This is absolutely correct. The noise that you've described, while undesirable, can be totally normal. Many people think that you have a grounding issue because when you touch the strings the noise goes away - the strings are being grounded to you when you touch them. THAT IS THE EXACT OPPOSITE OF WHAT IS HAPPENING WHEN THE NOISE GOES AWAY WHEN YOU TOUCH THE STRINGS. There are signals flying through the air all day every day. Your body is an antenna for these signals. When you're not touching the stings or another metal part these signals are more likely to be picked up by your pickups due to proximity if not shielded. When you DO touch the strings, these signals that your body is picking up are being sent to ground and not able to be picked up by your pickup. Does that make sense? If the noise is intermittent it could be caused by another electronic component in your home. Mine is louder when my wife watches TV in the next room. It could have to do with the direction your facing. I'm not assuming that you do not have a ground issue. I'm just saying that do not be surprised if there's nothing that you can really do except shield/ground your cavities.