GW2 Sonic Periscopes can be found throughout the following areas – Diessa Plateau, Wayfarer Foothills, Snowden Drifts, Plains of Ashford, Iron Marches. Once you destroy the Sonic Periscope, search the Sonic Periscope Wreckage to collect Sonic Periscope Audio Log. On the map look for the Vigil Audio Log Collector and give him the logs. In return you will gain 100 karma. The periscopes reset daily. Locations are the same for all servers.
When you come close to the Sonic Periscope you will hear a strange sound like ringing in your ears, and your character will have a red circle aura.