Hello, I just purchased two of these monitors to replace Apple Cinema Displays on a MacPro system. The GPU is an AMD Radeon HD 7970. Each monitor is connected with a 4K cable with mini DP on the GPU end, and DP on the monitor end. I have also connected the USB cable Dell provided from a USB port on the computer to the "upstream" USB port on the monitor.

My question is WHERE does the audio come from on this monitor? Does it or can it come on the USB cable? The DP cable? Or, do I need a third separate audio cable from the "audio out" on the MacPro to the "audio in" on the monitor?