Foley sound is used to add sound effects to a scene. Either the sound was not picked up good enough on location or was not picked up at all. You can add sound from a library but that might not sound as authentic as you need. Not all sound effects found in the library are the exact sound you look for or last the desired duration.
If that is the case then you can record sounds in sync with the actions on the screen. You can run the video on a large movie screen of a TV on a loop or playing straight through the scene.
The above video is almost 20
minutes long and well worth the watch. It is one of the most comprehensive, and
entertaining overview of what a Foley artist does and what a sound studio looks
like. Hot Nerd Girl is not the best interviewer one could hope for, but Universal
Studios Foley artist Dean Minnerly makes the interview work and has some good insight
about Foley sound. You can skip from about 5:43 to about 14:16 for the more
interesting Q&A of the video. Not only does he show some sound recreation, but
also has a truly in-depth knowledge of the industry. Most other videos are just
people making sound effects.
In the below video you can see the application
of Foley artistry. Gary Hecker is the star in this more entertaining video he
shows you why Foley is an art. He doesn’t just rattle a horse bridle randomly,
he does it in conjunction with what he sees on screen. Camera perspective is
all too important when recording sound effects; as the horse gets farther,
rattle quieter.
When doing Foley you really have to
be aware what is happening on screen, what might happen next, and use your
imagination. The more creative you are to get an authentic sounding track, the
more you can trick the audience into believing it is authentic and belongs in
the scene therefore drawing them into the story subconsciously.