Sound Effects techniques

from Wikipedia's 'Sound Effects' site:

'... As the car example demonstrates, the ability to make multiple simultaneous recordings of the same subject—through the use of several DAT or multitrack recorders—has made sound recording into a sophisticated craft, and allows the sound effect to be shaped by the sound editor or sound designer, not just for realism, but for emotional effect.

Once the sound effects are recorded or captured, they are usually loaded into a computer integrated with an audio non-linear editing system. This allows a sound editor or sound designer to heavily manipulate a sound to meet his needs.

The most common sound design tool is the use of layering to create a new, interesting sound out of two or three old, average sounds. For example, the sound of a bullet impact into a pig (from the above example) may be mixed with the sound of a melon being gouged to add to the "stickiness" or "gore" of the effect. If the effect is featured in a close-up, the designer may also add an "impact sweetener" from his library. The sweetener may simply be the sound of a hammer pounding hardwood, equalized so that only the low-end can be heard. The low end gives the three sounds together added weight, so that the audience actually "feels" the weight of the bullet hit the victim. If the victim is the bad guy, and his death is climactic, the sound designer may add reverb to the impact, in order to enhance the dramatic beat. And then, as the victim falls over in slow motion, the sound editor may add the sound of a broom whooshing by a microphone, pitch-shifted down and time-expanded to further emphasize the death. If the movie is a science-fiction film, the designer may phaser the whoosh to give it a more sci-fi feel. (For a list of many the sound effects processes available to a sound designer, see the bottom of this article.)