When sound effects are realistic, they are taken for granted, thanks to Jack Foley, who invented the way that this is done.
A film audience is not meant to be consciously aware of the sounds — separate from the dialogue — that are audible most of the time, yet if these were missing from the sound track, it would indeed be noticeable and even disturbing. We expect to hear what we can see happening on the screen and have it be identifiable. To this very day, movies and television programs will list Foley artists in their credits: a continuing homage to the man originally responsible for coming up with the system for adding sound effects back into filmed footage. Jack Foley began his career during the era of silent film and was, it is fair to say, largely responsible for guiding hitherto soundless production over the threshold of “talkies”.
Key chains stand in for leg chains, and sound effects save the day
Because sounds resulting from onscreen activity could not be picked up reliably by the microphones recording the actors’ speech, this system came to be developed whereby the sound effects would be created on what is known as a Foley stage (an environment with various types of surfaces and countless props) in synchronization with the movement shown on the screen. The original master himself, Mr. Jack Foley, possessed skills and an imagination that have never been equaled. One legendary event involved his recreating an entire sequence in the movie Spartacus with the use of footsteps and keychains rather than having to send a huge cast back to a location in Italy after the fact to be filmed as slaves, shuffling along in leg chains.
Old-fashioned yet still relevant sound effects
This statement, taken from an interview, is a convincing answer (as is this clip) to the question of sound effects in our time and whether Foley artistry will continue to be necessary. Although there are substantial digital libraries available, they are perhaps only appropriate for less polished creations (or entirely digitized animations, which have possibilities to generate their own matching sounds in real time). For sound that truly matches the idiosyncratic movement displayed on the screen, it seems that the grace, rhythm, timing and other talents of Foley artists will always be in demand.