I had a similar problem. Had sound in mplayer and amarok and in firefox and opera with the mplayer plugin, but no sound in flash vids like on youtube. Occasionally when I would have sound on youtube I got the same loud “braaappp” at the start of each vid.
I used yast to uninstall pusleaudio, YAST>Software Management>(search for “pulse”) then check to “x” delete pulsaudio and it’s associated libs. Yast then installed esound as part of the package check.
Flash works now.