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The Mathematics of Sex Toys...

...in which we learn just how big a stinker Franklin is.

Okay. So. Long story behind it, but I have on my balcony a large Tupperware container filled with sex toys. Vibrating eggs, to be exact. At one point, I had about 250 of them. I keep giving them away to people (in fact, I've been known to refuse to let guests leave the house unless they take one with them), and now I'm down to about 20.

Which is still a lot of vibrators, just for the record.

Some time ago, I read online about a guy who'd taken a vibrator and connected it to a Basic Stamp--think "little tiny computer on a single chip"--that he had programmed to switch the vibrator on and off at random intervals. The idea, you see, was to play with a quirk of human physiology.

Quick dissertation about human anatomy: The way our sensory nerves work, if you present the same stimulus to the same part of the body without varying it, eventually, your sensory nerves will quit responding to it. Take a toothpick and put it on your palm; you'll be able to feel it. Leave it there long enough without moving it or your hand and eventually you'll stop feeling it.

The sexual organs are no different than any other organ in this regard. Flip side of the same coin, if you vary the stimulation presented to a sensory nerve, it'll keep informing your brain "Hey! The stimulus has changed!" and you won't be able to ignore it.

Now, this guy had programmed his Basic Stamp to switch a vibrator on and off at random, but fairly short, intervals. The idea was to create an infuriating sex toy--a sex toy that, when you wear it, you absolutely can not ignore. Because the stimulation is random, you don't become acclimatized to it--and if it switches on and off quickly enough, it also doesn't stay on long enough to get you off. So basically, he created a sex toy that will make sure you always pay attention to it but won't make you come.

If you draw a graph of the way the sex toyy switches on and off, you get something like this:

There's vibration, then no vibration, then vibration, then no vibration, for randomly varying periods of time:
bzzzzz....bzz.........bzzzzzzzzzz..bzzz......bzzzzz... you get the idea.

Now, that's good and all, but the vibrators I have are equipped with a little thumbwheel speed control. When one of my partners is foolish enough to put me in charge of the control pack for one of these things, I like to run my thumb up and down the speed wheel thingy, making the vibrator go FASTER and slower and FASTER and slower.

So I started thinking, why not program a computer to run the vibrator for random times at random speeds? From there, I started thinking about how to actually code for that.

Now, it seemed to me, as I was thinking about it on the bus on my way down to Tallahassee, that the most obvious way to go about this is to take a bunch of sine waves and put them together. One can construct a waveform of nearly arbitrary complexity by merging together sine waves of different frequencies, via a mathematical bit of wizardry called a fast Fourier transform.

For example, suppose we have something like this:

The sum of the red sine wave and the blue wave (which is itself a composite of three sine waves) looks a bit like this:

Now, feed that into a vibrator and it should keep a person infuriatingly close to orgasm without letting her get off or ignore the vibrator just about indefinitely.

The thing is, you want a wave that looks random. Any composite of a finite number of sine waves will be periodic (that is, at some point it will start to repeat), so you want something that looks random and also has a long periodicity. I was thinking about how to choose a relatively small number of sine waves--say, sixteen or so--in such a way as to maximize the periodicity and also maximize the apparent randomness when combining them with an FFT. Make the ratios of their periods prime? Stuff like that?

I was hampered somewhat by the fact that I also know fuck-all about how to actually do an FFT, too, which means that basically I know squat about the best way to go about choosing the sine waves.

Shelly's dating a physicist, though. And he took one look at the problem and observed that a fast Fourier transform isn't really necessary; it's using an anti-aircraft cannon on a mosquito.

His idea, which is brilliant, is this:

Take a sine wave whose period is the interval of time over which you don't want the pattern of the vibrator to repeat. Add it to itself with a period of double that, and add it to itself with a period of three times that, and again with a period of five times that. (Geeky readers will already see where this is going: 1, 1, 2, 3, 5... is the Fibonacci sequence.)

You don't need very many sine waves to get a right royal (and therefore random-looking) mess.

So, in theory, it will be remarkably simple to make The World's Most Annoying Sex Toy(tm). A little bit of simple programming and some kind of variable interface and the result should be a vibrator that will drive the wearer right straight up the fucking wall for hours, with no relief in sight.

I am such a stinker.

Fortunately, the world is saved by the mere fact that I don't at the moment have time to actually build one of these. Yet.


