Using an external modem also will allow you to switch the modem quickly to another computer. A person experienced at upgrading the innards of a computer can install an internal modem. Internal modems sometimes carry lower retail prices because the manufacturer doesn't have to supply a box. You may have noticed a screeching noise as you dial into your ISP and the two modems synchronize. It lets you know some action is happening.
Some external modems have volume controls to turn the sound down or off.
If not, sound levels from both external and internal modems can be controlled by software. Look for Settings or a Control Panel with a speaker volume control. Or, peek into the dreaded documentation. With call-waiting active, your modem may hang up when an incoming call beeps your phone line.