Robert Kennedy's voice is rough due to a rare neurological condition called spasmodic dysphonia. This disorder causes involuntary spasms in the muscles that control the vocal cords, leading to a voice that can sound strained, shaky, or raspy. Kennedy has had this condition for decades, which makes his voice quiver and gives it a distinctive rough quality. Despite disliking the sound of his own voice because of this disorder, the condition itself is neurological and affects how his vocal muscles function rather than causing fatigue in his voice. Treatments like botulinum toxin injections have been used, but he has found them not always suitable for his case.