Each Oculus hardware platform has different audio capabilities.
The Oculus Rift has a built-in DAC (audio over USB connected to the headset) and ADC (for microphone). The audio subsystem is class compliant and supports Windows, Mac, and Linux. The HMD has integrated headphones and a microphone.
The Mobile devices support 16-bit, 48 kHz sound. Headphones can be used, but aren’t required.
Mobile performance is significantly lower than desktop PC performance, so try to minimize the number of audio sources.