What is the noise computers make when they are working?
October 5, 2010 4:24 AM   Subscribe

Why do computers often make a sort of grating noise when they are working?

I often hear computers making a noise that is hard to describe. It sounds sort of like running your fingernails quickly over a plastic grate. It's most common when you have just started a program and it is loading up. What causes this?
posted by giggleknickers to Computers & Internet (8 answers total) 4 users marked this as a favorite
That's usually the sound of the hard drive's read heads rapidly moving back and forth to access bits of data from all over the hard drive platter. Defragment and the sound will diminish a bit, but not completely.
posted by AzraelBrown at 4:29 AM on October 5, 2010 [2 favorites]

AzraelBrown has it. See HowStuffWorks. Here's a YouTube clip of a working drive making that sound.
posted by purephase at 4:48 AM on October 5, 2010 [2 favorites]

Depending on how loud that sound it is, a noisy hard drive can be a sign of a failing hard drive. Some clicking/ticking and grinding is normal, but if the noises are growing louder or more frequent or changing, you may have trouble brewing.

Are you backed up? Doesn't matter if it's a brand new drive or if it's perfectly healthy. Get backed up. Data on a hard drive doesn't exist if it doesn't exist in at least one other place.
posted by fourcheesemac at 5:16 AM on October 5, 2010 [1 favorite]

Do you have a computer that still has a floppy drive? When an app thinks it has to check the floppy drive (maybe because there's something in the recent files list that was on a floppy), you may get the grating sound of the drive trying to read without there being a disc in the drive. (Or am I the only one who still has a computer with a floppy drive in it?)
posted by aught at 5:53 AM on October 5, 2010

Computers store information on hard drives, in what are called "sectors" on the rapidly-spinning magnetic disk. A little radial arm on the drive moves back and forth on it to read various sectors, much like the needle on a record player would, except it moves left and right to find the information it needs very rapidly.

When you first start using a near-empty drive, things start to fill up in a reasonably civilized order - modern computers are smart enough to put stuff together in an order similar to what you'd find on a vinyl record, so that the "needle" (the read head, really) can read as much of a file as possible with as little movement as possible.

As the drive gets filled up and the space starts go get emptied and reused (let's say you delete a few dozen completely legal MP3s at 4MB each, and then download a perfectly legitimate podcast at 40MB) the computer will fill those 4MB slots with part of that 40MB file, and note to itself that 4MB of it is here, and 4MB is over there, and 8MB is in that other spot, and so on.

And then the drive head will shift left and right quite quickly, to read that file when you ask for it, as well as doing all the other stuff your computer does quietly in the background for you.

That's what you're hearing, is that rapid shifting left and right. You should know, though, that older hard drives that start to make that particular noise (especially if you hear a louder "klunk" noise periodically in there) are frequently loud because they're on the verge of failing. As mentioned above, make sure you've got whatever's important to you saved somewhere else if your hard drive starts getting too loud, either burned to DVD or saved on another hard drive - USB keys aren't a reliable mid- or long-term storage medium.
posted by mhoye at 6:38 AM on October 5, 2010 [2 favorites]

If it's not the hard drive making the sounds then the other alternative is that part of a drive cable is lightly touching a fan.

The reason the sound is heard more when you start programs is because the CPU starts to work more which generates more heat and the fan has to speed up to keep the temperature consistent.
posted by mr_silver at 8:10 AM on October 5, 2010

Are you backed up?

This is the most important thing anyone's said here. Some hard drive noise is normal; some is the sign of impending doom. If you're asking this question, it sounds like you may not know the difference.

Don't chance it. Mozy, Carbonite, and Dropbox all have free/cheap cloud backup services that are easy to install and use, and you can buy a terabyte of external USB hard drive for around a hundred bucks right now. (I recommend using one with Cobian backup, a great, easy to use and free program).

Hard drives always fail when you least expect it! No excuse to get caught unprepared.
posted by Erroneous at 11:06 AM on October 5, 2010

Again, heed fourcheesemac.

Are you backed up?

It's happened to me. I started hearing the sound, but kept using the computer because it seemed to be working just fine. A few days later, the hard drive quit. There'd been no further warning beyond the occasional clicking/grating.

Don't wait.
posted by wryly at 11:57 AM on October 5, 2010

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