The Audio section in a virtual machine's Settings window determines whether the VM will detect a connected sound card, and if the audio output should be played on the host system.
To enable audio for a guest, select the Enable Audio check box. The following settings are available:
Host Audio Driver: The audio driver that Oracle VM VirtualBox uses on the host. On a Linux host, depending on your host configuration, you can select between the OSS, ALSA, or the PulseAudio subsystem. On newer Linux distributions, the PulseAudio subsystem is preferred.
Only OSS is supported on Oracle Solaris hosts. The Oracle Solaris Audio audio backend is no longer supported on Oracle Solaris hosts.
Audio Controller: You can choose between the emulation of an Intel AC'97 controller, an Intel HD Audio controller, or a SoundBlaster 16 card.
Enable Audio Output: Enables audio output only for the VM.
Enable Audio Input: Enables audio input only for the VM.