If you are used to work on Ubuntu terminal extensively and when you type initial letters of some commands on terminal and press TAB to type the rest of command, when there are more similar commands present, you will hear the TAB press sound ( i.e. terminal alert sound ) on Ubuntu.
This may be good sometimes, but when working frequently on terminal, you may irritated with this alert sounds. So we preferred to disable this alert sound by following below mentioned steps..
Open the “Settings” from Activities or you can open Settings from top right corner as well.
From settings, go to “Sound” -> “Sound Effects” tab and reduce the volume if required or turn OFF the “Alert Volume” as shown in below image.