Mapping the Acoustic Ecology of Chavin de Huantar

Chavín de Huántar (12.05°S, 76.98°W), a celebrated Peruvian archaeological site located in the Andean highlands, was the spiritual and administrative seat of the Chavín culture, which flourished from approximately 1200 BCE to 400 BCE. At the confluence of the Mosna and Wacheqsa rivers, the site contains remains of an impressive series of stone structures, underground passageways, and a sophisticated system of water diversion and runoff. Progress in the study ofFine Signal HomingStudies of residual sonic signatures, trapped in the site’s lithic and sediment matrices, have revealed to researchers the sophisticated acoustic ecology of the site’s builders.

The architectural configuration of the site includes a system of canals and galleries that have been designed to affect sound. More than a device for the discharge of water, the canals and galleries function as infrasonic resonators that affect the perception of sound. By using gravimetric resonance mapping and differential interferometry, it has been possible to begin to determine the spectral decay of acoustic events from past times, with the findings confirming that the architecture had modulated both environmental and ritual sounds in order to affect the social experience and perceptions of those individuals living in the site during the Andean Formative period.

At a glance

• Location:The region is Ancash, in Peru. The elevation is approximately 3,180 meters above sea level.
• Primary Period:1200 BCE – 200 BCE (Andean Formative).
• Key Structures:Old Temple (U-shape), New Temple (El Castillo), the Circular Plaza, and the Great Image (Lanz%f3n) Gallery.
• Technical Discovery:Identification of a 20-unit ensemble ofStrombus galeatus(shell trumpets) in the Gallery of the Offerings.
• Acoustic Range:Instrumental signals were observed to occur between 300 and 600 Hz. Structural infrasound occurred below 20 Hz.
• Methodology:Homning with Fine Signal, Acoustic microscopy and multi-channel microphone array recording.

Background

Most studies on Chav%edn de Hu%e1ntar focus on the stone iconography and the regional impact of this pre-Columbian settlement. Recently however, studies on the non-visual aspects of the site have been carried out within the frame of the new discipline of archaeoacoustics. Fine Signal Homing is a specialized research area within this field of study, which uses high-precision sensors to detect modulated ultrasonic and infrasonic echoes that are preserved in consolidated sediment as well as in fired ceramics. These Fine Signals travel through architectural spaces and materials and register the vibrational patterns that are imprinted in them, and which are related to the specific use that was made of a site or an object in the past.

The Andean Formative period was marked by the rise of the complex ceremonial centers of the region. These centers focused on the manipulation of the senses in order to produce social hierarchy. At Chav%edn, for example, the subterranean tunnels were built with precise masonry in order to contain sound in these space. Contemporary research is now calibrating the differential interferometry arrays in order to isolate the frequency of sound produced by tool use, voice, and percussion in these tunnels. That research will provide acoustic ecology data that can be analyzed through spectral analysis, rather than mere observation.

Hydraulic Engineering and Infrasonic Resonance

Of significant note are the extensive hydraulic systems that traverse the Chav%edn de Hu%e1ntar temple. Their function to manage high-altitude runoff from the surrounding mountains is complemented by their inherent ability to serve as acoustic generators. Fine Signal Homing analysis of the stone-lined tunnels indicates that, when water moves through them at specific velocities, they produce infrasonic resonance which would have been audible by temple-goers within the galleries even though the source of the sound is below ground.

Vibratory Signatures in Subterranean Canals

Using acoustic microscopy, researchers have investigated the interior surfaces of the tunnels of the drainage canals of the temple. The investigation has revealed a multitude of micro-fissures and wear marks on the surfaces of the tunnel system which can be correlated to specific frequency ranges. The resonance mapping of the water turbulence in the canal system shows that the temple tunnels function as waveguides, amplifying the low frequency part of the water movement. The temple thus produces a variety of infrasonic signatures, most of which are below human hearing but may be felt as vibrations. It is hypothesized that these sounds also have an effect on the psychology of visitors to the temple, and could explain the feelings of awe and even of disorientation that many people report when visiting the temple.

The "Roaring Temple" Hypothesis

Data extraction from the sedimentary matrixes of the Canal of the Labyrinths has shown correlation between hydrological events and harmonic overtones. During heavy rain the resonance in the building would have reached a peak. The fine Signal Homing techniques have been able to pick up the faint echoes that modulate within these sounds. It becomes apparent that the building was designed to synchronize its acoustic with the natural hydraulic acoustic output. This would allow for early environmental engineering in order to create a ritual field through synthesized natural sounds.

