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How Do 'Singing Magnets' Work? 89

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.
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How Do 'Singing Magnets' Work?

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  • Bounce. (Score:2, Insightful)

    by Anonymous Coward
    They bounce apart, attract togethor, bounce apart again, etc losing energy each cycle until they can bounce no more.

    Okay, that was a wild ass guess.
    • Re:Bounce. (Score:3, Interesting)

      It's also true. I had these when I was a kid, and by pushing them towards eachother, I could make the sound louder, and by muffling them with my hands, I could damp them out. That has to be vibratory acoustics. Plus the sound TOTALLY trips out my son, makes him giggle like you wouldn't believe.
  • Not physics (Score:5, Funny)

    by Anonymous Coward on Friday January 21, 2005 @06:26PM (#11436758)
    This is clearly the work of witchcraft! BURN HIM!!!
  • Um. (Score:5, Informative)

    by Solder Fumes ( 797270 ) on Friday January 21, 2005 @06:34PM (#11436843)
    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.
    • Re:Um. (Score:4, Insightful)

      by itwerx ( 165526 ) <> on Friday January 21, 2005 @10:36PM (#11438476) Homepage
      Despite what you say, they are just bouncing off each other.

      Additionally, the central location of the poles helps to maintain equilibrium and reduce the range of possible contact points.
      (Unlike a round magnet which would have a wider range of effective contact points thus allowing more slop in the bounce cycles with a coincident reduction in tonal quality).
    • Re:Yup. (Score:5, Interesting)

      by Bastian ( 66383 ) on Friday January 21, 2005 @11:03PM (#11438598)
      I have a pair, and this is the only explanation that makes sense to me. I imagine that the effect would also happen on a whole range of rounded magnets of this type, but with the length of the "buzz" varying - the stretched football shape is probably just one of the more effective ones.

      If you try to isolate the system by throwing them up in the air so they pull together and strike each other while airborne, they will generally buzz for quite a long time - generally, it stops because the motion was dampened by your hand (or whatever else they land on) rather than coming to a stop on its own.

      The whole effect is made even more fun because if you throw them in the air, they will spin around each other like a cat in zero gravity. []
    • Probably very similar to those springy doorstops when force is applied laterally.

      Example []

      The cats LOVE those things.

    • "The modulus of elasticity is high, and because of the shape of the objects they can only contact at one point."

      Also, their shape probably reduces the contact with the supporting surface, which prevents the ringing from being damped out.

  • Obviously this is a redisovery of the process used to create Flamberge, the Swinging Sword.

    Very useful if Prince Valiant needs a replacement sword.
    • by dougmc ( 70836 )
      Flamberge, the Swinging Sword.
      Is that the Flamberge that puts the `Grrrr!' in `Swinger', baby, yeah?
    • Re:Singing Sword (Score:1, Interesting)

      by Anonymous Coward
      For those unaware of what a "singing sword" actually is (and they are real, though not magical) it refers to a sword forged in such a way that the crystalline structure of the metal is highly organized. This wasn't easy to accomplish with low-temperature forges and beaten steel, so such swords were highly prized.

      Today we call this metal "stainless steel", and blades made from it are found in just about every kitchen.
      • Re:Singing Sword (Score:5, Informative)

        by s0l0m0n ( 224000 ) on Sunday January 23, 2005 @04:03AM (#11446585) Homepage
        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.
      • Only a fool would go after the Singing Sword...
  • by ZSpade ( 812879 ) on Friday January 21, 2005 @06:45PM (#11436951) Homepage
    No make that scream...

    I took the magnets out of an old SCZI drive bigger than my head, and pried them apart with a screwdriver.

    Well I was holding a magnet in each hand, and while I was walking they got a little too close, and my was caught in-between. Oh I sang, like a little girl in church choir.

