Considering the importance of phonetic research over the last centuries and its role in familiarization with the language of Koran, this article has been selected and developed as the phonetic study of Surah Ar-Rahman. In this Surah, all the sounds are positioned in accordance with their needed place to such an extent the sounds cannot be moved elsewhere. Hence, when the description of heaven is given in Koran, soft and sweet sounds as in the phrase (Motakan Ala Rafraf Khezr) are used with phonemes such as “R” and “F” in that these sounds have this particular attribute. Likewise, when the Day of Judgment is described in Koran, it is possible to use glottal and strong sounds like the phrase “Eza Alsamaa Ensheghat” (إذا السماء إنشقت) and the letter “gh” has been used as the letter “qaf” invokes harshness and instability. Since the Qur'an is referred to as the book of human guidance, the study of the concepts and aesthetic qualities of this book is given increasing attention.