How do I change default ringtone in Skype?

How do I change the default ringtone in Skype? In some old versions I was able to replace the sound files in the /usr/share/skype/sounds/ Now the Skype folder [on my system] is /usr/share/skypeforlinux/, but I can not find any sound files there! They are not in the /usr/share/sounds/, either The default file ***was*** named CallRingingIn.wav My system is Linux Mint The default ringtone is nerve-wrecking and soul-killing Thanks!