Comment 5 for bug 1643847

If I simply downgrade the package, it doesn't work.

I just manage to have the sound back with the following procedure:
#1 purge the package
sudo apt purge libpulsedsp pulseaudio libpulse0 libpulse-mainloop-glib0 pulseaudio-module-x11 pulseaudio-module-bluetooth pulseaudio-utils
#2 keep track of the additional removed packages, in my case
checkbox-converged checkbox-gui gdm3 gnome-control-center gnome-orca gnome-session gnome-settings-daemon gnome-shell gstreamer1.0-plugins-bad gstreamer1.0-pulseaudio indicator-bluetooth indicator-sound libasound2-plugins libcanberra-pulse libespeak1 libfluidsynth1 libfreerdp-plugins-standard liboxideqt-qmlplugin liboxideqtcore0 liboxideqtquick0 libqt5feedback5 libqt5multimedia5 libsdl-image1.2 libsdl1.2debian libunity-webapps0 qml-module-qtfeedback qml-module-ubuntu-components qml-module-ubuntu-test qml-module-ubuntu-web qtdeclarative5-ubuntu-ui-toolkit-plugin speech-dispatcher speech-dispatcher-audio-plugins ubuntu-desktop ubuntu-session unity-control-center unity-control-center-signon unity-settings-daemon unity-webapps-common unity-webapps-qml unity-webapps-service vlc webapp-container webbrowser-app
#3 reinstall the packages, with the pulseaudio one to the previous version
sudo apt install libpulsedsp=1:8.0-0ubuntu3 pulseaudio=1:8.0-0ubuntu3 libpulse0=1:8.0-0ubuntu3 libpulse-mainloop-glib0=1:8.0-0ubuntu3 pulseaudio-module-x11=1:8.0-0ubuntu3 pulseaudio-module-bluetooth=1:8.0-0ubuntu3 pulseaudio-utils=1:8.0-0ubuntu3 checkbox-converged checkbox-gui gdm3 gnome-control-center gnome-orca gnome-session gnome-settings-daemon gnome-shell gstreamer1.0-plugins-bad gstreamer1.0-pulseaudio indicator-bluetooth indicator-sound libasound2-plugins libcanberra-pulse libespeak1 libfluidsynth1 libfreerdp-plugins-standard liboxideqt-qmlplugin liboxideqtcore0 liboxideqtquick0 libqt5feedback5 libqt5multimedia5 libsdl-image1.2 libsdl1.2debian libunity-webapps0 qml-module-qtfeedback qml-module-ubuntu-components qml-module-ubuntu-test qml-module-ubuntu-web qtdeclarative5-ubuntu-ui-toolkit-plugin speech-dispatcher speech-dispatcher-audio-plugins ubuntu-desktop ubuntu-session unity-control-center unity-control-center-signon unity-settings-daemon unity-webapps-common unity-webapps-qml unity-webapps-service vlc webapp-container webbrowser-app
#4 Remove the user config file
rm -r ~/.config/pulse/*
#5 Shutdown the computer then turn it on again (don't reboot).
#6 Enjoy sound again :)