An electric guitar has an advantage over acoustic guitar that when you play it unplugged, it will definitely sound low. They are not going to be silent, but you will feel the difference. You certainly don’t need any fancy gadgets if you wish. Just take a soft towel and place it under the strings as close to the bridge as possible. It will dampen the sound down significantly. You can also block the soundhole of the guitar by shoving something in. Apart from that, you can also tie a soft material close to the neck.