Rhythm 

Rhythm is on of the most complex features of sound. Rhythm involves a beat or pulse a pace or tempo and a pattern of accents or stronger or weaker beats. 
 

• Music has rhythm

Rhythm is most recognizable in film music, since the beat, tempo, and accent are basic compositional features. 
 
• Speech has rhythm 

People can be identified by "voice prints" which show not only characteristic frequencies and amplitudes but also distinct patterns of pacing and syllabic stress. In fictional films, speech rhythm is a matter for the performer's control, but the sound editor can also manipulate it at the dubbing phase

• Sound effects have rhythm (e.g. rhythmic qualities) 

The plodding hooves of farmhorse differ from a cavalry company riding at full speed. The vibrating tone of a gong may offer a slowly decaying accent, while a sudden sneeze provides a brief  one. In a gangster film, a machine gun's fire crates a regular  rapid beat, while the sporadic reports of pistols may come at irregular intervals. 

• Images have rhythm

Any consideration of rhythmic uses of sound is complicated by the fact that movements in the images themselves have a rhythm as well, distinguished by the same principles of beat, speed, and accent. In addition, the editing has a rhythm. Short shots helps crate a rapid tempo, whereas shots held longer tend to slow down the rhythm. 

In most cases the rhythms of editing, of movement within the image, any of sound all cooperate. The most common tendency is for the filmmaker to match visual and sonic rhythms to each other. 
 

Fidelity 

By fidelity David Bordwell and Kristin Thompson do not mean quality of recording.  

Fidelity refers to the extent to which the sound is faithful to the source as we, the audience conceive it. If a film shows us a barking dog and we hear a barking noise, that sound is faithful to its source; the sound maintains fidelity. But if the picture of the barking dog is accompanied by the sound of a cat meowing, there enters a disparity between sound and image - a lack of fidelity. 

Fidelity has nothing to do with what originally made the sound in production.  A filmmaker may manipulate sound independently of image. Accompanying the image of a dog with the meow is no more difficult than accompanying the image with a bark. If the viewer takes the sound to be coming from its source in the diegetic world of film, then is faithful, regardless of its actual source in production. 

Fidelity is purely a matter of expectation. Even if our dog emits a bark on screen, perhaps in production the bark came from a different dog or was electronically synthesized. We do  not know what laser guns "really" sounds like, but we accept the wang they make in Star Wars. 

When we do became aware that sound is unfaithful to its source, that awareness is usually used for the comic effect. In Jacques Tati's Mr. Hulot's Holiday much humor arises from the opening and closing of a dining-room door. Instead of simply recording a real door, Tati inserts a twanging sound like a plucked cello string each time the door swings. Because many of the jokes in Mr. Hulot's Holiday and other Tati films are based on quirkily unfaithful noises, his films are good specimens for the study of sound 

Unfaithful sound may have dramatic functions as the accompanying sound to a kick or punch.  

More about dramatic functions of sound effects - Making sounds for Director Jonathan Demme