When someone is talking to you, it's common to periodically encourage them with minor expressions of agreement or sympathy like nodding, raising your eyebrows, or even saying "hm" or "mm" or "uh huh". When speaking at length, it can be disconcerting not to get these little encouragements, and it's usually a sign that the listener doesn't care or isn't listening.
Today I listened to an interview on the radio. It was perhaps the most frustrating hour of radio I've ever experienced. The interviewer kept interjecting quiet little "hmm" and "mm"s every ten seconds or so while the interviewee was speaking, and I found it extremely distracting. There was just enough time between these utterances for me to get back into what was being said before the next one would yank me out.
A friend of mine explained to me recently that there's more to cinematography than just pointing a camera, because the frame rate of film is so low that certain kinds of subject motion just don't work with our vision. To avoid visual badness, certain kinds of shots are just not done. Then I saw a documentary that clearly illustrated what can happen when these shots are not avoided. It really made me appreciate the craft of cinematography. Today I have a greater appreciation for a good sound editor.