Chaco Canyon was the center of ancestral Puebloan civilization. It’s famous for its great houses – large, multistoried structures, some the size of football fields – built and used from approximately A.D. 850-1150. Archaeologists have studied how the Ancestral Puebloans built the structures of Chaco Canyon and placed them in relation to each other and to astronomical alignments.
To add a new dimension to our understanding of this time and place, we investigated how sounds were experienced at these sites. We wanted to know how a listener would have experienced a sound from a specific distance away from whatever was producing it.
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The software package we used, ESRI’s ArcGIS, offers anyone the option to create customized tools, such as the Soundshed Analysis Tool we created, to do calculations or create geographical data and images. The Soundshed Analysis Tool is derived from an earlier modeling script“SPreAD-GIS” developed by environmental scientist Sarah Reed to measure the impact of noise on natural environments, such as national forests. That tool was itself adapted from SPreAD, or “the System for the Prediction of Acoustic Detectability,” a method the U.S. Forest Service devised in 1980 to predict the impact of noise on outdoor recreation.
The Soundshed Analysis Tool requires seven input variables, a study location and elevation data. Variables include the sound source height, frequency of the sound source, sound pressure level of the source, the measurement distance from the source, air temperature, relative humidity and the ambient sound pressure level of the study location. We gathered this information from a variety of sources: open-source elevation data, archaeological research, paleoclimatological research and historical climate data. We also gathered from the relevant literature the decibel levels of crowds, individuals and the conch trumpet instrument ancestral Puebloans used.
Once the input variables are entered, it takes the Soundshed tool less than 10 minutes to crunch through this complex math for every point on the landscape within two miles of the spot where the sound is produced. Our model then creates images that show where and how sound spreads across the landscape. This gives us a way to visualize the sounds people would have experienced as they moved through the landscape, going about their day. (Source: The Conversation)
During the past few decades, researchers have developed methodologies for understanding how past people experienced their wider world. The majority of these reconstructions focused upon viewsheds and movement, illustrating how individuals visually observed their environment and navigated through it. However, these reconstructions have tended to ignore another sense which played a major role in how people experienced the wider, physical world: that of sound. While the topic of sound has been discussed within phenomenology at the theoretical level, and has been approached at the site level through the growing study of “acoustic archaeology,” there has been limited practical application at the landscape level. This article illustrates how GIS technology can be utilized to model soundscapes, exploring how people heard their wider surroundings.
