FAIL.
Here's a seriously divergent thread topic, pasted from an old Lounge thread on magnetic recording and coercivity....written by yours truly:
There's no WAY any sort of speaker magnet can erase the data on a hard drive. That was an old floppy disc trick, but is completely ineffective on the HDD.
The
coercivity (measured in Oersted = Öe) of the media inside an HDD is insanely high compared to a floppy disc. (One of our newer HDD designs is in the 5250Öe range vs. roughly 800Öe for a floppy disc. You'll never generate enough magnetic field with a speaker to change the magnetic domains on the surface of the disk.
Keep in mind, the actuator assembly (where all the read/write heads are mounted) itself is basically a magnetic "sandwich" that sits right next to the outer tracks of the disk. If simple magnetism was enough to erase data, you'd never have any data in the first few thousand tracks of your drive!!
There ARE products that can actually erase a hard drive..... here's one for example:
http://www.fujitsu.com/us/services/c...asure-p3m.html
A bit more involved than the "speaker trick" but this thing generates enough magnetic field to completely destroy all the user data, as well as all the original servo position information, factory format, and even blows the read elements on all the heads! Very satisfying indeed....
It is interesting to note that with the increasing areal densities that HDD manufacturers are pursuing, the coercivities are being pushed much higher. So high in fact, that the magnetic domains won't even change state when a magnetic field is applied by the write element...the magnetics are simply too strongly biased in their current positions. The drive actually has to use a small heating element located just above the media to heat the appropriate sector just before it attempts to write data. This temporarily reduces the
coercivity and allows the data to be written.
Seagate calls this technology HAMR (Heat-Assisted Magnetic Recording)...
Cool stuff.
