Turn dial-up modem sounds on or off on Mac
If you hear beeps and other sounds when your computer connects to the internet, modem sounds are probably turned on.
On your Mac, choose Apple menu > System Preferences, then click Network.
Select your modem in the list at the left.
If your modem is not in the list, make sure your modem is connected to your computer (internally or externally), click the Add button at the bottom of the list, click the Interface pop-up menu, then choose Modem. Give your modem service a name, then click Create.
Click Advanced, click Modem, then turn Sound on or off.
Modem sounds can help you pinpoint problems with a dial-up connection by letting you hear whether your modem is detecting a dial tone, whether it is dialing a number, and whether the remote server is answering the call.