No sound on computer
 

I installed debian and there is no sound coming, both from my laptop's loudspeaker and my headphone. What went wrong? I did a minimal install for debian 9

What did you try to make sound?

I play youtube video and sound file just to make sure

Then I doubt you installed minimal Debian. You must have some desktop software installed as well.

Most probably your desktop's sound processing is PulseAudio-based. Debian has a wiki page on PulseAudio that includes troubleshooting information. Though it was written for Debian 8, I am certain it's also useful for Debian 9.

ah i see now. XFCE doesn't come with pulse audio. What do i need to do?

The PulseAudio wiki page states
A web search might also help. xfce sound yields quite a few results.

search:
https://www.startpage.com/do/dsearch...nd+on+computer

The Debian Wiki has an article about Pulse Audio: https://wiki.debian.org/PulseAudio

It verifies that Pulse does not automatically come with XFCE or LXDE.

Nevertheless, the system should have Alsamixer. You could start by checking the alsamixer controls. See man alsamixer for more.

If you do install Pulse Audio, also install the Pulse mixer, pavucontrol; it gives you much more granular control than the simple volume control application. It's in the repos.

tasksel
 

you can try to use tasksel to install the bundle apps needed for a desktop, this way you can install whatever may be missing