Файлы .wav из пакета skype-bin.
Вы можете попробовать переустановить этот пакет:
sudo apt-get install --reinstall skype-bin
У меня есть .wav файлы на в следующих местах: Ubuntu 13.04:
/usr/share/skype/sounds/CallBusy.wav
/usr/share/skype/sounds/CallConnecting.wav
/usr/share/skype/sounds/CallFailed.wav
/usr/share/skype/sounds/CallHangup.wav
/usr/share/skype/sounds/CallHold.wav
/usr/share/skype/sounds/CallRemoteHangup.wav
/usr/share/skype/sounds/CallResume.wav
/usr/share/skype/sounds/CallRingingIn.wav
/usr/share/skype/sounds/CallRingingOut.wav
/usr/share/skype/sounds/ChatIncoming.wav
/usr/share/skype/sounds/ChatIncomingInitial.wav
/usr/share/skype/sounds/ChatOutgoing.wav
/usr/share/skype/sounds/ContactAdded.wav
/usr/share/skype/sounds/ContactAuthRequest.wav
/usr/share/skype/sounds/ContactOffline.wav
/usr/share/skype/sounds/ContactOnline.wav
/usr/share/skype/sounds/SkypeLogin.wav
/usr/share/skype/sounds/SkypeLogout.wav
/usr/share/skype/sounds/TransferComplete.wav
/usr/share/skype/sounds/TransferFailed.wav
/usr/share/skype/sounds/TransferRequest.wav
/usr/share/skype/sounds/VoicemailReceived.wav