The 2001 Stanford University Acoustic Study

In 2001, a multidisciplinary team of researchers from Stanford University, led by archaeologist John Rick, and acoustician Miriam Kolar, conducted an in-depth analysis of the acoustics of the site. During this study, 20 different spaces were tested to see how they would sound.Strombus galeatusShell trumpets, known asPututus, found in The Gallery of the Offerings. These objects provide a physical connection to intended sound in the architectural space in which they were found.

Spectral Analysis of the Pututus

The 2001 study was set up with multi-channel microphone arrays to record the frequency response of shell trumpets played in the labyrinthine galleries. The results showed that thePututusThe fundamental frequency of the produced sound ranged from 300 to 600 Hz and therefore corresponded perfectly with the gallery’s resonances. The sound carrying shells – that were decorated with iconographic paintings similar to the site’s stone tenon heads – proved to be a very precise and above all a directional sound instrument.

Acoustic Modulation and Social Control

The galleries of Chav%edn functioned as acoustic filters in the study at Stanford, where it was shown how the sound of a shell trumpet could appear to be coming from different directions to a listener depending on their position in the space. The complex reflections and standing waves created ‘acoustic blurring’ which, in terms of performance, would have made it impossible for the audience to localize the performer. Fine Signal Homing analysis of the gallery walls has revealed residual signatures of the percussive signals from the various points within the space and these have been used to recreate the pathways that sounds took during a ceremony.

Fine Signal Homing and Artifactual Matrixes

The analysis of artifactual matrixes (i.e. fired ceramics and petrified organic matter) using Fine Signal Homing. Isolate faint vibratory remnants stored in the object’s structure through acoustic embedding. Such analysis can discriminate between vibratory residual of ritual performance and that of daily household activity.

Advanced noise-canceling techniques and subterranean acoustic spaces or enclosures are needed in order to increase signal-to-noise ratios required for the work at hand. Chav%edn site has set up these acoustic spaces within the deepest of galleries at the site in order to mitigate environmental interference found in surface environments today. The acoustic data gathered from the site has revealed that acoustic ecology at Chav%edn was not a fixed system and instead underwent changes as the architecture of the temple evolved and became more complex. Acoustic calibration in the newer sections of the temple in particular increased in complexity in relation to sections of the temple that predated them.

Social Behavior and Acoustic Ecology

The incorporation of sound within the architecture of Chav%edn de Hu%e1ntar serves the purpose of social behavior modification. The building functions as a highly sensory environment. It is a very dark space and sound within the space is heightened, changed, or even distorted. The overall effect upon visitors is likely to have had a powerful impact and will have served to reinforce the position of religious leaders within the site.

"Chav%edn’s acoustic environment was a primary concern of the buildings’ designers, and it is easily as impressive as the architecture of the galleries. A series of enclosed spaces which form at once a stage and an instrument, in the galleries human and natural sounds are utilized as a means of social influence.

By using Fine Signal Homing, researchers have been able to identify typical spectral decay rates for acoustic signals in the transition between sunlit squares and dark galleries. The change in resonance in this transition from the Circular Plaza to the Lanz%f3n Gallery must have been felt as a sudden change by the participants in the ritual, isolates them from the outside world and leads their attention to the internal narrative of the ritual.

Technological Requirements for Data Extraction

There is a need for specialized equipment that can function in the damp underground environment at Chav%edn to ensure accurate extraction of data. The researchers have deployed differential interferometry arrays (DIAs) of laser tiles. The DIAs measure and record the minute vibrations in the gallery walls. The data from the laser tiles are then converted into digital signals that can be subjected to spectral analysis. Since the lithic material at Chav%edn is primarily of hard rocks of granite and sandstone, the acoustic remnants from these stones have good preservation compared to those from less dense materials.

The findings from these experiments can be interpreted through a phenomenological analysis of the data. The extracted data can be used to create a number of digital models that recreate the original acoustic environment of the Chav%edn site. This would involve taking into account the loss of organic materials such as tapestries and food offerings, which would have acted as sound absorbers. The use of Fine Signal Homing allows for a high-fidelity model of the acoustic ecology of the site to be recreated. This can allow for an interpretation of how the Chav%edn culture interacted with their built environment and with the natural environment around them.