HOW THE PERCEPTION OF A SOUND EFFECTS AT A BASIC HUMAN LEVEL
Anyone seeing the film Dunkirk at an IMAX theatre will agree. It is not just the visual aspect of the film but it is in great part, the audio that assaults the senses.
For the score Hans Zimmer has used an audio illusion to great effect which causes the tension build and build, like a corkscrew without end.
The rising tension is driven by the audio illusion that has appeared on a number of albums. The first time I came across it was on the play out of the album ‘Love Bites’ by the Buzzcocks. The effect also appears in ‘I am the Walrus’. It’s an effect will appear on a BFG track currently being recorded for “Pulling Wings From Butterflies.’
This effect is know as the ‘Shepard Tone’.
THE SHEPARD TONE
A Shepard tone, named after Roger Shepard (born 1929), is a sound consisting of a superposition of sine waves separated by octaves. When played with the bass pitch of the tone moving upward or downward, it is referred to as the Shepard scale. This creates the auditory illusion of a tone that continually ascends or descends in pitch, yet which ultimately seems to get no higher or lower.
You can hear the disconcerting illusion here.