On this page of our guide to BioShock Infinite you will find the third part of a detailed walkthrough of Chapter 31 - Memorial Gardens. The last tear is in a photo studio where you can also find a voxophone and some loot.
After you've left the bank begin your journey to the Photo Studio (point number 5 on our map). Once you're there ask Elizabeth to open the door and enter the studio. Explore this entire location before opening the last tear. There are some items at the back of the studio, including a new locksmith's set.
Once you're ready open the tear, listen to its "content" and collect Voxophone #68 that will appear in its place.