There are several potential sources for signal noise on electric or acoustic/electric guitars. These factors range from the wiring of the guitar to the specific amplifier that you are using. Most of the time the issue is just a matter of grounding and can be solved by using the ground-lift switches on your amp(s). Some acoustic/electric guitars also have a ground lift built in which can solve the problem too. Ultimately, some pickups, guitars, and/or amps just have a degree of signal noise they create and there may be little you can do to fix it.