Dread Intrusion
From Halopedia, the Halo wiki
Dread Intrusion is a piece included in the Halo 3: Original Soundtrack. It plays during the level Floodgate, and includes the tracks Dread Intrusion, Black Tide, and Old Friend.
The middle part of the piece (Black Tide) is a remixed version of the song Ghosts of Reach from the Halo 2: Original Soundtrack.
It runs for 5 minutes and 25 seconds.
At around 0:50, a reversed message can be heard. The voice sounds and echoes similar to the Gravemind. It says Side by side, we march as one. Humans and Elites will die. The Earth will fall if we strike together. So forth shall all of life.
