How do you write out the sound of clearing your throat?

"Ahem" is widely popular. Depends how you hear it as.

"Ahem" sounds right to me after trying out a few options and seeing what they looked like. I then used "Ahem" in an email and it expressed just what I was looking for.

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"Harrumph" is the Word used for noisy clearing of the throat.

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It depends on what sound you are targeting and if it is really important that such be expressed. If you were writing for 'Scrubs' or 'House' certain 'clearing of the throat sounds' demand a chest x-ray while others don't.

Ahh... Ahh.. rouragraallaaa... arougraalural

means Heimlich manuever please!
Ahem