$ sudo apt-get update
$ sudo apt-get install flashplugin-nonfree-extrasound

flashplugin-nonfree-extrasound is installed in your system.

Make ensure the flashplugin-nonfree-extrasound package were installed using the commands given below,

$ sudo dpkg-query -l | grep flashplugin-nonfree-extrasound*

You will get with flashplugin-nonfree-extrasound package name, version, architecture and description in a table

flashplugin-nonfree-extrasound package basic information: