Onomatopoeia (just to save a trip to Merriam-Webster's site) is the use of words that attempt to reproduce the sounds they represent. For example, the 'gurgle' of a stream or the 'buzz' of a bee.
My personal favorite is 'slurp' - the sound that's made when you're attempting to empty a cup of beverage with a straw!
I believe it is proper and even desirable to use onomatopoeia when writing. However, it may only be suitable for certain types of writing. For example, it may be inappropriate to say "the control subject squeaked when injected with solution A" on your PhD thesis!"
The power of onomatopoeia is undeniable. Why else would children's books contain so many of them (This is a cow. The cow says "moo")? Toddlers who are in the early cognitive stages can easily relate words to sounds with this method and so it's an effective way to teach those and, subsequently, non-onomatopoeic words.
In fact, it's a pet theory of mine (and perhaps others too, I'm certain) that this is exactly how human speech began. Man started imitating natural sounds, which he could later reproduce to convey messages about those objects in their absence. For example, "woof woof chomp chomp plop plop" could have meant: "The dog's eaten his dinner and done his duty." Easy!
While it may be a good idea to use this device to help readers relate to a sound in your mind, don't use it excessively. There are other "sophisticated" ways of expressing sounds, such as the lowing of cattle (rather than mooing), the grunt of a pig (rather than 'oink'), etc.
Written language today can seem dry and boring because we have so many alternatives to express ideas - doodles, images, sounds, smileys, texting styles, animation, videos and many more. This poses a challenge because writers sometimes have to write at a sub-optimal level just to be understood by more people.
If you can find the right balance when using onomatopoeia, you've 'whacked' the nail right on the head. Good luck, Steve!