I'm using a hp dv4 running Ubuntu 11.10. The sound is fine when the speaker is on and the volume control works fine too. But when I plug in the headphones, the sound gets muted. Even if I change the volume to max, the indicator LED show's that its muted. Is this a bug?
I have the same issue (also on hp dv4 running 11.10, worked fine on 11.04). I just tried the following and it worked for me.
Go to 'sound settings' and click on 'output'. There you will see 'analog headphones' for the connector (at the bottom). Change that to 'analog speakers' and you will get sound on your headphones.
Strange, but it works.
In Kubuntu 12.04 after upgrading to Firefox 15 requiring an Adobe Flash upgrade I noticed several of my sound drivers replaced and removed without my authorization. I could use my speakers but when plugging in the headphones the sound muted.
I found the answer here after an hour of searching. Lots of Linux people just don't want to give a direct and simple answer about anything which really hurts the Linux promotion effort.
Go to the menu Settings -->
sub-menu System Settings -->
tab Audio Hardware Setup -->
select speakers in the connector pull-down -->
click button lower right Apply.
Your headphone plug ins will no longer mute the sound.
Installing the "crack of the day" alsa-driver code solved the problem for me.
I don't know if my problem was exactly the same as yours, but my headphone sound was very quiet, even when I cranked the volume to maximum.
Martin's workaround of going to the sound settings and switching output from analog headphones to analog speakers worked for me, but it was irritating to have to switch every time I plugged in headphones.