Every time I load up the campaign I can hear the music and sound effects but never any of the characters voices. This includes cutscenes as well as during the missions.
Try this fix: https://www.reddit.com/r/xboxone/comments/7e7rl5/tech_halo_5_xbox_one_x_audio_issue/
If you don’t want to have H5 in English, then there is no fix that I am aware of.