The Seed syllable āḥ is associated with Amoghasiddhi and the karma family. It is the long ā with the visarga or aspiration mark. The pronunciation of the visarga is usually described as a soft echo of the vowel. As well as appearing on it's own āḥ occurs in the set of syllables: oṃ āḥ hūṃ.
Pronounced /aːh/ (IPA)
oṃ āḥ hūṃ
The syllables oṃ āḥ hūṃ as a set are associated with body, speech and mind.