    Long story short, I didn't need stitches, but I did have one very bruised bone, not to mention my ego...
  • Bouncing (Score:3, Informative)

    by avalys ( 221114 ) * on Friday January 21, 2005 @06:47PM (#11436965)
    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.
  • wow (Score:5, Insightful)

    by Optical Voodoo Man ( 611836 ) on Friday January 21, 2005 @07:09PM (#11437166)
    This is blowing my mind. You would think it should be a constant frequency with decay, like the classical pendulum. The difference between the classical pendulum and this case is that for a pendulum, the force is constant; with the magnet, the force is inversely proportional to the distance between the magnets. As the energy in the velocity (E=1/2mv^2) is converted to heat, the magnets have a lower velocity so they travel a shorter distance away from the other magnet. The closer the magnets are, the greater the force, again reducing the period between "clacks". The frequency increases because the magnets have a non constant in the force between them (the force increases as the reciprocal of the square of the distance).
    • Re:wow (Score:2, Informative)

      by JRIsidore ( 524392 )
      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 oscillat
    • I believe you are right. However, the assumption you make that you use the velocity equation is only partially true. Magnets utilize the electrostatic force... and that force is (kq1q2)/r^2 ..... the inversely proportional to the square of the distance. we talked about this in physics yesterday - only reason I knew :P
      • Magnets utilize the electrostatic force... and that force is (kq1q2)/r^2 ..... the inversely proportional to the square of the distance. we talked about this in physics yesterday - only reason I knew :P

        You apparently didn't listen close enough.

        Magnets utilize the magnetostatic force, not the electrostatic force, which is attraction between charges, not magnets.

        Magnetic attraction is far more complicated, because there aren't any "magnetic charges", just constrained loops of magnetism. It really depends
  • by torpor ( 458 )
    .. it is the 'sound of the magnetism itself', which is to say, the 'out of balance' nature of the two magnetic forces reflective attraction for each other, pitched over time, much as a delay line, while things stabilize and the energy of the initial collision dissipates ..
  • by Pan T. Hose ( 707794 ) on Friday January 21, 2005 @07:45PM (#11437463) Homepage Journal
    I'm sure that the guys who are selling audiophile lacquer for $200/oZ [] and wooden potentiometer knobs for $500 a piece [] will have a much more amazing explanation involving quantum audiodynamic subparticle field wavetransformation theory, that not only makes your audio equipment sound more open and free flowing with a nice improvement in resolution, better dynamics and improved overall naturalness, but also improves the taste of wine [] making it older in a matter of seconds (a widely known property of magnets), but I--a boring scientist--will only tell you this: they bounce.
    • Mod this guy up, stop the voting, give this guy the ten thousand dollars. That was sweet.
    • by deglr6328 ( 150198 ) on Friday January 21, 2005 @09:30PM (#11438118)
      Holy. Fucking. Shit. [] Audiophiles are the stupidest people on earth.
      • Indeed (Score:3, Funny)

        by Pan T. Hose ( 707794 )

        Holy. Fucking. Shit. [] Audiophiles are the stupidest people on earth.

        $1,200.00 is not that much for a high quality digital cable, but notice the arrows on the pictures. They indicate the direction in which the sound should flow. Of course it works best with quantum sound purifiers [] which strips electronic noise from individual electrons. When you are at it, don't forget to buy your tuning dots []: "Marigo's VTS Tuning Dots have been one of the most effective and dramatic steps I have taken to improve my s

        • Amazing. (Randi is simply amazing, that man seems eternally (supernaturally?? :-)) tireless in his relentless attacks on charlatanism) I don't think I will ever cease to be amazed at the truthfulness of the maxim- fools and thier money are soon parted.
          • Hmm, someone should tell him to tackle the paranormal beliefs of the current US president ("we're winning the war in Iraq!", "no I didn't go AWOL during Vietnam!"), no one else seems to have been able to get the public to listen to their fact-proven arguments against bush.
        • Re:Indeed (Score:3, Informative)

          by rco3 ( 198978 )
          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 in
      • by Bastian ( 66383 )
        I'm still more amazed by the high-end USB and FireWire cables that companies like Monster are selling.
        What part of DIGITAL don't people understand?
        • by Anonymous Coward
          "What part of DIGITAL don't people understand?"

