Sonification Metaphors for Hydrological Data

RiverAndRain.jpgThe brief for River And Rain was to design a sonification soundtrack for a visualisation of the effect of rainfall on the concentrations of chemicals along the Hawkesbury river system over the period of a year.

Three sonifications of the rainfall data illustrate symbolic, iconic and indexical design Schemas for the same data set.

An animated visualization of the data showed the chemicals in the river as coloured bands, while a pointer stepped along a bar-chart of the daily rainfall record. It was difficult to switch attention between the river and the rainfall when watching the animation, and to remember the important events. The sonification was designed so that visual attention could remain on the river whilst listening. This made the effects of rainfall  on the river system easier to understand, and with a few repetitions the pattern of rainfall events became quite memorable.

Sonifications of 365 days of rainfall in Sydney from March 2008 to Feb 2009.

The sonification is designed to allow answers to the question “how much rain?” at any given time with four levels of ordinal response {none,  sprinkling, showers, downpour}.

The first version of the sonification provides these answers with {silence = none} and  three steps in the pitch and brightness of a Cello note for sprinkling, showers and downpour.

Although the sounds provide useful information, some listeners commented that  “the rain should sound like rain”. This is an important point and identified the need to consider the semiotics of choice of sounds in the design process. Although the sonification is organised to answer questions in the most direct way perceptually, the Cello timbre is arbitrary and provides no context or linkage to the concept of rainfall.

This next sonification was designed to have a “rainfall” metaphor that may provide more context for interpreting the meaning. An iconic sequence of rainfall-like sounds was created using the Sonification Sandbox which is a tool that maps spreadsheet columns of data into General MIDI channels. Since there is no rainfall in the General MIDI palette the noise-like Applause  channel was chosen as an iconically similar sound. The pitch mapping is inverted so that light rain sounds high and soft, and heavy rain sounds low and loud.

Designing a rainfall metaphor with the Sonification Sandbox
Designing a rainfall metaphor with the Sonification Sandbox

In this third version the data modulates the loudness of a recording of rain that includes thunder and wind and other context that adds to the indexicality of the sonification.  Nevertheless the rapidity of events is still distinclty artificial, and there has been a tradeoff in that zero rainfall is heard as a low level that could be interpreted that rain is falling all year round. This sonification was made with a combination of Excel to manipulate the data, and Csound to render it.

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