Listening to Weather Records: An Example of Sonification of Time Series Data
John H. Flowers, University of Nebraska--Lincoln
Sonification offers a novel means for displaying complex, multivariate, time series data, such as medical histories, climate records, and economic trends. Sonified displays can not only be useful to blind or visual impaired users, but they have potential for providing useful tools for data exploration by normally sighted individuals as well.
Features of weather records that lend themselves of sonification:
- Weather observations are a typical example of complex multivariate time series data that include both continuous numeric observations (temperature) and discrete “event” data (e.g. rain and snow episodes).
- Such records are sequential and thus map well to the sequential structure of an auditory stream.
- Weather events are familiar and are of interest to the general public, and thus provide a good forum for familiarizing the public with the potential utility of auditory displays.
- Weather records are very important for social and economic decision making, and scientific inquiry -- activities that depend upon developoment of effective display technology.
- Daily weather observations also constitute an important historical database for studying and teaching about climate change and regional climate differences (a currently "hot" issue for which effective data display techniques are crucial).
The data source for this project:
The climate records used for this project were monthly records of daily obervations of high and low temperature, rainfall, and snowfall from Lincoln, Nebraska, selected from the historical period of 1920 - present. These were obtained from the High Plains Regional Climate Center (HPRCC) at the Univeristy of Nebraska, Lincoln:
Sonification design issues: To make an effective auditory data display, one should...
- Map data variables to sound elements so that
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– Different variables are perceptually distinct.
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– Sound elements are meaningfully or metaphorically related to the data events they represent (when possible).
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Adjust the speed, duration, and complexity of the display to conform to limits of human attention and working memory.
Auditory mapping of Lincoln climate data:
- Temperature
- MIDI synthetic strings motif of four notes per day, alternating pitches that represent high and low temperature.
- Each daily high and low temperature is played twice for each day so that precipitation sound, so that at least one presentation would not occur simultaneously with precitipation data displays.
- Pitch scaled to a five octave range (C5 to C9) to cover the large yearly range of observed eastern Nebraska temperatures (-36C to +46C or -33F to +115F).
- Rainfall
Descending pitch sequence of one to three MIDI piano notes, for which the drop in pitch from the first to last note is scaled to rainfall amount.
- For less than 0.05 inches only a single sixteenth note (C9... the piano high C) is sounded.
- For 0.05 inches to 0.5 inches, a two sixteenth note sequence is prensented, for which pitch drop from C9 for the second note is scaled to amount.
- For amounts in excess of 0.5 inches, a three note sequence of played -- total pitch drop across the three notes is scaled to amount. An extremely heavy rainfall of 5.42 inches (the largests value encountered in data we have sonfied) is a five octave drop over three piano notes, C9, C7, C5.
- In addition, loudness the second and third notes is increased (MIDI velocities of 64, 80, and 96 across a three note sequence).
- Thus the number of notes, the amount of pitch drop in the note sequence, and the increasing loudness of the rain notes provide redundant cues about rain amounts on a given day. Metaphor: "Heavy rain comes down hard."
- Snowfall
- Ascending pitch series of one to four MIDI dulcimer sixteenth notes.
- Less than 1 inch, a single note.
- 1-2.99 inches, two notes.
- 3-5.99 inches, three notes.
6 inches or more (when school is almost certainly called off, plus other inconvieniences), four notes.
Metaphor: "Snow piles up."
Examples from warm season months:
Listen to July, 1936-- a very different, extremely hot and dry, dust bowl month.
Examples from winter months:
A musical score from parts of December, 2000 -- A gloomy, cold, snowy example:
Note that colder temperatures put most of the low temperatures in the bass clef. For reference, freezing (32F) is D above middle C. No liquid rain fell during the month.
Listen to February, 1999 -- a much milder month that contains light rain events as well as snow, and ends with a hint of Spring:
Ongoing research using these types of displays shows that
- Listeners can accurately perceive key meteorological features when comparing auditory displays from different months.
- Listeners are particularly sensitive to the temporal distribution of precipitation event across a month (more than with visual charts or numeric tables).
References
Flowers, J. H., Whitwer, L. E., Grafel, D. C., & Kotan, C. A. (2001). Sonification of daily weather records: Issues of perception, attention and memory in design choices . Proceedings of the 2001 International Conference on Auditory Display, 222-226.
Flowers, J. H. & Grafel, D. C. (2002). Perception of sonified daily weather records. Proceedings of the Human Factors and Ergonomic Society 46 th Anuual Meeting, 2002, 1579-1583.
