A film soundtrack can be analysed strictly in terms of the sound itself. This involves distinguishing between different types of sound (speech, noise, music) and describing their characteristics and interrelationships.
However, the status of sound in cinema is largely determined by its relation to the image. This means we can also distinguish sounds depending on where their source is located in space (in-sound, offscreen sound and off-sound), or on the point of audition (subjective sounds).
In cinema, sound is divided into three different categories depending on its nature : noise, speech and music.
Some descriptive criteria are common to all sounds : volume, pitch, timbre and rhythm. Others are specific to certain kinds of sound : for speech, there is accent, pronunciation, intonation; for music, instrumentation, composition and style.
The different types of sound are assigned different weights on the soundtrack. They can also echo each other.
The status of cinematic sound varies depending on where the sound source is located in relation to the image. Michel Chion developed a taxonomy that distinguishes between: in-screen, off-screen and "off" sounds, internal sounds (including inner voices), ambient sounds, and on-the-air sounds.
The acoustic treatment of sounds is determined by their status and the sound perspective.
A "subjective sound" is one that enables the viewers to adopt a character’s point-of-audition, as if they were hearing what he or she hears.
The subjective quality of a sound can be indicated by:
- Its association with the image of a character who is listening.
- An acoustic treatment that points to the spatial area of the point-of-audition.
- Distortions linked to the state of the character who is hearing.