The purpose of having letters that represent both voiced and unvoiced sounds in a written language is to accurately represent the spoken language. Languages often have pairs of sounds where the only difference is the presence or absence of vocal cord vibration, which is known as voicing. For example, in English, we have pairs like "p" and "b," "t" and "d," or "s" and "z." The distinction between these pairs is crucial for conveying meaning and understanding spoken language.
By using specific letters to represent both the voiced and unvoiced versions of sounds, we can convey the intended pronunciation and differentiate between words that would otherwise sound the same. This helps ensure clarity and comprehension in written communication.
Additionally, having letters that represent both voiced and unvoiced sounds allows us to analyze and study the phonetics and phonology of languages. Linguists use these letters to describe and categorize the sounds of a language, which helps in understanding its structure and patterns.