When both PulseAudio and ALSA are available on the system, NoMachine configures its subsystem for using PulseAudio. All applications running inside a virtual desktop will use the PulseAudio sound system.

As a consequence when the node AudioInterface configuration key is changed to 'alsa', sound will not available inside the NoMachine virtual desktop.

A possible solution for using (only) the ALSA framework is to uninstall PulseAudio and all its components.

For example on Ubuntu use the following command to uninstall PulseAudio:

1) sudo apt-get remove pulseaudio

Then retrieve the list of PulseAudio components:

2) dpkg -l| grep -i pulse

and remove them one by one:

3) sudo dpkg --purge <pulse_component>

where <pulse_component> must be replaced with the name of each component listed by command 2).

E.g. if components are:

pulseaudio-module-bluetooth
pulseaudio-module-gconf

run:

sudo dpkg --purge pulseaudio-module-bluetooth
sudo dpkg --purge pulseaudio-module-gconf

An alternative solution could be to configure PulseAudio for using ALSA as explained for example here:

http://askubuntu.com/questions/294512/setting-the-default-alsa-device-for-pulseaudio

and on OpenSUSE:

1) sudo zypper remove pulseaudio

2) rpm -qa |grep pulse

3) rpm -e <pulse_component>