Vocal repeater
From Halopedia, the Halo wiki
The Vocal Repeater is a piece of UNSC technology that allows for unimpeded conversations, specifically while two people are listening to different kinds of music, yet simultaneously having a discussion. While it is mentioned that no matter what, "...conversations...continue uninterrupted..."[1], it is currently unknown how the repeater is able to distinguish vocalizations from background noise.
A Vocal Repeater was available in the stock model of the 2553 Civilian Warthog.
