Student or Learner
Another instantly communicable facet of a person's conversation is the degree of loudness employed. We assume, perhaps correctly in the majority of instances, that extroverts speak louder than introverts, though this is not always the case. Also, men tend to use more volume than women. A person speaking softly might be doing so for any number of reasons - secrecy, tenderness, embarrassment, or even anger. People who are deaf tend to shout because they overcompensate for the lack of aural feedback they receive. And foreigners often complain of being shouted at by native speakers. Oddly, the latter must suppose that speaking loudly will somehow make up for the listener's apparent lack of comprehension.
What does this "must" mean? "obligation" or "strong presumption or certainty"?
I am not a teacher.