Shut down all other programs on your computer that use the Internet while using magicJack. The magicJack uses your Internet connection to make and receive calls. If you are attempting to play a game or download a file at the same time you're trying to make a call, you may experience intermittent sound issues such as static or distortion.
Reboot your router and modem. Since the magicJack is dependent on your networking equipment to operate, any problems with these pieces of hardware could cause issues with the magicJack. Unplug your router and modem power cables and let them sit disconnected for one minute. Plug the cables back in and try to use magicJack again.
Adjust your firewall settings while using magicJack. Firewall programs -- like the kind that come natively installed in Windows or the type that come with programs such as Norton Antivirus -- can cause sound issues while you are making a call with magicJack. Either disable your firewall while using the device or select "Allow" when prompted by your firewall. The Windows firewall, for example, can be disabled through the Control Panel in the Start menu.
Plug your magicJack into a USB 2.0 port on your computer (if applicable). Though the magicJack will work with 1.0 speed ports, 2.0 speed ports operate faster and can transfer information at higher rates. This can go a long way toward improving the overall sound quality when using the magicJack.