Vroom

[2] It also describes the act of purposefully operating a motor vehicle at high speeds so as to create loud engine noises.

[3] The word is a common early childhood sound, and is used in speech therapy techniques.

Their phonological play would be the vroom sound of truck engines[7] Julia Gillen further elaborates in the book The Language of Children (2003) that "vroom" and similar sound noises are the earliest examples of speech development: However, you might look particularly at the accompaniment of words with actions.

Dennis M. Ruscello writes in the book Treating Articulation and Phonological Disorders in Children (2008):[8] The clinician should encourage vocalizations that can be carried out in the context of body movement or activity.

[8]"Vroom" is an example of a cross-linguistic onomatopoeia, in that its pronunciation and imitative qualities are consistent throughout many different languages.