Calvin has a higher pitched male voice, his voice tends to waver from high to medium just during a normal conversation. His voice is very animated and usually over exaggerated, he's the comic relief of the series you might say. 

Later in the series Calvin undergoes serious depression and mood swings, if these things trigger you, please do not audition.

Backstory : Calvin grew up a trickster and a bit of a know it all, he was very smart, but never let anyone know it. Calvin is a very comedic fellow and tries to make anyone and everyone laugh given the chance, Calvin struggles with a split personality disorder which is found out in Season 2. He can either be very comedic and happy, or angry and when he snaps and becomes angry, he loses all sense of fear. He also learns to cope with the disorder, and in the end learns how to keep it under control. His parents always favored his brother Eric, the oldest, and Calvin has resented him for it all his life.