Sound in Gnome

[Ernesto Gonzalez Gomez <netogg@softhome.net>]

Hi,

I have a system with Gnome, and the sound is not working, I installed 
tkmixer, like a test, and with this mixer some applications works. Gnoise 
works, but there are not sounds for the system.
What I have to install or configure?

Regards,

Ernesto.