Re: PC makes USB disconnect/connect noise
Event viewer shows nothing in System or Applications. Device Manager has nothing with an exclamation mark but I shall keep it open for the next time I hear the noise to see if something is disconnecting and reconnecting.
I'm not using any beta drivers.
Re: PC makes USB disconnect/connect noise
Make sure to unplug anything connected to the USB ports except for keyboard and mouse then wait for any disconnection or connection sound whilst using it for a day or two. Then slowly add your USB devices one by one till one of the devices to make any sounds.
There is application developed by Nirsoft that view and give detail information about USB connected or installed to your machine:
http://www.nirsoft.net/utils/usb_devices_view.html
Re: PC makes USB disconnect/connect noise
See this page, there's some discussion in the comments. If it's an onboard Realtek NIC you can check the settings in Device Manager for it. Look at 'Power Management' tab, and then in Advanced - "Green Ethernet" and "Energy Efficient Ethernet". Try here too about keyboard/monitor child hubs.
Re: PC makes USB disconnect/connect noise
I had this recently so i used USBdeview to figure out what it was, turned out to be my corsair link system