When we watch movies, we tend to focus on the general storyline and characters but we take certain things for granted that also make the movie realistic. Sound effects don't actually come from the actors themselves, there is usually someone behind the scenes who creates realistic sound effects to match the movie. They are called foley artists and they recreate everyday sounds to enhance the audio quality which most audience members don't even notice because they are so well timed and integrated into the film in post-production.
It makes the movie appear more realistic and be so detailed as to just creating soft background noise. It can also serve to cover up background noise such as cars passing by or an aeroplane flying overhead. Foley artists have all sorts of tricks for simple sounds, like using a feather dister to create the sound of bird's wings flapping or cellophane for a crackling fire.
When you actually see the props they use to create simple sounds, it seems like such an arbitrary thing to experience. Next time you watch a movie, try to think about what they would use to create that sound!
Check out the video below and be amazed!