I am using a new Lenovo 23.8" HD monitor with my Mac Mini (late 2012) and i dont know what i should be setting the refresh rate at, can anyone help please? it IS working very well but sometimes i get a flicker from it.

I'm running a Mac mini (late 2012) with a Lenovo 23.8" monitor, the monitor is brand new. I'm running Mac OS High Sierra. Do I have a recommended/ideal refresh rate to be used?

It is working very well but sometimes I get the odd flicker.

Its connected via HDMI and since connecting the monitor I have a problem getting the Mac to play music on the speakers; it worked perfectly before, is it anything to do with being an HDMI connection to the monitor?