( 75 comments — Leave a comment )
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Jul. 21st, 2007 08:16 am (UTC)
I was thinking of the mechanical aspects of vibrators ever since I first saw my first pearl rabbit back in the 1990s as a recently graduated mechanical engineer - with the power of chips today, those wave forms seem like the way to go with improving the performance of devices over the 20 minute one shot vibrators that Trojan is now selling in drug stores across the country.
Jul. 21st, 2007 07:58 pm (UTC)
From a strictly implementation standpoint, the hard part is the interface. Building a computer interface to a vibrator is more tricky than it sounds. I tried to do that a couple years back, and nearly started a fire; one of the resistors in the analog part of the circuit actually exploded. Then I sat down and did the math and realized that a typical 3-volt vibrator can draw as much as six watts(!) of power, and putting six watts through a carbon-film resistor rated at 250 mW doesn't work so good.
(no subject) - sevoo - Jul. 22nd, 2007 03:38 am (UTC) - Expand
(no subject) - kahoki - Jul. 22nd, 2007 11:49 am (UTC) - Expand
(no subject) - pstscrpt - Jul. 22nd, 2007 06:44 pm (UTC) - Expand
(no subject) - tacit - Jul. 24th, 2007 06:29 pm (UTC) - Expand
Jul. 21st, 2007 10:34 am (UTC)
actually you may need the help of an electronics person for this, I volunteer
Jul. 21st, 2007 07:59 pm (UTC)
You good with relatively high-power digital-to-analog stuff?
(no subject) - (Anonymous) - Jul. 22nd, 2007 01:37 am (UTC) - Expand
(no subject) - tacit - Jul. 24th, 2007 06:31 pm (UTC) - Expand
(no subject) - qdot - Jul. 26th, 2007 04:32 am (UTC) - Expand
Jul. 21st, 2007 01:01 pm (UTC)
The reason why the sum of sine waves (in either the FFT version or the fibonacci series) is periodic is that the sine waves being summed all have commensurate periods. The FFT is a fast way of summing sine waves of frequencies f, 2f, 3f, 4f, etc. (It definitely overkill for this application, btw). The fibonacci sequence sums sine waves of frequencies f, 2f, 3f, 5f, 8f, etc. In both cases, the resulting waveform will repeat with period 1/f.

However, if you sum sine waves with non-commensurate periods, the resulting waveform has an infinite period and never repeats. I'd suggest frequencies of f, φf, φ2f, etc. where φ is the golden mean, approximately 1.618.
Jul. 21st, 2007 01:59 pm (UTC)
ack! I'm surrounded! I even chose to *live* with you...
oh the horror!
(no subject) - 6_bleen_7 - Jul. 21st, 2007 07:16 pm (UTC) - Expand
(no subject) - tacit - Jul. 21st, 2007 07:53 pm (UTC) - Expand
(no subject) - 6_bleen_7 - Jul. 22nd, 2007 02:28 am (UTC) - Expand
(no subject) - tacit - Jul. 21st, 2007 07:52 pm (UTC) - Expand
(no subject) - 6_bleen_7 - Jul. 22nd, 2007 02:29 am (UTC) - Expand
(no subject) - blaisepascal - Jul. 22nd, 2007 04:03 am (UTC) - Expand
(no subject) - tacit - Jul. 24th, 2007 06:34 pm (UTC) - Expand
Jul. 21st, 2007 01:58 pm (UTC)
*runs from the scary mean vibrator*
Jul. 21st, 2007 07:53 pm (UTC)
I am a bad, baaaaad man....
(Deleted comment)
Jul. 21st, 2007 08:39 pm (UTC)
I'm usually around online in the mid afternoon on weekdays. Not often online weekends or evenings.
Jul. 21st, 2007 03:11 pm (UTC)
this whole subject is flawed i think... this is completely ignoring the idea that a woman could possibly have control over her own orgasms. Even if you use this type of programming as a distraction for the woman instead of a tool for her to achieve orgasm, you're ignoring psychological influences and stimulus. If you're aiming for her to be driven up the wall, you need to make sure she's not meditating and provide verbal stimulus as well i think.

i'd love to test your prototype, though. :)
Jul. 21st, 2007 07:55 pm (UTC)
Okay, you make a good point. I've known a woman who can give herself an orgasm simply by squeezing her thighs together, and another woman who can come from verbal stimulation alone, so my Evil Device won't have the intended effect on everyone.

