Simple:
* Ahem
* A-hem
* Ahem!
* Hm
* Hrm
Descriptive:
* A deep, guttural 'ha'
* A raspy, clearing sound
* A loud, rasping 'clear'
* A sharp, short cough
* A throaty 'harrumph'
* A strangled 'uh-huh'
* A rattling sound, like a dry leaf caught in the throat
Onomatopoeia:
* Rrrr-r-rrr
* Kh-kh-kh
* Hrrrk
* Chchch
The best option will depend on the context and the effect you're trying to achieve. For example, if you're writing dialogue, you might choose a simple "Ahem" or "Hrm" to indicate a brief throat clearing. If you're trying to create a more vivid and descriptive scene, you might use something like "A deep, guttural 'ha' that echoed through the room."
Ultimately, it's up to you to choose the sound that best fits your writing.