          In my experience (and I bought one of the earliest iMacs with USB & FireWire, so I've had more than most) the gague of cable does have a significant effect on the operation of some bus-powered peripherals. If the cable run is too long (or the gague too small), series resistance can cause voltage drops that may prevent the device working properly. Bus powered hard drives exhibit the most obvious symptoms (refuse to spin up), but there have been occasions wh
          • slight correction: (Score:2, Informative)

            by 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
            • which is why we have "blackwire" syndrome

              Ooooh. Often wondered about that. It seems to be worse on wire that gets damp - repairing electrical connections in cars is often difficult. Funny it always seems to be the negative leads - and the negative lead of NiCads are by far the worst I've seen for it!

    • 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.
    • by Anonymous Coward

      Fascinating stuff. An utter load of crap sold at a substantial profit, all through the magic of ubfuscatory language.

    • Hah. Great links. You hit the nail on the head with "(a widely known property of magnets)." That's got to be near the top of my bad science pet peeves list. I saw a safety razor shaving kit at Sharper Image once with a storage base that used a magnet to "keep the blade sharp." I can't find it on their website now, perhaps their guilty consience got the better of them...or more likely they just had to make room for a cd-playing, golf swing improving, massage chair...with magnetic therapy cushions. It w
      • It was basically this idea [] but in a fancier, higher-tech looking package, and more expensive.

        "Sharpen razors overnight with a patented proprietary magnetic field. After each shave simply place the blade edge on the Razor-Mate. Razor blades are reported to last up to ten times longer, and give a smoother, closer shave." Looks impressive, but I only use free magnetic fields and I am strongly against field patents.

      • by Anonymous Coward
        You know, back in my day, they didn't have magnets for keeping razors sharp - the fad back then was using a small pyramid (I kid thee not). This pyramid would not only sharpen razor blades, it also gave water stored in it miraculous healing properties...

        As PT Barnum may have said, "there's a sucker born every minute".
        • You know, back in my day, they didn't have magnets for keeping razors sharp - the fad back then was using a small pyramid (I kid thee not). This pyramid would not only sharpen razor blades, it also gave water stored in it miraculous healing properties...

          That's nothing! Back in my day, when we wanted miraculous healing properties of water, we used radium ore []: "By the patented composition of highly selected and scientifically compounded radium ores of which the Revigator is made, this lost element is

  • Ok, I'll probably lose mod points for this, but I can't be the only one to read that as "How Do Singing Midgets Work?" And here I was so excited to find out if singing midgets really do have to work harder to stay in show-business.
  • but I'd imagine that's the sound of the two magnets being propelled into each other at glancing angles by the force of their magnetic fields. Over time, the magnets get closer and closer together at the peak of each bounce as the magnetic fields dampen the oscillations (um ... the bouncing, I mean). Sort of like a spring system. As the magnets get closer together, they hit more frequently (since the force of magnetic attraction increases as they get closer -- if they were joined by a spring, it would get we
  • I have an idea... (Score:3, Interesting)

    by syukton ( 256348 ) * on Saturday January 22, 2005 @12:39AM (#11439013)
    Go here:

    View their "Ball Bouncer Demonstration"

    I have a hunch that these "singing magnets" are coated with a Liquidmetal-like material which preserves some 99% of the impact force and returns it quite energetically, causing the magnets to come together, be pushed apart, come together, be pushed apart, fast enough to create a "tone" of sorts.

    When the ball gets to the end of the ball bouncer demonstration, it does largely what the original poster was asking about with regard to the sound it produces.
  • I just thought it was funny that the linked product page, under features, says "Toss them into the air and they'll 'sing!'"
  • my collection of singing potatoes, who help me maintain my grip on reality, tells me there's no such thing as singing magnets.
  • See how the bounce frequency goes up as the ball bearing loses energy?

"Don't discount flying pigs before you have good air defense." -- jvh@clinet.FI