अः is considered as "swar" in hindi alphabet system(varna mala) it is pronounced like अह् (please note viram/halant) other than छः (chhah- six) (or may be a few more exceptions), it is ONLY used in writing Sanskrit words used in hindi. e.g. अतः प्रातः क्रमशः पुनः दुःख So, if you create a new word, u will write ह/अह only. In Sanskrit, this is a very important and heavily used. The question is good and I would not like you to misguide on pronunciation. Better to learn from directly from a master. For hindi, not needed.