In the area of Shantytown in Tomb Raider, you can find four strange contraptions just lying around in the open with cranks on them.
These machines are actually alarm sirens and if you interact with them, Lara will use her axe to destroy them. You need to find and destroy all four of these alarms to complete the Silencer Challenge in Shantytown. Here’s where you can find them:
Alarm #1: Coordinates – 712564, 3416086
Location. You’ll find this alarm on the bottom floor to the northeast, behind a fence overlooking the open area.
Alarm #2: Coordinates – 712596, 3416035
Location. You’ll find this one when you first climb up to the top of the catwalk that is south of the middle area. You can find the alarm on top of a roof sitting there beside a zipline.
Alarm #3: Coordinates – 712588, 3416050
Location. To the northeast of the center area, there will be another alarm that you need to destroy. Climb to the upper catwalk and you’ll see it across from the windmill.
Alarm #4: Coordinates – 712606, 3416060
Location. You find this on an upper level past the windmill, on a platform reached by running up a wall at these coordinates.