In the context of motion pictures and television, sound effects refers to an entire hierarchy of sound elements, whose production encompasses many different disciplines, including:
Hard sound effects are common sounds that appear on screen, such as door slams, weapons firing, and cars driving by.
Background sound effects are sounds that do not explicitly synchronize with the picture, but indicate setting to the audience, such as forest sounds, the buzzing of fluorescent lights, and car interiors. The sound of people talking in the background is also considered a "BG," but only if the speaker is unintelligible and the language is unrecognizable. These background noises are also called ambience