1. The act of taking the vocalization of sounds and putting them in the form of the written word.
Onomatopoeiate (n), onomatopoeiating (v), onomatopoeiated (adj).
Used primarily to describe the sounds musical instruments make. For instance, the famous adult film guitar sound would be onomatopoeiated with the words "bow chicka wow wow" because that is a rudimentary description of the sound made by the guitar.
Animal sounds, suck as meow, bow-wow, woof, moo, and so on are also examples of onomatopoeating words.