pulseaudio in gentoo

You have to emerge alsa-plugins with pulseaudio USE flags. Otherwise alsa won't be able to talk with pulseaudio and will seize the sound devices instead.

You also need a file /etc/asound.conf with the following content:

pcm.pulse { 
     type pulse 
 } 

 ctl.pulse { 
     type pulse 
 } 


 pcm.!default { 
     type pulse 
 } 
 ctl.!default { 
     type pulse 
 }

This file force alsa to use pulse instead of seizing the sound device for itself and its subordinate.