Definition: USB audio

The transmission of audio signals via the USB interface. Using IN and OUT commands and four transfer modes, audio and audio control signals are sent in USB frames from a host device (computer, tablet, etc.) to speakers and mixing equipment and from a microphone to a host device.

Modes: Bulk, Isochronous, Interrupt and Control
"Bulk" and "Control" transfers send audio data and control commands without errors, while "Isochronous" mode is a real-time transfer with no time to retransmit. The "Interrupt" mode is a polling method that checks the status of the host; for example, "is the Mute button pressed?"