Types of sound effects.
When it comes to professional sound design and editing, audio and sounds are grouped into four major categories.
1. Isolated sounds are normal, everyday noises that you hear in daily life. Car beeps, barking dogs and jackhammers in a busy city are all isolated sounds. Isolated sound effects are usually easy to find in sound effect libraries and if you want something basic, like the sound of a door closing, royalty-free collections of audio clips will almost certainly have what you’re looking for.
2. Speciality effects are new sounds created especially for a production. Speciality effects are especially popular for fantasy and sci-fi. A dragon’s roar or the low hum of a lightsaber are not sounds that exist in the real world, so they have to be created.
3. Foley sounds, like speciality effects, are created specifically for a production. Often, Foley artists will time their sounds to whatever is happening on screen. If a character is walking through gravel, a Foley artist will record themselves doing the same, timing their steps with the character on screen. Foley effects are named after Jack Foley, an early sound effects designer who worked during the first years of sound filmmaking.
4. Ambience is the background sound of a given environment. The background noise of a city street is different from the background noise of a forest, which is different from the background noise of an office building. Every scene requires background ambience, otherwise it risks sounding unnatural.
Sources for sound effects.
There are two major ways to get sound effects for a production: Create them or license them. Most larger productions will create sound effects in-house, employing a Foley artist to create customised effects that match the needs of their media.
Smaller productions, though, usually rely on existing resources. Many original sound effects are archived in a sound effects library or bundled into a sound effects pack sold for commercial use. If you don’t have the budget for original sound, plenty of websites offer free, high-quality sound effects under a Creative Commons licence, along with other resources like royalty-free music.