On this page of our guide to BioShock Infinite you will find the first part of a detailed walkthrough of Chapter 23 - Bull Yard. In our guide we have included information on how to get to the Graveyard Shift bar and where to find 2 new voxophones. On the way to the bar, it is best to avoid any ongoing fights.
Exit the impound and you'll notice that Vox forces are fighting here with the police units. You don't have to participate in this battle, especially since reinforcements will continue to show up as long as you don't leave the yard. As a result it's best not to waste time and resources on pointless combat. Instead use the sky-lines to quickly get to the other side of the square.
Use the well-known path leading towards the Graveyard Shift Bar. You'll notice several Vox taking pictures in front of a defeated Handyman. Make sure to examine this half-man, half-machine to uncover Voxophone #48.
Go inside the Graveyard Shift Bar. There's a Voxophone #49 on the bar's counter and once you have it return to the elevator to travel back to the Plaza of Zeal.