How do you know it's Voles? The critters could be Moles or even snakes for that matter. Even skunks can't be ruled out.
The first suggestion is to visit the Nursery or Home Center, and start reading the 'bags' of Killer Products on the shelf to see which product BEST describes what you're seeing in lawns. For example, both Moles and Voles dig tunnels but Moles (I think) leave 'volcano-looking' entrances. In short, if you can rid the area of the lawn in question of the critter's food source, they'll leave to find a new source.
I've read that things like Castor Oil mixes and 'sonic vibrators' don't work, so stear clear of those ideas (unless you've tried EVERYTHING else and are desperate. Then, you have nothing to lose.) Visit Google.com and start reading. From there, go to the Store(s) and see if you can find something to help.
My best to ya and hope this helps.
Jay J -Moderator