Definition of sound effects (SFX)

sounds, such as footsteps, ocean waves, or the squealing of automobile brakes, that are heard in a radio or television program or commercial in accompaniment to the script and that add to the mood or atmosphere of the presentation. Sound effects are produced by playing a recording of the actual sound that has been made previously wherever the sound actually occurred, or by recreating the sound by approximating the conditions under which it actually happens, or by using special devices and props to approximate the sound itself (such as crinkling cellophane to simulate the sound of fire).