* The surface being slapped: A slap on a fleshy surface like a cheek will sound different than a slap on a hard surface like a table.
* The force of the slap: A gentle slap will make a softer sound than a forceful one.
* The object used to slap: A hand will make a different sound than a piece of paper or a cloth.
Generally, a slap can be described by these sounds:
* A sharp, percussive "pop" or "crack" This is common for a forceful slap on a fleshy surface.
* A dull "thud" This is more likely for a softer slap on a fleshy surface or a slap on a hard surface.
* A "whack" or "thwap" This could describe a variety of slaps depending on the force and surface.
There are also onomatopoeic words used to describe a slap, like "smack," "whap," and "thump."
Ultimately, the best way to describe the sound of a slap is to imagine the specific situation and try to recreate the sound in your mind.