Ambience

In filmmaking, ambience (also known as atmosphere, atmos, or background) consists of the sounds of a given location or space. It is the opposite of "silence." This term is often confused with presence. Every location has distinct and subtle sounds created by its environment. These sound sources can include wildlife, hearing the wind blow, music, rain, etc...

Ambience from Daniel Hughes on Vimeo.

Here is a short clip of how ambience can be portrayed within film and moving images. You can clearly notice how some of the sounds, such as the typing, have been amplified for a deeper effect, plainly for notice and relevant to a realistic atmosphere.
Ambience should be used in moments of dialogue with multiple characters talking. My interpretation is that it doesn't work for most scenes within a film, such as; narration, fight scenes, romantic endeavours, etc... Ambience sometimes just removes the mood from certain films and their particular aims & genres. It's only in moments of dialogue that it would truly work, and within certain locations like pubs, gyms, and suchlike. Other than all of the criticism, ambience works extremely well in public locations.
Within my version of a Film Noir's opening title sequence, I would like to include an ambience sound effect, but only in a scene which involves a publicly filmed location. Ambience is not an effect which I think would improve a film's standard by far, it's a timid effect. Small amounts would be fine.