I think we get so accustomed to the trained voices of people in the media that when we hear an interview of an ordinary but extraordinary person like Peat and notice the difference we often assume something is wrong. When you are around the elderly you notice that the voice quality does change. His voice is comparable to others at least 10-20 years younger than his chronological age (imo). Most importantly though is the content of his speaking. Pure genius if you ask me. It may also be a bit stressful to be interviewed if you are not someone who enjoys the spotlight.