I have a cheap LCD monitor (I-Inc) which works fine except for the speakers. There is an extremely annoying buzzing whining high-pitched hum coming from the speakers.
It stops when I unplug the audio jack from the monitor. It also stops when some things happen on the computer, such as when I open a new tab, strangely. After the tab-opening process (.5 sec) stops, the noise starts again.
Also, it does not stop if sound is muted.
My laptop also does not make this sound without the monitor.