From Halopedia, the Halo wiki
All Ears is an achievement in Halo 3: ODST in Halo: The Master Chief Collection. It is unlocked when the player finds 15 Audio logs in the campaign, alone or with another ODST. In the original game it is worth 30 Gamerscore and is represented by a blue square with audio lines going across it, with a 15 in the lower-right corner, and a picture of the Superintendent with his eyes wide open. In the Master Chief Collection it is worth only 5 Gamerscore represented by a sequence of images from Sadie's Story.
The achievement is awarded when the player unlocks their first terminal, regardless of which terminal in the hub that is. For terminal locations, see here.