The Japanese language has a lot of onomatopoetic words and yes they are also a part of the spoken language. I bet you’ve heard someone say ペラペラ right?
I recently read ガリガリ、ヒソヒソ、ギリギリ and どんどん. Some people think that onomatopoeia is the worst part of the language since there are so many onomatopoetic words and they can have multiple different meanings as well.
It’s reputation has been hiding in the shadow of kanji it seems.
There are even separate dictionaries available!