The IPA symbols historically attached to these sounds are from the retroflex category. This hook may be interpreted as a reminder to curl the tip of the tongue into the retroflex position, or the arch position. Again, in Mandarin, these fricatives and affricates are all unvoiced. It is both unvoiced and unaspirated. The main difference between the two sounds comes from the tongue position, be it retroflex or arched, and the use of the lips, as to be discussed. Weather this is the tongue tip, as in the retroflex position, or the tongue blade, as in the arch position, is left to the decision of the singer. Whichever position is chosen, the frication which follows is done so by allowing that part of the tongue to remain close to the alveolar ridge and allow enough air to pass through, in order to create the turbulent airflow. Since both are unvoiced and unaspirated, focus should be primarily on the tongue position: in Italian, the tongue blade makes contact with the alveolar ridge to initiate the stop which begins the sound; in Chinese, it may be the retroflex or arch position.