Show Dates:

Water : Image 4th – 6th July 2012 Conference to celebrate the 10th year of summer symposia organised by Land/Water and the Visual Arts Plymouth University, UK


Related publications:

Palmer, M (2011) "On breathing and geography – sonifying the Severn as shared generative art practice", ISEA conference, Istanbul, September 2011

Jones, O (2010) "Another Place": affective time-spaces of tidal processes as rendered in literature and art, in T. Edensor (ed) Geographies of Rhythm, Oxford: Ashgate, pp 189-203.



Michaela Palmer at

Sonification process

Sonic Severn site

Musings on how best to sonify or record self-dispensing and flocculating muds.
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Sound samples

listening to sounds

Sonic models of some of the mud behaviour.
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Indeed, there is nothing quite like it, and in the Severn Estuary there is also plenty of it.
But why sonify it?
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Fantastic Facts

What mud consists of, and why it is important to know how it behaves in the Estuary.
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Sedimentsonority is an art project that aims to model some of the sediment movements in the Severn Estuary, UK, using sound.

Translating the tidal mix of salt and freshwater, dispensed solids and biomatter into sound is truly fascinating, as here processes of self-organization become audible. Discovering and reflecting on this can reveal deeper philosophical issues, such as our often-limited understanding of water processes, or of how the world around us organizes itself. Exploring sediment characteristics via sound can lead to a deeper understanding of tidal landscapes and the complex processes they adhere to.

Sound is a medium we readily immerse ourselves in. Although the movements of estuary muds could be easily visualized (see map below), this process removes the viewer from the object it aims to explore. Indeed, not many art projects about water place the viewer/listener actually inside it. Yet the immersive viewpoint is valuable, as it allows us to re-experience a place with our senses.

Map showing the sediment leaving the Severn Estuary

Sediment leaving the Severn Estuary, copyright © 2008-2012 Chelys srl

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Fantastic Facts about Severn Estuary muds

mud and sandflats
  1. Places like the Severn estuary are the most productive ecosystems on the planet. For example, it is estimated that about 30,000 snails can be found within each m2 of mud. And the Severn Estuary contains about 100 km2 of intertidal mud flats!
  2. Another phenomenon are its quicksand pools, often concealed within sand banks, that make walking at low tide quite tricky.
  3. The funnel shape of the estuary amplifies the incoming tides, sometimes creating a surge wave, the Severn Bore, which if the conditions are right can travel upstream unbroken for many kilometres.
  4. During the incoming tide, much of the estuary mud re-suspends itself and forms large-scale mobile or static suspensions (slugs and pools), which then disappear again with the outgoing tides. This kind of dynamic self-organization has often been described in complexity theory, but in the estuary, it can be readily observed.
  5. Tidal pumping, the increased transport of sediment towards the head of an estuary, occurs during spring tides. Tidal pumping and the tendency for sediment to settle during neap tides causes so-called estuary turbidity maximia (ETMs), which make it very difficult to predict where exactly sediments may go into (re)suspension, and where they may settle.
  6. During spring tides, the accelerated flow of water means that a larger amount of silt is re-suspended and moved about in the estuary. Then about 30 million tonnes of fine sediment are in suspension.
  7. Severn estuary mud originates from small rivers, like the river Parrett. It is a mixture of clay minerals, sands and polysaccharides (mucus produced by mud-dwelling microorganisms). The sands and the polysaccharides render the mud more cohesive and increase its ability to bind pollutants (heavy metals, pesticides, etc) present in the water.
  8. Researchers have found that, despite their mobility, fine muddy sediments are being maintained in the estuary for 10 years or more. So only in certain tidal and weather conditions can toxic waste that is released into the water actually leave the estuary.
  9. Waves with fetches of up to 6000km extending into the Atlantic Ocean generate strong currents near the bed of the Severn estuary. These currents influence whether mud suspended in the estuary can settle or not: where the near bottom currents are strong, we find areas of exposed bedrock, where they are weaker we find gravel, sand or mud.
  10. Map of sediment distribution the Severn Estuary

    Materials at the bottom of the Severn Estuary.

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Sonification process

Sediment recording in a tank

Field-recording fine sediment movements is difficult, since the sounds are quasi-inaudible and easily overpowered by other environmental sounds. Using a hydrophone in shallow water, one might hear traffic sounds above water more readily than any sediment movements.

Recording sediment movements in a tank also has its draw-backs, as it is quite likely to record the sediment scraping against the container and not the grains or flocs brushing against each other.

Data sonification would be an alternative, however, data sets covering an area of sufficient space and time in the Severn Estuary are not readily available. Data from various studies would have to be pieced together, or new probes that allow for continuous measurements deployed.

This leaves sonic modelling. Since there are so many sediment phenomena (flocculation, forming of slugs, pools, funnel effect, tidal pumping, etc) it is useful to limit what is to be modelled, otherwise the listening experience can quickly become unclear.

