Michael is very closely related to the Master Chief in how is characteristics are. He's somewhat withdrawn, not big on socialization, but is amazing in the field. His voice is similar to Chief's, but a little more gravily.

EDIT: In both lines, Michael is talking to Ben, first explaining the fortifications of the base, so he's still very collected and calm. He's speaking clearly. In the second, he's slightly more panicked, because he wasn't expecting the leader to be coming out of the garage with a group. However, he's still collected and speaking clearly and sharply.