The letter AH is the 30th and final letter of the Tibetan alphabet.  It is counted as both a vowel and a consonant.  Its sound is inherent in all of the letters and unless a syllable has a different vowel added to it, the vowel sound is ‘AH’.  Its energy is considered neutral, neither masculine nor feminine.  The sound ‘AH’ has great esoteric significance.  It is considered to be the sound and vibration of an enlightened state of being.