Parameter mapping is a useful tool in the construction of such a model. For example, one could model different mud/water mixtures, using a programming environment such as Max/msp, stereo/ surround sound panning and granular sound synthesis:

Types of mud suspension: acoustically modelled with granular synthesis:
Mobile suspensions moving in the water with the tide. Similar viscosity to water. Small floc sizes. Depend on basination, tidal movements, and proximity to river mouths. Fast-moving, dense cloud of sound grains, moving rhythmically within a stereo or surround field.
Stationary suspensions are not moving horizontally with the tide, but gradually settle during slack water periods. Less dense cloud of sound grains, slowing. Lower pitched. Stationary.
  • Fluid muds have reached a ‘gelling point’ where the water between the mud particles has been expelled by gravity. More consistent in texture, but still mobile, and up to 5m thick (more in some places), making it difficult to navigate the estuary by boat.
  • Slow-moving grains, extended grain duration. Stationary.

    The sonic modelling of these three mud/water mixtures by themselves may not yet make for a truly captivating listening experience. But when this becomes a part of the sonic modelling of a larger-scale phenomenon, like a slug (a large-scale mobile mud suspension), they most likely will. The only question is how to map the parameters in more detail.


    One method of modelling a slug's movement within the estuary waters is by using 3D Boids.

    Boids were originally developed to simulate the flocking behaviour of larger objects such as birds or fish.

    However it should still be appropriate to use boids in this context if each boid represented not a single mud particle, but the centre point of a dispersed sub-swarm.

    The clip to the right shows Eric Singer's 3D Boid external for Max/msp in action.

    Using a 3D boid modelling program, it also becomes possible to link the spatial boid data to a surround sound field. This holds the key to creating an immersive listening experience.

    Thus using 3D boids to model the mobile mud suspension, further qualities can be sonically described. For example:

    Slug characteristic: Boid parameter:
    Dimension (width, height, diameter) maximum inter-boid distances
    Depth under surface centre point position on z-axis
    Location & movement in the estuary centre point position on x- and y-axes
    Lutinosity (depends on presence of mud, sand, organic materials) presence of different kinds of boids, exhibiting different behaviours, generating different sound timbres
    Densityincreasing / decreasing number of boids
    Expanding/ contracting slugincreasing/ decreasing attraction of boids to centre point and/or to each other
    Forming/ dispersing slug granular synthesis (as outlined in table above)

    Combining granular synthesis and boids in this manner provides a useful set of parameters for the modelling of self-forming and self-dispersing mud suspensions. The model not only allows for the computation of different environmental conditions, but can also be used to interpolate real data points. The emerging sounds can be easily translated into 3D audio file.

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    Sound samples

    The file starts out very quietly. For full effect, please use headphones. If you cannot see the audio player above, please click here

    A longer sonic model of three clouds of self-dispensing mud clouds (3:57 mins). First a local, very mobile suspension, then a stationary suspension that self-disperses, then a remote slug that approaches and settles.

    Examples of individual sediment/sound mappings:

    If you cannot see the audio player above, please click here

    A self-forming cloud of sine droplets. Representative of previously settled mud that is self-dispersing with an incoming tide.

    If you cannot see the audio player above, please click here

    A cloud of sine droplets moving right to left to center. The panning could be representative of how a mobile mud suspension moves along with a tidal wave.

    If you cannot see the audio player above, please click here

    A single sine droplet, pulsing and drooping from a set frequency. Each sine droplet is being modified with a randomised glissando. Several hundred of these droplets would be overlaid to represent a 'mud cloud'.

    If you cannot see the audio player above, please click here

    A cloud of (somewhat harsh sounding) mud grains is beginning to slow down its movements and sink.

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    More details and frequently asked questions

    What are spring tides?

    spring and neap tides

    When the moon is either full or new, the gravitational forces of moon and sun work together. Then the high tides are very high and the low tides very low, a phenomenon known as 'spring tides'. During the moon's quarter phases the gravitational forces of moon and sun work against each other. The result is a much smaller difference between high and low tides, a phenomenon known as 'neap tides'. More frequently asked questions

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    What is granulated sound?

    Sounds which underwent a process called granular synthesis. This is a method by which sounds are broken up into tiny grains, which are then pitch-shifted and/or time-stretched to form other sounds. A sound grain is a small piece of sonic data, about 10 - 50 ms in duration.

    If you cannot see the audio player above, please click here

    Example of some fairly unprocessed granulated sounds.

    What are boids?

    Boids was the name of an artificial life program, developed by Craig Reynolds in 1986, which simulated the flocking behaviour of birds. Each boid follows a set of parameters and generally moves towards an attractor point. The emergent behaviour depends on the interaction of the boids, and how the parameters are set. More frequently asked questions

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