How Do 'Singing Magnets' Work?

dpbsmith asks: "Singing magnets are available at all of the usual geek-toy emporia, and, for all I know, ordinary toy emporia as well. They consist of a pair of magnets made of a polished substance with the general appearance of hematite. What is surprising, pleasing, and unexpected is that when the magnets strike each other under their own power, they produce a sharp, loud buzz that rises in pitch. The sound lasts a good fraction of a second and climbs somewhere into what sounds like the 200-500 Hz range. The exact sound and its duration are somewhat unpredictable and depend on how the magnets happen to strike each other. It is a little like the sound that you get when you mash a pingpong ball against a pingpong table with a paddle. What physics are involved in the production of these sounds?" "Google searches turn up some forum postings that indicate that it is a synthetic magnetic substance similar to hematite that's available cheaply in China as an industrial byproduct. The singing magnets are a little larger than size of olives; the shape is similar to a (U. S.) football but slightly more elongated. Their major axis is about 5 cm long, their minor about 1 cm. They are fairly powerful and will jump together when placed on a desk about three inches apart. They can distort the colors on a CRT display from a distance of over 20 cm.

Contrary to expectation, the poles of the magnets are oriented along one of the minor axes of the ellipsoid, not the major axis.

Neodymium magnets in 'ordinary' shapes produce boring 'plinks' when they snap together. Something about the shape of these magnets makes the sound much longer-lasting and entertaining. It is not simply the bounding rebound of two objects made of stiff-but-elastic material. Transfers of linear to angular momentum are clearly involved.

If course, I'd love to know whether these things were 'invented' or 'discovered', and by whom, trying to do what.

Comments

Um.

[Solder Fumes]

Despite what you say, they are just bouncing off each other. The modulus of elasticity is high, and because of the shape of the objects they can only contact at one point. The magnet pulls them together and they bounce apart, the point of contact possibly traveling along the curve of the objects depending on how much energy remains. They might maintain a semi-constant tone because this contact point travels to where the mass of the objects is less, at the ends, allowing them the bounce apart at the same frequency despite energy being absorbed in the material.

I don't have any so I can't verify this theory.

Bouncing

[avalys]

It's definitely just them bouncing apart and colliding until they give off all their potential energy as sound.

If you listen, you can hear the pitch of the sound getting higher and higher as they start to hit each more frequently, until they stop moving.

Re:wow

[JRIsidore]

I guess you mean the right thing, but your description is not quite right. With a regular pendulum the force is not constant but a linear function (in a first approximation) of the amplitude. The further you move the pendulum from the point of rest the stronger is the force which pulls it back. This linear dependence causes it to swing with a single constant frequency.
Now for the singing magnets the force must show some non-linear dependance on the amplitude, which allows (or better: forces) it to oscillate at several frequencies. Might be interesting to actually calculate it...

Re:Amazing explanation

[eluusive]

From their website:

With The Wine Clip, a wine's impurities and tannins are broken down during the pouring process. There is absolutely no chemical change and nothing is introduced or taken away from the wine.

The taste of many small molecules is smoother than the taste of fewer large molecules.

Hmm? No chemical change? But it still breaks up molecules? WHOA.

slight correction:

[Anonymous Coward]

"...simply plugging appliances into mains outlets in decending order of power consumption"

Sorry, that should have been "plugging appliances into power boards". Using different mains outlets around a room can cause the same ground problems. And always calculate the total loading.

Oh, and while I'm ranting: "Oxygen Free Cable"? If it's shiny, its oxygen free, you golden-eared idiots. Besides, most cable deteriorates because of chloride contamination from the PVC sheath, not because of oxygen (which is why we have "blackwire" syndrome; copper oxide is green, not black). And despite years of research, there is still not a shred of evidence that "microdiodes" really exist inside bulk copper.

Re:Indeed

[rco3]

I'm sorry; did you just say that "$1,200.00 is not that much for a high quality digital cable"?

Did you mean that to imply that there is some set of conditions, liable to be encountered in a home audiophile environment, under which there is ANY justification at all for a $1200 digital interconnect? That there is any way in which that cable will actually outperform a $2.99 Radio Shack coax cable?

Because, being the great exposer of snake oil that you are, I'm sure you're aware that the only way a DIGITAL interconnect will negatively affect the signal transmission is if it is seriously fucked-up BROKEN. No competently-designed piece of audio gear will have any trouble accurately and errorlessly decoding a digital signal passed over, say, a straightened-out wire coathanger, much less a decent piece of coax. The most you will need to spend on a piece of coaxial digital interconnect, for audio usage, is about $5. Anything more than that is marketing. Gold-plated connectors, oxygen-free copper, pure silver litz wire - none of that is necessary.

