Random Error noise

The noise is actually device connect and device disconnect. It happens randomly and goes on for several minutes. There are no external devices connected. If I look at the Device Manager tree it refreshes with each noise. And I randomly get the error message "USB device not recognized" but it does not necessarily occur with the noise.
My computer is a Dell Inspiron 14z Windows 7 home premium 64 bit.
I've updated all drivers and unplugged the computer and let the battery run completely down.
I've searched the forums here and none of the discussion on similar subjects have helped.
Thanks for any input.

Hi, have you got a card or a blanking plate in SD card reader - this was making my wife's laptop think that something was connected/disconnected, removed the SD card blanking plate and now its ok.

Thanks I'll give that a try when the noise starts again. Since I've posted it's been mute. Go figure.

The noise came back this morning I popped the SD blank out but the noise continued.
Is there any way to search while the noise is occurring for the cause? Like what program or device might be active at the same time?

Well, the noise is back but as I was getting ready to write this post I moved the screen on the laptop and the noise stopped. Any new ideas?

Here's a couple of threads you can work through to see if you can find the cause.
This seems like one of those issues where several people have the problem, but there is no universal answer.

Device Connect and Disconnect Sounds Play When NOTHING Is - Microsoft Community
Random Device Connect / Device Disconnect Sounds - TechRepublic

Thanks for the links DavidE. I'll try shutting off wireless next time. I've tried sliding the dummy SD card in and out. Maybe that helped, I did not have the sound today, yet. It isn't any USB device I have connected because I don't have any connected. But I do periodically get the "Unknown USB Device" error flag.
Like I said I have updated all my drivers.
I mentioned before that when I move the screen back and forth (laptop) it sometimes stops?
Can the screen connection be the problem ??

I have a desktop and when i turn on and off the monitor i hear connect / disconnect sounds.

I would GUESS if your screen is disconnecting/reconnecting when you move the screen you would see it flicker ???
I wonder if moving the screen could be causing some other connection to disconnect/reconnect ???

I just turned off and on my monitor, and heard the sounds.
I looked in Event Viewer to see if anything is logged, i couldn't find anything

Thanks for the response. I don't think the screen flickers. I'll have to pay closer attention

The noise made a short appearance this afternoon. The screen did not flicker. But the "Unknown USB Device" did come up.