Is this possible with the dynamic lighting?

I used dynamic lighting last session as a test for the players. I set vision to 120 degrees-what I felt was a decent vision for the players. However, a couple of players had an issue-with sound. Namely, one character was talking to another from maybe 20 feet back, but that player had no idea where he was since he couldn't see him. They wanted me to open up vision to the rear to represent hearing. I don't want to do this for certain reasons in the next dungeon that I won't specify in case they end up seeing this topic, but needless to say, opening up vision to the rear would completely ruin my  idea. So is there something I can do with dynamic lightning to maybe give a shorter vision range or something, maybe 10 feet instead of 60 to the rear? Failing that, any ideas on how to tackle this issue, aside from always saying "you hear something behind you"?

I have found that I needed to give my players 360° vision to stop them from rotating their tokens constantly. While it is not realistic, neither are dragons or spaceships. If the characters are using a directional light source I do limit it's angle, but the "vision thing" is a tough one, it is only a matter of time before your players discover the rotation trick, and you will have to look at whirling dervishes for the whole game.

I was actually ok with them rotating in place to see around themselves-represents the person taking the effort to look around. It was actually one of THEM that didn't like my suggestion, saying it would get annoying having to do that.

I don't have capacity to write this right now, but you could have a script which gives each character token a little transparent follower with 10' radius 360 degree vision. If the follower is controlled by the player, then they'll see it's vision as well as their own. Then the character tokens could keep their longer radius 120 degree vision. It'd be a little weird, but it should work. There might already be a follower script which you could use for that purpose.