At the end of Mission 2: Welcome To The Jungle, you will leave a building and enter an area with very tall gras and Ceph Stalkers. Your Nanosuit will be jammed, and you get the secondary objective to disable the jammer. However, the objetive will not appear on your HUD. The jammer is just a little machine, located in the south-eastern corner of the area. Ignore the Ceph Stalkers, and run straight to the jammer. Press the jammer switch to turn it off and get the "Can You Hear Me Now" achievement. Note: You can also see a small world map with all objectives in the pause menu.