On 1920, when VOICE devices send audio with correct DSCP marking, just set trust mode on all ports connected to audio devices.(QoS , port priority , trust mode=dscp)
When your devices don't set proper DSCP markings, you have to go the hard way:
Create classifier, behavior, QoS policy, and apply this policy to VOIP ports.
imho , even the 500+ pages manual lacks proper documentation on this point.