To earn this achievement, one has to find all 29 of the Audio Log locations throughout the "Mombasa Streets" portion of the campaign and the final Audio Log within the Data Hive mission. You will only be able to find the Data Hive location after you have found the previous 29 locations. You can do this on any difficulty, so you might as well do it on "Easy" so you can quickly take care of any resistance you meet on the streets as you travel. There are a number of maps of the Mobmasa Streets available online, some with linked video clips showing each Audio Log, and there are also complete video walkthroughs showing the locations of all of the Audio Logs, but there is not one place that puts everything together, including what to do if you have difficulty actually "retrieving" the Audio Logs.
First, you will need a good map. I like this one because it shows the names of some of the "flashback" missions of the campaign (i.e., Kikowani Station) that make it easier to know where you are on the map. I will caution you that the video on that page showing the location of the 30th Audio Log in the "Data Hive" level contains a "spoiler" with regard to the story that is told by watching and listening to all of the Audio Logs. If you feel you must watch the video before doing it in the game, I would recommend you stop the video once you see where the 30th Audio Log is. However, you really don't need to watch the video at all as once you reach the Marine who accompanies you to Level 9 in Data Hive, you won't need any further guidance.
I found this video walkthrough to be extremely helpful. It quickly runs through every location and even traces the route you will need to walk on the overhead map to reach the next location. If all of the Audio Logs are "retrievable" (see "Other Considerations" below) it should take you about half an hour to confirm that you have them all using this walkthrough.
Once you pick a map it is best to follow its Audio Log locations in sequence so you don't get lost. I had the map open on my laptop next to me while I played, but you can also print out the map and mark off each location as you find it. One initial thing to realize is that the Audio Logs do not need to be found in a specific order (but, see "Connection With Flashback Missions" below), though as you find them and listen to them, they will be sequential. This confused me at first since I needed to start looking for the 18th Audio Log after I went back to find all of the logs (I had found 17 while completing the campaign), and different maps labeled different locations as "18th."
Just remember that whatever audio log you find is the next one in terms of telling the story, so the numbering on the various maps showing all of the locations is really of no value except as reference within that map itself. Start with #1 on whatever map you choose, and go through to #29. Another thing to remember is that there is no connection between the "solo" and "co-op" campaigns as far as the Audio Logs go. If you find an Audio Log while going through the campaign on co-op, you will need to find the same one again if going through solo, and vice-versa. It's probably easiest to just do this solo, so you don't have to coordinate more than one person to all of these locations.
The biggest problem I had going through the streets to find these Audio Logs is that not all of them appeared "retrievable" when I found the correct location. You will know an Audio Log is retrievable by two clues:
- Virgil, the city's computer, will use the environment to clue you in that you are close. Police car lights will flash, crosswalks will operate, phones will ring, etc.; and
- The location of the Audio Log itself will be outlined in bright yellow if you are using your VISR mode. The Audio Logs are found in such items as pay phones, health pack stations, recruiting stations (in-game advertisements to join the UNSC--you'll know them when you see them) and a few others.
Connection With Flashback Missions
It seems that the availability of the Audio Logs to be "retrieved" depends on the completion of a certain number of the "flashback" missions. I believe the reason that not all of the Audio Logs were "retrievable" for me is that I had gone back through to certain of the flashback missions within the campaign in order to earn particular achievements. When you do this, your previous campaign progress is lost. As such, the game believes you have not completed any of the flashback missions after you begin skipping around.
With this in mind, if you have just beaten the campaign you should have no problem immediately going back to "Continue Solo Campaign" (though if your last save was within the Data Hive level this might not work) from the main menu and wandering Mombasa Streets to find the audio logs. If, however, you have skipped around after completing the campaign you will need to re-play the first three flashback missions in order to make all of the Audio Logs "retrievable."
I don't know the magic of the first three missions, but I found a post on the bungie.net forums that confirms my experience. Apparently five or six Audio Logs are retrievable after having completed the first flashback mission. Then after completing the second flashback mission, another 20 or so are retrievable. Completing the third flashback mission makes the last five Audio Logs available (the last five on the Mombasa Streets level), and then the last Audio Log is located within the final Data Hive mission. This apparent requirement of completing flashback missions is another reason to work toward this achievement on "Easy" difficulty.
Audio Log Story
The story that is told through watching all 30 of the Audio Logs adds a cool element to the campaign. You learn about some of the events prior to your arrival in New Mombasa, what and who Virgil is, and meet some interesting characters who provide a backstory to the campaign. The "spoiler" mentioned above relates to how the Audio Log story is tied to the main campaign story that you are playing. It is not something critical, but if you approach it without knowing how the two tie together, it is more satisfying. Once you have found the last Audio Log in Data Hive, listen to and watch it, then remember to look around and explore the room. Also notice the "condition" of the room and the area outside the room. Remember the events of the last several Audio Logs and you will see the connection.