Audio not automatically working on the external device, using HDMI cable

[roberto]

When I connect my computer to the TV through an HDMI cable I'll keep getting the sound from the PC instead then from the TV, I have to go to audio plug and then select HDMI to make it work. I guess this should be automatic when I plug the cable, since that it's obvious in my opinion that I want the audio from the tv, if it's not according to you, at least there should be an option in the display plug itself.
And the same things is when I unplug my PC from the TV, the audio should automatically come back to the speakers, instead than keep being on HDMI.

In windows instead I get the audio in the TV as it should be as soon as I plug the cable.