No, my voice does not change depending on my audience. Regardless if I am talking to an adult or a child, I don't change how I explain or refer things. I may address an adult with, yes sir, no sir, yes ma'am, no ma'am, but that is the only time my voice may change. If a child was asking to me to explain the game of basketball, I would explain it the same way as I would to an adult. Just because the age group you are addressing changes, doesn't mean the amount of knowledge you tell should.