Perfectimage: Yes, people who firmly believe that two things will sound the same are more likely to hear no difference between them. But I'm not saying," It can't be true because I can't hear it." What I'm saying is, the most plausible explanation for what you are hearing is that you become accustomed to the sound. If you want to present a more plausible explanation, feel free, but you have to do better than "that doesn't mean it doesn't exist." What physical changes take place in a wire after an electrical current passes through it, and how do those changes affect subsequent currents that are passed through it?