Running Dissonance on iOS has no runtime dependencies.
In the Player Settings for iOS there are four settings relevant to voice chat:
Microphone Usage Description: You must enter the reason for accessing the microphone on the iOS device.
Prepare iOS for Recording: You must enable this setting to enable low latency audio recording.
Mute Other Audio Sources: You may enable this to ensure that background audio does not interfere with voice audio.
Force iOS Speakers when Recording: You may enable this to force audio to the speakers even when headphones are plugged in. If this is not enabled all application audio will be played through the call speakers instead of the main speakers as soon as recording starts.