It's possible, depending on the locale, that when the national anthem is played, it's bouncing off of the walls. During the medal ceremony for the men's 100 meter, it looked like our gold medal winner was fumbling the words but in reality, the music was echoing. I know that I was hearing a double version because it was in a stadium.
I saw the women's softball team and was glad to see some of the player's opening their mouths and whole heartedly singing. Most of our atheletes listen at first, then just sort of mumble the words, barely moving their mouths. Of course, those that do may be trying to control their emotions.
I liked seeing the olive wreath removed and placed over their heart also. During the women's long distance ceremony where we placed third, our athelete, took her wreath off and the gold medal winner from Japan? was singing her national anthem.