What type of sound is categorized as a sound effect?

Sound effects are essentially any non-verbal auditory elements that enhance storytelling, create atmosphere, or add realism to a scene in film and video. The category of sound effects includes a wide range of audio elements like footsteps, doors creaking, cars honking, and any other ambient or distinct sounds that contribute to the overall auditory landscape of the project.

The correct choice encompasses sounds specifically created or captured to support the narrative rather than being composed music or spoken dialogue. While music tracks and dialogue from actors play vital roles in storytelling, they fall into separate categories in audio post-production. Music is often used to evoke emotion or highlight themes, and dialogue conveys the characters' voices and interactions. Background sounds are also distinct as they usually provide a sonic backdrop but don't necessarily focus on enhancing specific storytelling points as sound effects do.

Thus, the correct answer highlights the broader definition of sound effects as anything outside of music and dialogue that enriches the viewer's experience and assists in conveying the story's emotions and setting.