People say this to me a lot too. I also have adhd and people say I get intense at times. Sometimes I wonder if it’s sub-conscious because when I am angry I do not stutter nearly as much. Also, maybe we sound that way because we are frustrated with our own stutter. If someone ask me to repeat myself, I sound so much angrier. As far as tips and tricks, perhaps slowly try to adapt your speech not to sound as aggressive or just so the basic tricks we learn in therapy. Putting H before each word or stuttering