You may be tired of system beep ,or you just want to change your ubuntu login/logout sound effects,and I will tell you how to do it easily in this tutorial.

First,open up the sound preferences at System–>Preferences–>Sound


To disable system beep,click on Sounds tab and untick Play alert sound


For login or logout sound effects,at Alerts and Sound Effects box,find the line and click on Default,select Custom to change it in menu.