To see the bug,you can build a nether portal.Then set your gamemode to survive or adventure.Walk to the portal and walk through.Just need to pass by and not to wait to be teleported to the nether.Or you can walk into it and walk out immediately to avoid being teleported to nether.Then you will hear a sound in about 3.5 seconds.In normal situation,the sound can be heard when you are standing in the portal,waiting,and being teleported to nether.But the sound do not be writen out even you turn on subtitles.

Maybe you need to turn up the sound of your computer to hear.Maybe the background music will affect it.

Thank you very much.