GUITARS AND NOISE
Here is a frequently asked question: I am getting some grounding hum. When I touch the strings there is no noise, but as soon as I lift my hands off the strings or bridge, I get lots of hum.
What is described above in terms of things getting quieter when touching the strings is actually quite normal, and is evidence that the bridge is grounded. If you are holding any electric guitar/bass while NOT touching the strings, bridge, or control plate, you should expect some degree of buzz/hum, guaranteed. A relatively light normal hum will subside when you touch the metal, if your bridge is grounded. What is happening is the human body is functioning as a kind of power line antenna. Your body in close proximity to the guitar induces power line hum into the pickups. If your bridge is properly grounded, then touching the guitar silences the hum as your body is now shunted to ground. Many players at gigs simply get used to touching some part of the metal during periods of silence.
As indicated above, the level of this noise should be relatively light, so the primary concern with noise is "degree" or "severity". Therefore, the key questions to be asked here are what will exacerbate noise, and what can be done to improve the situation.
Line Noise - A very common occurrence is for any inherent guitar noise to be magnified by line noise (aka house noise). Line noise can be carried along with the standard AC current from wall into your guitar rig and can be exacerbated by playing near computer monitors, fluorescent lights, large appliances, and other things. So my recommendation is to test the instrument in different locations/houses and with different amps to rule out line noise (and make sure to test away from fluorescent light/computer monitors) and/or issues with the amp.
Single Coil Pickup Noise - Single coil pickups sound wonderful, but they will yield 60 cycle hum. If you are dealing with any line noise (as described above), then expect the 60 cycle hum to be magnified by it. To solve this problem completely, you would need to either switch to noiseless pickups, or employ the Suhr silent system. Shielding will certainly be helpful, but only to a point. Shielding is not a remedy for 60 cycle hum. It is a technique to manage the situation. That being said, I do highly recommend shielding your instruments, particularly if you are using single coil pickups.