Paralanguage can be very significant such as voice quality and other vocal effects (whispering, laughing, breathiness etc) alongside non verbal behaviour (eye contact, facial expressions etc)
Sometimes writers (likely comic book writers, users of communication tools etc) will try to suggest sounds by manipulating conventional written alphabet
1991 Oxhana- a girl raised by dogs and could speak human words (however for the first three years of life she was raised in a domestic setting and exposed to language)