The Chromebox for Meetings bundle comes with a speakerphone that has both audio input and output capability.  However, you can configure it to work with other audio input/output devices, either USB-compatible or those compatible with a 3.5mm jack.  

From the Settings link on the Chromebox for Meetings home screen or the Settings icon inside of a video call, you can select the audio input or audio output device you wish to use.  Please note that the Chromebox for Meetings can use 1 audio output and 1 audio input device at a time.  It does not support having multiple audio input devices nor multiple audio output devices active.