Looking at the documentation for sound capture, it is only available for Windows. I have also checked the settings on my Mac and there seems to be an option for sound capture? How am I supposed to hear sounds from a remote computer then?
Unfortunately, sound capture is not supported in Viewer for Mac/Linux yet. However, we will definitely add it in our future updates. You can find the current list of all available features for Mac/Linux here. Sorry for the inconvenience.