Fold Interference Sonification

The motivation for this sonification is to represent geological fold interference patterns through sound to celebrate the seminal work of structural geologist John Ramsay and present a new way to view’ geological structures and processes.

The contorted rocks of ancient Caledonian mountains at Loch Monar are a location where Ramsay meticulously mapped and subsequently unravelled multiple superimposed fold structures (see text by Rob Butler). These provide strong inspiration for this sonification.

Superposition of folds

The superposition of folds is essentially a set of different folding episodes being layered on top of each other. Re-folding events can produce an array of spectacular patterns. When a distinct time period, direction or strength of material is involved, the different episodes of folding can be unravelled. Ramsay established how individual elements interacted to give a richness of structure and pattern, describing 3 main fold interference patterns that depend on the relative orientations of fold interactions.

Sonification design

In their simplest form, geological folds strongly resemble sine waves. In this sonification, I combine and modulate basic sound waves using different sound synthesis techniques to represent the folds, their interaction and the rich patterns this interaction can produce.

FM synthesis folds sonification

During this sonification I take us below the surface of the earth to experience two sets of geological folds interacting. Frequency modulation and LFOs gives each fold set distinct rhythms and timbres. For a little more tangible experience for listeners, the first set of folds {B1} are also given their own rising theme which is subsequently deformed into a falling theme and additional elements when the second fold event {B2} has distorted’ with them. There are additional smaller sonic folds superimposed (as seen at Monar - see photograph above) that oscillate at higher frequencies or enjoy a bit more resonance. I add concrete ambience sounds and make use of panning and shifts in volume to give a sense of being surrounded by this moving dynamic world of folds.

what we hear

00:00 - {B1} is introduced > Initial LFO and FM modulation give a rhythm > several harmonics are playing are playing across octaves > the LFO is suppressed and cutoff reduced to suggest depth and ambience is bought forward > rising pitch {B1} theme introduced (00:20) > some inharmonics give an edge and reinforcement of the rhythm with sympathetic beats that follow the main pattern > 01:08

01:08 - {B1} theme is repeated > superimposed folds are heard a little brasher and harsher and more distinct > still underlain by the low octave {B1} > more rapid oscillations as {B2} approaches > 02:00

02:00 - {B2} additional variable beats are heard > (02:12) falling pitch suggests the modulation of {B1} folds by {B2} event > additional offset pitches of this same timbre are further evidence of the deformation of this original {B1} theme by {B2} > falling scales not quite reaching original B1 pitches > 03:10

03:10 - elements of {B2} and {B1} are superimposed > detuning harmonics and chorus effects split into two oscillators > one of the pair almost resolves to the original {B1} pitch > pulses where the original warmer deeper {B1} and the brighter timbre of {B2} is heard slightly higher pitch and slightly delayed > 04:04

04:04 - The two distinct folds are clearly heard with {B1} always forming a base line underlying the slightly higher pitch and higher gain of {B2}. We leave the scene with the two fold sets distinct but coexisting in our minds > 04:44