakers of a packed club.
Brown note or not, if someone's got a few Hz at a ridiculous volume pumping through them, they ain't gonna feel too good for too long!
( uberdeity Wondered why Owen Lars knew of the term "hell" on, Tue 29 Apr 2008, 17:50, closed)

Geeks! ya gotta love em.
I can hear the whir of geeky brains as I sit here thinking of what to have for my dinner.
( girlinthehole, Tue 29 Apr 2008, 17:56, closed)

Mmmmmm
dinnner.

Will it be pork chops or will it be mince. decisions decisions.
(Bazongaloid, Tue 29 Apr 2008, 18:00, closed)

^^ Well I know it won't be curried goat.
I'm having prawns : )
( girlinthehole, Tue 29 Apr 2008, 18:02, closed)

Just goatse
Stick a lamp up your arse. Moths fly in and die from the smell. Always wanted to try this. There just aren't any moths round here :(
(The Archduke of South London I'm in your Girlfriend eating her organs, Tue 29 Apr 2008, 18:06, closed)

Actually
I have other plans for this thing as well. Aside from scaring children and making the Brown Noise, I want to play around with low frequency sound to make ripple patterns in water- I bet I can do all kinds of cool things with that! Imagine what the reflections would look like...

EDIT! Bwaahaahaa! See what happens when you work with other engineers? en.wikipedia.org/wiki/555_timer_IC

I'm told I can get an amplifier chip that will plug in and let me dump a LOT of power through it. And there are plans online for making powerful subwoofers...
( The Resident Loon Not a demographic. Do not measure., Tue 29 Apr 2008, 18:15, closed)

dinner
I had fish and chips for tea because it's a miserable rainy night that requires fish and chips.

I can also build yez a cheapo ultrasonic location system if yez want it, just to keep the post on topic.
( crackhouseceilidhband Fuck off back to Mumsnet, Tue 29 Apr 2008, 18:33, closed)

^^Post on topic?
What is this craziness you speak off?
( girlinthehole, Tue 29 Apr 2008, 18:59, closed)

seriously low
Most amplifiers will not be able to handle frequencies that low. It pains me to say this as an electrical engineer, but why not try a mechanical solution? Use an electric motor and attach an eccentric arm to it. Attach the other end to your rubber diaphragm and away you go. You'll probably need to gear it down with pulleys or some such to get the low enough speeds but it will be easier than mucking about trying to get an amplifier to work with very low frequencies.
( SteamedCleaner, Wed 30 Apr 2008, 1:49, closed)

^^^You want them to attach what
to their diaphragm...?
( Bert Monkeysex is waiting for the mods to delete him, Wed 30 Apr 2008, 9:22, closed)

@SteamedCleaner
He doesn't really need a normal audio amplifier, does he? I mean if he's generating a square wave he can just use a simple transistor/relay to control the flow of current through the speaker coil?
And if he put a properly designed LRC network network in the way wouldn't he then get a half decent approximation of a sine wave?

*is a little fuzzy on analogue stuff... shouldn't have drunk his way through uni...*
( uberdeity Wondered why Owen Lars knew of the term "hell" on, Wed 30 Apr 2008, 10:22, closed)

Surely
a square wave doesnt really count.. It would just be Speaker in, stop.. Speaker out, stop..
A sine wave would always be moving.

I would love to try infrasound, but have neither the patience or electroknowledge to make one, let me have a go on yours yea?
(Ahoyhoy, Wed 30 Apr 2008, 12:53, closed)

@uberdeity
You're probably right. It sounds like you paid more attention than me at uni, someone asked me about Ohm's Law the other week and I had to think about it for a wee while before I got it straight in my head. That's why I went for the mainly mechanical option, at least you can *see* if it's doing what it should.
( SteamedCleaner, Wed 30 Apr 2008, 17:55, closed)

Mechanical solution
That was my thought as well- until I multiplied 19 by 60 and realized that we were talking about 1200 rpm, which is pretty fast. The motor would make a lot of noise, as would the piston. My plan was to use a piece of truck inner tube for a sheet of rubber, stretch it over a cylinder, put a hook in the middle of it and use a connecting rod attached to a wheel a la locomotives to generate the sound, but there were too many parts that would make noise. Another engineer suggested using a ball instead of a diaphragm, as you wouldn't need to worry about its orientation inside the pipe, but I was still worried about noise. Besides, then you can't change the amplitude (volume).

What I have in mind is to make a square wave and use it to power an electromagnet behind a sheet of rubber with a large chunk of iron attached to the center. I'll want it to grab at the iron, then let it go, then grab and let go- the rubber sheet will be a LOT less responsive than a traditional paper speaker, so it will have more of a sine wave to it (I think). I may need to use a fish weighing scale to determine the k value (spring constant) for the rubber and see if I can get it to somewhere near a natural (resonant) frequency near 19 Hz, but then I may not bother. If I get mushy sine waves, so be it.

One of the engineers suggested using a timer chip (a 555 chip, to be precise) to do this. I think that will be what I try. He also said I can get an amplifier chip for less than a buck that will pump it up a lot- and if I need more than that I'll feed it through a MOSFET to pump out the power. (See Ampere's Law- I need current going through it to produce a good strong field, as well as a LOT of windings.)

I acquired today four chunks of 12" diameter PVC pipe, about 18" long, with junctions to fit over them to retain the rubber sheet. I need to find my breadboard to make the trial circuit, and once I get that figured out I'll make actual circuit boards for it and install rheostats and whatnot for control- and then see about getting some suitable iron for the electromagnet. I'll need something about 1/2" diameter bent into a C shape, with the ends of the C pretty close together. I may be able to get one of the machine shops in the area to do that for me.

I'll let you know what happens. This may take a couple of weeks.
( The Resident Loon Not a demographic. Do not measure., Thu 1 May 2008, 2:30, closed)

My mate's band
is called The Infrasound.

Check 'em out on MySpazz
( Monty Boyce, My cheese game is strong, Thu 1 May 2008, 13:35, closed)