Which of the following terms best describes the nature of impact sounds?

Impact sounds are characterized primarily as single occurrences. This means that they are typically brief, sharp, and often loud noises generated by an event such as a tool striking a surface, machinery being activated, or a door slamming. Unlike persistent noises, which continue over a longer duration, impact sounds happen quickly and are distinctly noticeable at the moment they occur.

While other terms like persistent noise and consistent frequency relate to sounds that are continuous or tonal in nature, impact sounds do not fit these characteristics. Additionally, a gradual increase in volume suggests a build-up that is the opposite of a sudden impact sound. Therefore, the term best capturing the essence of impact sounds is indeed that they are single occurrences.