The process is by adding a command to the startup applications...
if you don't have the Gnome Login Sound you have to add this by clicking on Add button.
In there you have
for Name: add GNOME Login Sound
for Command: add paplay /usr/share/sounds/LinuxMint/stereo/desktop-login.ogg
for Comment: add Plays a sound whenever you log inthe Comment field can be blank but the other two are important.
above, but this give the opportunity to us to add your own custom login sound, I hope this was help full to you like was to me.