You must have meant that that particular purveyor of patent nostrums isn't asking more than other such fleecers of the unwary ask for such things. You couldn't possibly have meant that $1200 for a digital interconnect was justified.

Right?

Re:Singing Sword

[s0l0m0n]

You are unaware of the basics of metallurgy in steel, as well as of 'singing' in swords.

A properly made sword rings when tapped. This is because the fittings (hilt, pommel and handle) are tight, and do not dampen vibration. If the blade has any cracks, these will also dull the ring of a sword.

Additionally, a good western sword flexs a fair amount during cutting or thrusting. This in itself is not a positive or negative feature. However, a blade that returns too much vibration to the hand may be uncomfortable to use (think about how a bat stings your hands when you hit something with it).

The addition of chromium to a steel in quantities of over 13% makes 'stainless' steel. Not only does the addition of high levels of Cr make the steel resistant to stains, it makes in more 'deep hardening'. This is in refference to the cooling of steel from the the point at which all of the carbon in the steel is disolved in the solution(AC1, also called the Currie point, which is generally above 1350 degress F) down to below the point(MS, below 900 degrees F) at which martensite (hardened steel) is formed.

In this process, a variety of different crystaline forms can be produced. If you cool slowly, you will probably end up with pearlite. This is soft, and relitively flexible, and not at all good for blades. If you cool faster, you will end up with grains (crystals) of martensite, which is harder, and more springy (once tempered) much better for knives and swords.

Now, back to why stainless is bad for swords. Stainless is deep hardening because the chromium pins the edges of the grains (crystalline stuructures of carbon and iron), preventing them from growing when heat is applied. Smaller grain sizes lead to increased hardness. Unfortunately, the introduction of the chromium into the edges of the crystals causes them to be less strong. This leads to lower flexiblity. Lower flexility leads to swords that fail castastrophically durning use.

I'm not a metallurgist by any means, but I have made a half dozen swords, a hundred plus knives, and been studying heat treating of swords for about a dozen years. Please, spend 300+$ on good old fashioned carbon steel if you must have a sword. Heck, even get a good stainless steel sword from Rob Criswell or one of the Dawsons, but quite buying that cheap stainless crap on ebay and in the Mall cutlery stores. Support a sword smith with real talent, here in the US. There are lots of us, It's a better deal in the long run.

Josh Powell, owner and operator of Josh Powell Custom Knives.

Sounds like ass

[Pan T. Hose]

I am sure that none of us would want to hear any jitter that sounds like ass--i.e. like this--but that doesn't mean that any of us would buy a $1900.00 USB cable. Also, the USB power is strong enough to power the iGrill (which is great, by the way, because now I don't have to carry around the bulky Zero-Point generator while I'm hunting when I have a laptop anyway), so we also don't have to worry about the power line impedance so much, unless we use kilometres long USB cables, which is not so popular as it used to be with null modems any more, since we have an easy access to the Interweb.

Now seriously, I have noticed that people usually stop listening when I start talking about the "science stuff" so they don't really care if it is Fourier series or quantum cleaning of dirty electrons, since they don't listen anyway. As long as it sounds scientific, it is scientific, for all they care. And of course I must be lying to them because I am only their friend while the guy who just sold them a wooden potentiometer knob for $500 must be an expert, because otherwise he wouldn't have a job selling expensive equipment, right? Here the cognitive dissonance kicks in: "I am not a sucker, but I have just bought an ugly wooden knob for $500, therefore people who say that buying ugly wooden knobs for $500 is dumb must be mistaken."

Now, when they say that it was an "expert" in the audiophile store who has told them--or the "expert" in the Stereophile Magazine who has written--what they are telling you about, what they need here is a good ipse dixit and argumentum ad populum, for they won't listen to any other argument at all.

At that point, I usually shout at them: "Does Deutsche Grammophon use this junk to 'purify' their music while they record it? No? Then why on Earth do you think I need it to listen?! Now, will you excuse me, I need to drink my snake oil," and I leave in furious anger. Later when I talk to them, they sometimes ask me: "Are you serious that the record industry don't use such cables? Why?" To which I answer: "Because they are not bloody idiots, that's why! Do you need to spend millions on sound equipment? Then go to the recording studio, see what they use, and buy the same stuff. You will still be a sucker to buy something that you don't need, but at least you will have something that actually works."

It is surprisingly difficult to explain the truth to anyone who have bought audiophile lacquer or the wine clip, but it is still nothing compared to e.g. homeopathy or any other quackery when we are talking about peoples' health and lives, not just some useless junk. People will just not accept that they are suckers. Remember this story?