You can set a default ringtone for all incoming FaceTime audio and video calls and phone calls on your Mac, and change the ringtone or text tone for individual callers.
Change the default ringtone: Choose FaceTime > Preferences, click Settings, click the Ringtone pop-up menu, then choose a new ringtone.
Change the ringtone or text tone for a caller: Edit the caller’s contact card in Contacts. For more information, see Make changes to your contacts.
When you select a new ringtone or text tone, a preview of it plays unless your Mac is muted.