. Computers and phones put out a lot of electrical noise. Check all the shielding in the guitar. Start with shielded cable from the volume pot to the jack. Twisting the wires does nothing or we'd all use a twisted pair from the guitar to the amp. I have two identical LP HH guitars, both fully cavity shielded and jack wires are shielded cable, but the one without covers has a lot more noise than the one with covers while trying to record next to the computer. You can test if this is the problem by making a 'tinfoil hat' for your pickup(s) and running a ground wire from them to the jack ground or guitar cable outer grounded case at the jack. Lift and replace the ground connection and you'll know if that is the issue. Be careful not to damage any pickup winding wires or short out the pickup connections or it will be really too quiet... .