Can a (notebook) hard drive be affected by magnets, such as those in a headphone or a cell phone'?

Question

I would like to carry the notebook computer around, together with the ear-bud headphones and the cell phone. But since ear-bud headphones have magnets into it, can't it affect the notebook's hard drive?

I think cellphone is more common for people to carry around with their notebook, except cellphone is usually in the pants' pocket or on the belt on the waist...

Solution 1

Hard drives themselves have some of the more powerful magnets available to control the read-write head and are completely impervious to anything you could set on them.

See this article from PCWorld busting PC myths: http://www.pcworld.com/article/116572/busting_the_biggest_pc_myths.html

The only magnets powerful enough to scrub data from a drive platter are laboratory degaussers or those used by government agencies to wipe bits off media. "In the real world, people are not losing data from magnets," says Bill Rudock, a tech-support engineer with hard-drive maker Seagate. "In every disk," notes Rudock, "there's one heck of a magnet that swings the head."

And as far as flash drives/cards go:

A magnet powerful enough to disturb the electrons in flash would be powerful enough to suck the iron out of your blood cells

You can see the magnets in a hard drive as a large silver piece screwed down on the other side of the read-write head on this page: http://computer.howstuffworks.com/hard-disk6.htm

Solution 2

There are speaker boxes inside most notebook machines which are far more powerful than those within earbuds or cell phones. Many people put additional speakers around their machine to have better (or at least louder) sound output.

The rumours that you could destroy floppies when you accidentally put them onto your speaker boxes seem to linger still. ;-) Don't worry, though. Unless you expose your machine to serious magnetism (anything that would visibly distort a CRT display from across the room or worse) you'll be fine. The notebook's chassis and the drive's case will shield off quite a lot, and the platter materials are far better today than they were in the past.

Just don't worry, for any possible everyday use you'll be safe.

Solution 3

The magnets in the headphones wouldn't be strong enough to crash a Hard drive, whereas a magnet from full blown loud speakers may. You'll be fine carrying them with your notebook.

Most HDD crashes are due to them being knocked around or something.

Comments

[HikeMike]

I once placed my iPhone on a laptop and it immediately crashed hard. No idea if that was just coincidence or due to something like this.

[Prerak Diwan]

If the hard drive is so sensitive to magnets like that, then you have a bad hard drive.

[Olfan]

Of course you're right. But if your bad hard drive is losing all your data, then you have bad luck which is slightly worse. ;-) I'd recommend against exposing your drive to large-scale dancefloor speakers in full action, but that's not everyday use anyway unless you're a DJ.

[Prerak Diwan]

.. it was a joke :)

[Olfan]

Not a myth if you look in the right time and place. Damage not only depends on the strenght of a magnetic field but also its direction and focus. To destroy data it's sufficient to flip only a few bits, it's not necessary to completely erase the whole drive. There has been an issue in German railway cars back in 1998 where the folding tables could (and did!) erase hard drives. I can only offer a link in German Language, but here you go: heise.de/ct/artikel/Loeschzug-286254.html. Heise is a well-renowned publishing house and the article is not of April 1st so I'm ready to trust it.

[d-_-b]

@Olfan, Your computer most likely has a hard disk, which has very strong magnets. Most magnets, even those in small speakers, will visibly distort a CRT.

[Olfan]

Hard disk magnets are rather powerful, but their magnetic field is so very focused it will not touch the spinning platters which contain the data. As for the CRT, I edited my answer to better reflect what I actually meant. I'm referring to magnetism that bends and warbles the picture from across the room, not while touching the tube.

[Olfan]

Google images for "permanent magnet with a focusing pole piece" and you will see a lot of hard disk magnets. Along with many of the images comes a lot of information on how to make them.

[John Dvorak]

@Olfan if you mean Halbach arrays - no, that won't work. The head actuator is a linear motor, and it needs a linear magnetic field. To use a Halbach array for actuation, you'd need a pair of carefully positioned electromagnets powered by altertating currents. This would most likely hamper the speed with which the head controller can position the head. The linear motor only needs two pulses of direct current (= 4 pulses of voltage) - one to get the head moving, one to stop it. I have actually measured those peaks as a lab assignment.

[Olfan]

As a layman, I've used a far less elaborate test: Screw open an old hard disk, get the magnets, try to move things with them. The front end does move things, the sides do not. ;) I'm sorry if that reads trivial, but it's enough to not damage the data in the factory build setup but that same data being susceptible to the very same magnets if they are moved directly over the platter.