In college, I had a teacher, Douglas TheWhisperer (not giving the real last name intentionally), who would start talking in a normal voice or may be little louder and then his voice would gradually go down to whisper and around the end I wouldn’t hear anything he was saying. I am pretty sure other people had the same problem. Out of respect and fear (he had the power to give me any grade) I never told him about it.

Many days he would come to classes and say “I will let you go early today”. However, he would actually end the class at the right time or even late. After 2/3 classes I stopped paying any attention to his “letting early” speech. However, he was (hope still is) a good person and it was easy to get an A in his class.