Blog of Michael Gimena

source : http://ubuntuforums.org/showthread.php?t=789578

1. Backup (and then delete) your previous configuration files:
Code:

$ mkdir ~/pulse-backup && cp -r ~/.pulse ~/.asound* /etc/asound.conf /etc/pulse -t ~/pulse-backup/
$ rm -r ~/.pulse ~/.asound*
$ sudo rm /etc/asound.conf

2. Ensure you have the necessary PulseAudio libraries and configuration utilities installed:
Code:

 $ sudo apt-get install libasound2-plugins padevchooser libsdl1.2debian-pulseaudio

3. Ensure the evil “libflashsupport” library is not installed:
Code:

$ sudo apt-get remove --purge libflashsupport flashplugin-nonfree-extrasound

And restart Firefox or Chromium  ^_^

I have tried this with my Ubuntu Karmic