flashplugin-nonfree-extrasound binary package in Ubuntu Xenial i386

 This is an open Source extension library for the Adobe Flash Player
 that enables support for otherwise unsupported sound systems. It
 provides the libflashsupport.so plugin. The sound system to use is
 automatically detected:
 .
  * It first tries to detect Esound,
  * Next, it checks for OSS.
 .
 If all of the above failed, it falls back to the ALSA driver that's
 built directly into FlashPlayer 9.
 .
 For PulseAudio support, look elsewhere.

Source package