We have covered this scenario in a number of discussions. The problem is that the hdmi port on the Arc is expecting an eARC audio input. At the moment there are no hdmi Switches and splitters in the market that can mimic an eARC port as would be available on a TV. If you connect a standard hdmi audio output from a uhd player for example to the Beam (also uses ARC) you would hear no audio as the ARC looks for audio input on different pins on the hdmi cable). That’s how I understand it anyway. 
 

it may be possible if you could source an hdmi lead that transposes the hdmi audio from your splitter to the hdmi pins used for the audio input of the ARC port on the beam. Unfortunately I have not found a cable to do this so I can try it out.