Sound effects (SFX) are the non-music, non-dialogue audio elements that create the acoustic reality of a scene - footsteps, doors opening, vehicles passing, weather, environmental ambience, impacts, mechanical sounds, and any other sonic event that makes the world on screen feel physically real and present. They are a foundational component of sound design and contribute enormously to a viewer's sense of immersion in a scene.

Sound effects are sourced and created through several approaches. Location sound captures ambient audio during filming that establishes the acoustic environment of real spaces. Library sound effects are pre-recorded collections of categorized sounds that editors and sound designers draw from to populate scenes. Foley is the practice of recording custom sound effects in a studio by performing actions in sync with picture - a foley artist walking on different surfaces to create footsteps, handling props to create interaction sounds, or performing physical actions to create body movement audio. Sound designers also create and manipulate sounds synthetically for stylized, fantastical, or unrealistic sonic environments. The layering and mixing of these sources creates the complete sound world of a production.

AI audio generation tools are increasingly capable of synthesizing sound effects from text descriptions, enabling creators to generate custom sounds without recording sessions or library searches. In AI video production workflows, pairing generated visual content with appropriately sourced or AI-synthesized sound effects during post-production transforms silent or music-only footage into an immersive audiovisual experience, with the sound world reinforcing and deepening the impact of the visual content.