can you please elaborate on the "bad grounding" reason, cause my car just started doing a humming/whinding noise three days ago, and it goes away substantially when i disconnect my subs, but i can still hear it when i have my windows rolled up, and i try roll them up more, i think its my alternator, my mechanic thinks its a timing belt pulley (he just changed the timing belt 2 months ago) and my uncle thinks its my cheap stereo picking up the noise from my engine/alternator and sending it thru the speakers... any input would be helpful... sorry about the long read