Key Attributes of Sound and Music
There are a number of key attributes to sound and music that have an impact on the way that sound is perceived.
Volume or sound level
This can be adjusted while recording and again when dubbing. Any sound can be adjusted so that it is the loudest, most prominent part of the mix, or the quietest, so guiding audience judgement of the relative significance of each sound. (See Sound: introduction.)
Adjustments of sound level are frequently made audibly during scenes. However, as such adjustments are subservient to the story, we generally do not pay much attention to them, and the changes in level pass unnoticed. Increasing volume is called fading up, decreasing fading down, a fade up from silence is a fade in, a fade down to silence is a fade out.
A ‘high-pitched’ voice contains a relatively high proportion of high-frequency sound. A higher-pitched instrument, like a violin, is one that produces a range of notes that are mostly at a higher frequency than a lower-pitched instrument, like a double bass.
Pitch can greatly affect audience response: a low rumbling sound might imply menace, while a high, sustained note might create tension. The pitch of music is especially potent in affecting the meaning and reading of particular scenes: the famous shower scene in Hitchcock's Psycho, for example, is dominated by the even more famous high-pitched violins that accompany the awful murder. Most sounds contain a range, or spectrum, of frequencies, from lower to higher, which can be altered during dubbing by adjusting the equalisation, or EQ. The higher frequencies can be minimised or increased, for example, or the lower frequencies. This is similar to altering the treble or bass controls on an audio system, but with a larger range of adjustment.
Timbre refers to a sound's distinctive aural ‘signature’, which allows us to distinguish between, for example, a flute and a violin playing the same note. Individual sounds are a mix of many different frequencies present at different levels of volume, with the loudest frequency producing the sound's fundamental pitch. The other frequencies, called harmonics, are present in different quantities according to the sound source, and it is this mix of frequencies which gives the sound its ‘colour’. A flute produces a different mix of harmonics to a violin playing the same note; hence, the two instruments sound quite different.
The timbres of naturalistic FX are determined by their source in reality - a robin must sound like a robin, not a crow or a seagull, for example. However, timbre can also be affected by the location, real or implied, of a sound source. A robin singing outside a closed window will sound muffled: its timbre is altered because the high frequencies in its song are reduced. Suggesting location by altering sound quality in this way is an important aspect of sound mixing.
Many effects are less specific, more generic, and this is where post-production decisions become vital. A clock striking needs a bell effect, but what type of bell is appropriate?
The acoustic of a location refers to the amount and type of reverberation it possesses, and each room has a different sound signature. In a very large room, a sound will travel from its source - a voice, say - and take a comparatively long time to reach walls, ceiling etc. These surfaces then reflect the sound as ‘echoes’. Because the surfaces are at different distances from the source, the sound will take different amounts of time to reflect back, so one echo will be heard, then another, and another. This is reverberation. In the process of bouncing around the room, the reverberation finally fades to nothing, or ‘decays’ away.
A smaller room will have a different acoustic, as the echoes have less distance to travel, and therefore bounce around and exhaust themselves more quickly: the room will reverberate less. Furthermore, different materials reflect sound to different degrees: a sumptuous room of soft furnishings and velvet curtains won't reflect sound well, so the room will not reverberate. A cathedral has hard, reflective surfaces and vast spaces. Sound reflects well and bounces comparatively slowly from one surface to another, so a very characteristic ‘church acoustic’ results. A ‘dry’ acoustic has little reverberation, in contrast to a ‘wet’ acoustic.
Artificial reverberation can be added at the dubbing stage, when it is generally known as ‘reverb’. Reverb (or lack of it) can be used to help suggest the size of a space represented on screen. Reverb can also suggest off-screen space, such as footsteps retreating down a hall.
Large interior spaces, such as castle halls, caverns, cellars, basements, underground car parks, and, of course, staircases in big old houses are often threatening places in films. There is always the possibility that they may contain unseen dangers in their shadowy nooks and crannies. A reverberating acoustic can thus become powerfully suggestive of danger.
We can tell with our eyes shut whether a sound is near or far away and from which direction or angle it is coming. The closer it is, the louder it is. This ‘sound perspective’ provides us with important spatial clues about our environment. It is natural to link shot size with sound perspective, because the nearer we are to something, the louder it will be. Someone who is speaking in the distance (in an extreme long shot) won't usually sound as loud as in a close-up.
As with other conventions, this one may be broken for deliberate effect or for clarity. For example, in a film it is by no means unusual for people conversing in the middle-distance to be heard clearly, while those in the foreground are inaudible.
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Written by Scott Donaldson