Why does my computer (Mac OSX) grumble when it's working?

Hunger pangs? Bad hair day? Wants to go to the beach? Osteoarthritis?

What’s the actual machine? Desk top? Lap top? How old?

Which OS? The latest is 10.8.4, I think. Or it was a minute ago.

It may be the hard drive getting ready to kick the bucket. That’s the movingist piece inside. You may want to consider backing things up.

Another possibility is the fan. That also moves.

and hey from ABQ, Susan!

Most computers make these kinds of noises. There are scary strong magnets in them that spin & that’s usually what people hear.

It is the hard drive. Generally, if you notice the sound getting worse then it is time to make sure you have a back-up (which you should do even if the drive works perfectly). You can get a external USB drive for 60 bucks. It is trivial to make a clone of your internal drive onto the external that you can boot from over USB. Really, five mouse clicks and a hour of waiting and you will have a external drive you can boot from.

That way you can use the external if the internal dies until you can replace the internal one. And once a new internal is installed you can just clone it back and it will be just like it was. A cheap insurance policy if you ask me.

This is super easy to do and I could walk you through it. Or with screensharing in iChat/Messages I could do it for you while you watch. Send me a PM if you need more info.

I’m guessing it’s the exhaust fan. My old computer had a similar intermittent “grumbling” noise. With the case open, try tapping (gently) on the fan and see if the noise stops. If so, it’s the fan (bearings can go bad.) If not, it’s probably the HDD as @johnpowell says.

@rexacoracofalipitorius :: I believe she has a iMac or MacBook. Neither is really easy to get in and check the fans. It would be prudent to get a back-up going ASAP.

And really, that goes for everyone. I have had hard drives die for no reason that I could figure out. No noise, no nothing. They just stopped working. They will fail and all your pictures, movies, music, and documents will be gone. It is so cheap to keep a copy on a USB drive that everyone needs to do it. We are talking 50 bucks here.

Open activity monitor app and
Looks at the disk info graph. Then try opening several apps at one, copy a file, etc. Does the clicking sounds increase or decrease in response to activity on the graph? If so, it’s probably your hard drive and you should back up your data immediately. If the sound is more constant and doesn’t correspond to the graph activity, it’s most likely your fan.

@johnpowell is 100% of correct. Do a backup NOW. Not just OP but everyone. (But not me, cause mine goes automatically- though I did just check the log. Rsync FTW!)
If you don’t have a current backup, do that BEFORE you do any further diagnosis.

All: I did a backup. Thank you all very much, especially the great immortal johnpowell.