Still, I think that women with that kind of control over their orgasms are scarcer than women who don't have that kind of control, and of course, there's always tickling or other distractions that might be helpful as well...
Obvious response - wompa - Jul. 26th, 2007 09:57 pm (UTC) - Expand
Re: Obvious response - tacit - Jul. 30th, 2007 09:29 pm (UTC) - Expand
Jul. 21st, 2007 03:13 pm (UTC)
You know, before now, I just thought you were interesting. Now I think I have a crush on you...
Jul. 21st, 2007 07:56 pm (UTC)
Is it that I think about sex all the time, or because I use my powers for Evil?
(no subject) - quaryn_dk - Jul. 21st, 2007 09:14 pm (UTC) - Expand
(no subject) - kerrileigh - Jul. 22nd, 2007 03:24 pm (UTC) - Expand
Jul. 21st, 2007 04:46 pm (UTC)
find the time!! please, for the love of GOD find the time!!!
Jul. 21st, 2007 08:00 pm (UTC)
Y'know, I wouldn't think there'd be all that many people interested in a toy that's intended to drive the victim user absolutely insane...
(no subject) - gentleindiff - Jul. 21st, 2007 08:07 pm (UTC) - Expand
(no subject) - lunasmiles - Jul. 24th, 2007 08:25 am (UTC) - Expand
(no subject) - tacit - Jul. 24th, 2007 07:07 pm (UTC) - Expand
(no subject) - 31504 - Jul. 22nd, 2007 09:53 pm (UTC) - Expand
(no subject) - tacit - Jul. 24th, 2007 06:37 pm (UTC) - Expand
(no subject) - dwer - Jul. 23rd, 2007 04:57 pm (UTC) - Expand
(no subject) - tacit - Jul. 24th, 2007 07:04 pm (UTC) - Expand
Jul. 21st, 2007 04:50 pm (UTC)
When you're ready for beta testers.. ;)

Actually, as you know, I have the Je Joue, which is supposed to bring in that random element that is controllable via programming. As someone who rarely finds success with vibrating toys.. not even the Je Joue is overly pleasing to me (other than the geek points.)

I think I have to agree with beckycaret above.. for some women, there might need to be another element involved than technology alone.

But I know you're up for that task ;)
Jul. 21st, 2007 08:01 pm (UTC)
Seems like it might be fairly easy to program a Je Joue for pseudorandom vibration, though of course that kinda defeats its intended purpose.(And they're a bit spendy.) I appreciate the vote of confidence in my "other element" skills, though! :)
Jul. 21st, 2007 11:03 pm (UTC)
The world isn't very saved, as there are those of us that have built this many times over, and really all you're needing is the interface (which I'm currently working on, my software will actually do function generation and interpolation. ^_^)

http://www.slashdong.org is my website, check it out if you're interested. ^_^ (And this is so getting blogged about)

And, if you just want to get the hardware controller board now:


Er, d'oh. Hell, looks like he sold out of the prebuilt boards.
Jul. 21st, 2007 11:05 pm (UTC)

Wait a second.

You're the Onyx/SymToys guy. You know all this already and were doing it before I was. My mistake. ^_^
Jul. 21st, 2007 11:07 pm (UTC)
Aaaaaaaaaaaaand one more thing: To truly make this evil, mix in some biometrics. ^_^
Jul. 24th, 2007 06:38 pm (UTC)
Ooooh. Biometrics. Feedback from vaginal contractions maybe...

Now THAT is evil. Truly. My hat's off to you!
(no subject) - cheetah_spotty - Jul. 25th, 2007 04:50 pm (UTC) - Expand
(no subject) - qdot - Jul. 26th, 2007 04:35 am (UTC) - Expand
(no subject) - tacit - Jul. 30th, 2007 04:31 pm (UTC) - Expand
(no subject) - (Anonymous) - May. 24th, 2009 07:35 pm (UTC) - Expand
Jul. 22nd, 2007 03:35 am (UTC)
Which one of Mom's vibes will work the best?
ok, this is like a kid's science project on sex toys... judging on the scientific graphs provided of course ;)

btw, check out my latest post. I met a sex magick high priestess from Atlanta... you may not be into sacred sexuality but she was from your neck of the woods and i thought that was interesting.

Jul. 24th, 2007 06:45 pm (UTC)
Re: Which one of Mom's vibes will work the best?
Neat! What's scary is I actually know more kinky poly folks in Chicago than in Atlanta these days.
Jul. 22nd, 2007 09:11 pm (UTC)
Let me know when you have these ready for purchase, kthxbai!
Jul. 23rd, 2007 02:52 pm (UTC)
Fortunately, the world is saved by the mere fact that I don't at the moment have time to actually build one of these. Yet.

But when you do, I definitely have someone who can beta-test for you.

Jul. 24th, 2007 05:18 am (UTC)
In another dimension I would be a high school math teacher, and this sounds like the perfect sort of "real world" problem that would get high schoolers really interested in math :)
Jul. 24th, 2007 07:05 pm (UTC)
Heh. Now THAT would be interesting. I bet it'd generate some newspaper articles and more than a few irate parents...
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( 75 comments — Leave a comment )