What Is An Onomatopoeia Used In Bud Not Buddy Chapter 2?

In Chapter 2 of "Bud, Not Buddy," the onomatopoeia "bloomp" is used to describe the sound of the horn on the "Jitney 49" bus when it stops suddenly. This Word is an example of how onomatopoeia can help create vivid imagery and bring a scene to life for the reader.