Let's clear up some definitions.
You have a 1x4 HDMI splitter. You are splitting one signal to four destinations.
A SWITCHER switches multiple sources to a single destination.
It's not clear where you are trying to get audio from. If you are trying to get audio from the displays through their local apps into your A/V receiver, then you aren't going to do this through a splitter. There is no way to do this that way. Instead, you would need to connect the optical audio output from each display directly to the A/V receiver. This is by far the best solution.
If you are trying to get audio to pass-through the A/V receiver to the displays, then that's a different question completley.
ARC and HDMI is very simple. ONE TV - ONE A/V RECEIVER
Don't screw with that setup, and you won't have a problem.
OF COURSE if you have multiple displays hooked up it won't know what to do. Of course you would need a ARC enabled HDMI splitter to do what you want. It then would only work with ONE of the displays hooked up to it I expect because it wouldn't know which display to pull audio from.
It's a fairly complex setup that goes against the stupidity which is HDMI and ARC.
Just use optical.