you don’t need to install pulseaudio or alsamixergui, because alsa works probably good,
the problem is sound may be muted

run in terminal alsamixer and unlock (use keyboard M to mute/unmute) channels Master and Headphone or Speaker

check information about your sound settings, there are many diffrent methods:

cat /proc/asound/*
amixer scontrols

install volumeicon-alsa and run volumeicon
you can also install xfce4-mixer