What is UAC?

The USB
audio device class (also USB audio
class or UAC) is a USB device class that describes
devices capable of sending digital music via USB connection, such as
microphones, speakers, headsets, telephones, musical instruments (USB audio interface or USB analogue
converter -USB DAC) , etc

The USB working group has published three versions of audio
device specifications : Audio 1.0, 2.0, and 3.0, referred to as
"UAC" or "ADC"