Hi all, 
I am hearing very low level (but none the less maddening) noises from inside my computer coming through both speakers and headphones. The noises seem to be related to the computer "thinking", drawing windows, accessing discs and, most noticeably and reproducibly, mouse movement which causes a zipper like sound.
 
I have found a few similar references in searching "computer noise", "mouse noise", etc., but none of the situations seems quite exactly like mine. In particular, I would say that this is NOT the sound associated with "computer whine" and not I don't think it seems necessarily related to the video card but I could be wrong.
 
I have replaced the power supply and the main fan. I thought for a long time that it may be related to my firewire interface with a non TI chipset on MOBO. I put in a dedicated TI card and still had problem. Eventually I upgraded my audio interface from m-audio 410 to a Roland Octacapture (USB) and the problem persists. I know that this is not a Sonar issue because it is present when Sonar is shut down and I just have the computer on without even having a stand alone VSTi running. If the computer is off and I play keyboard (Kurz PC3X) thru the Octacapture stand alone the sound disappears (duh!) so I know for sure it is coming "from" the computer.Interestingly, but probably not surprising, the sound will disappear if I use the digital outs on the Octacapture to feed my monitors (JBL 4328's).
 
The computer is a 2 year old Dell with i7, 3 hard drives (1 is eSATA - no diff if that is disconneccted), video card is a 1Gb nVidea running two 24" monitors in HD, Windows 7 (aero is on). Avast anti-virus (makes no diff if turned off).
 
Hoping to find any ideas or advice. I am loathe to swap vid card only to find that is not the culprit but I will if I have too. Is there any way in BIOS to bypass the vid card? I think the MOBO has intel video chipset but not entirely sure about that.
 
Brian
 
 

And you've tried setting your Windows sound scheme in Control Panel to "no sounds" ?

Since using the digital outs to your monitors cures the problem I'd guess that your speaker cables are picking up electrical interference from the computer.

Check that the speaker cables are routed as far away as possible from the computer cables (eg video monitor cables) or maybe invest in some speaker cables with better shielding.

any of your audio tracks input monitors turned on with the input set to the on-board microphone???

Sounds like RF interference. There are a couple of things you can do. First - make sure your computer is grounded. Secondly - make sure the monitor cables have a rf damping "block" (and -if possible- the cables connecting to the USB and Firewire too). You can also use a rf blocking device in the power cables, but I think this wont work, because it is not external rf related. Third - make sure your computer power supply is giving enough output to feed all hardware. Some "cheap" power supply's are not up to par and can give this problems. At last - there could be a problem with the motherboard design. Some computers are great for gaming or office use, but not for music.

Have you connected a wire from the Octa-Capture ground connection to a ground point on your computer or uninterruptible power supply feeding your computer? You may need to experiment with where you connect the wire at the computer end. 

Also, with audio-over-USB I've often found that the USB port on a motherboard can contribute noise. I solved this by buying a PCI card with four USB ports. Anything with audio goes into there, while components like hard drives, mice, keyboards,etc. plug into the motherboard ports.

I was getting those noises when using the usb interface for my midi guitar setup, so I used the legacy midi and no problem.
There was a cure, like adding a ground wire or something but I never used it.

So you might try unplugging usb cables.

I notice I get the same thing when I plug in my usb player to load songs on it and it shares the sound system with the computer.

Thanks for all the responses! I had a bit of a "Doh!" moment this evening when I realized I have the Octacapture and JBLs hooked up by UNbalanced cables. It's not a long run but the Octacapture is rack mounted in the same cabinet where the computer is located. It is a tower design, just was convenient to put in the empty bottom of the rack, so the components and cables are in pretty close proximity. In fact, I think the problem became noticeable after I racked the Octa because I remember thinking , at first, that the problem was fixed, or nearly fixed, when I switched from firewire to USB. I don't have any long enough balanced cables to try out but I will be getting some very soon! Also will try grounding the Octa to the computer as Craig suggested (btw, I own the Octa thanks to your review Craig - and I have been very happy with it - much more versatile than my old 410 was!). I hope it isn't related to the MOBO USB (I had thought of that, but since the problem persisted after I switched the 410 to a separate FW card, I have been thinking it probably is not primarily a MOBO issue. But if above measures don't solve things I will be changing USB ports, looking for IRQ sharing with the videocard and adding a PCI USB card.
This is a busy work week so it may be a few days, but I will report back with results of my experiments!

Swamptooth,
I had never even seen those damping blocks until I bought a new home theater amp a few months ago. I've never had an RF problem that I noticed before. Do they really do much?

Tricky and not uncommon problem. I have even had a PC where this was audible through the earphone jack on the on-board sound chipset.
 
But from your description, it seems you have a ground loop. Either your computer or your interface should be earthed, but not both.

To test this, make up a short mains extension cable with no earth. Put it in line of your interface's or your computer's mains supply.

DO NOT GRAB THE METAL OF YOUR INTERFACE, RACK OR COMPUTER DURING THIS TEST.