Dual PC Streaming and audio Setup
For the audio setup, you must set the capture card as the playback device on gaming PC so that the audio can be captured in the software on the streaming PC.
There are two ways to fix the gaming PC without an audio problem because the audio has been transmitted to the streaming one.
The first one, you can connect the HDMI from the HDMI out port on the capture card to your gaming monitor if the monitor has a built-in speaker.
The second one, you need a virtual audio software to duplicate the audio on your gaming PC,
you may refer to the link below to download and set up the software, thank you.