No Audio for Acer Aspire 5920

[Black Sun]

I have Acer Aspire 5920 with Ubuntu 9.04 - the Jaunty Jackalope - installed, earlier there was no problem of audio but recently it all stopped working and there is no sound in movies , music or any other notification sound. I am completely new to linux so I have no Idea of what is to be done, please help.

[Diphallia]

Try going to System>Preferences>sound.

First check if sound is muted. If it is, just unmute it.
If it's not muted go to the "Hardware" tab and check which sound card is enabled.

[Black Sun]

ok, I did what you asked, it wasn't mute but "line in" was off, I turned it on and now it works fine but there is still a weired buzzing noise at the startup rather than it's login-sound...

any solutions??