I stuttered badly through ages 7 through 13. I am 61 now and can still stutter and stammer. What I noticed, looking back, was a huge uptick whenever I experienced trauma which initiated the start of it to begin with. It would be almost gone and, suddenly, I could barely complete a sentence. It still crops up as stuck words now and then or stammering when I'm nervous or feel pressed or rush which also caused the pitch of my voice to rise. I learned to use a thoughtful pause instead of forcing out the stuck words or to pick an alternative word would often work. I also used and still use humor to dispel the awkwardness. Even holding my finger up to indicate "wait a sec" for dramatic effect helped me take control of the moment. If someone tried to say the word for me, I would say an alternate word or words as a joke. When I had to deal with stage fright while talking to a group, I would lead with the fact I stuttered, still can stutter, and still get anxious when addressing a crowd. So if my pitch changed or I had to do a thoughtful pause, I didn't have to worry about being humiliated. The pitch of yourvoice changing is tied to the stress or pressure you experience being different with different people. In my case, it could be caused by something as simple as a girl I liked flirting with me who seemed to be enjoying my visible awkwardness. Talking to a cop or a teacher giving me unwanted scrutiny, when I was a teen, was another time my pitch might have varied or when I was targeted and bullied in school. Looking back and even today, my effectiveness at speaking is always dependent on my anxiety level. Using deep relaxation and meditation techniques, paying attention to your anxiety and avoiding activities that raise your baseline anxiety is key. I know SOME speech therapists see anxiety and stuttering as separate issues, but they have never actually experienced what this is like. I can say, for sure, that anxiety and stress are a definite triggers for stuttering and the pitch of the voice rising. The worse the anxiety the more it effects us. It is heredity and my brother and daughter have drawn the same conclusions. Taking responsibility for our own improvement and comprehensive self care is key as is acceptance of our uniqueness. What people who are ignorant of this condition think or believe is completely irrelevant and frankly none of our business. Stick with your peers, especially people who have made real progress and/or accept and know a stutter is no indication of a person's intelligence. For every flaw, there is also a gift. The same thing that makes my daughter and I hypersensitive to stimuli, noise, and even ADHD and stuttering also gave her well above intelligence and empathy for others. Many people who stutter have above average intelligence and can often be excellent writers. As for the answer to your question, the voice always go up when people, any people, are nervous. How certain people perceive us, like when interviewing for a job or speaking to an authority figure, is more important and thus more stressful.