If you are using single coil pickups, they hum. If you are near a computer monitor, it causes more hum when it interacts with your guitar pickups. Yes, you can set your noise gate to stop the hum when you aren't playing, but the first time you start playing again, you will hear hum mixed with the guitar tone. You can minimize single coil hum by buying something like an Electro-Harmonix hum cancellation stomp box, or by buying noiseless single coils, or by replacing your single coils with stacked/mini-humbuckers that can fit inside the same body/pickguard cavity as your single coils, and then wire them in parallel/out of phase, which is still electronically humbucking, but sounds thin like a traditional single coil.
Short of the investment into new pickups or fancy wiring, you can try to move your computer monitor further away when you record, and lastly, use an old studio trick - FACE towards the West when you record your guitar parts with single coil guitars. No - I am not pulling your leg or joking at all. When you face WEST, it aligns the poles of the magnets in your single coil pickups with the North and South Pole, and makes them quieter. If you don't believe me, turn off the noise gating completely, turn on the volume of your guitar, and slowly turn in each direction. You will notice a sweet spot, where YOUR guitar is the quietest. It might not be the 90 degrees west, but it will be "westward". If you strap your guitar on, and you face West - it will be quieter than any of the other directions. Good luck.
