Light buzzing from laptop when trackpad touched - help?

I have a new HP Envy 4 and have just noticed that, whenever I touch the trackpad (one touch or scrolling), a light electronic buzzing sound can faintly be heard. It's not coming from the trackpad itself, but from the body of the notebook (under the keyboard), and sounds not unlike a normal computer processor noise. Always stops when I take my finger off the touchpad. It's not massively loud, noticeable in a quiet room. But it is a little annoying. Is this unusual? Should we expect absolute silence from our touchpads?

 

Do you hear it both on battery alone and on AC adapter? It's usually a common ground loop signal that causes the minuscule hum.

 

electronic? through the speakers? more of a vibration caused by electronic components?

this is important. i mean, as important as any buzzing could possibly be.

 

I hear it both when running the laptop on battery and using the adaptor. I've been told variously that it 'could be normal' and that it 'shouldn't be happening.' It's only audible in a quiet room. What is the 'common ground loop signal' you mention? The buzz occurs at every touch of the touchpad, and stops when I take my finger off it