Chavin

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Chavín de Huántar Archaeological Acoustics Project

Acoustic Measurement, Archiving, Analysis, Modeling, and Simulation/Installation

Overview

Chavín de Huántar is a monumental World Heritage archaeological site [1] in the Peruvian highlands predating Inca society by over 2000 years. Since 1995 Professor John Rick of Stanford University and teams have been excavating the site [2], revealing peculiar and unique architectural features in both surface and underground structures. It is the underground structures, a complex of labyrinthine galleries and corridors, that are of particular interest to this project, because explanations for their purpose and function have led to Rick’s hypothesis that they were constructed, at enormous cost in labor, to establish social hierarchy through sensory manipulation in the context of religious ritual: a priest-elite over the novitiates.

In 2001 Rick discovered in one of the galleries twenty engraved ceremonial Strombus (conch) trumpets, some of which showed (through wear) use over several centuries. This important discovery reinforced his hypothesis that the acoustic properties of the underground part of the site were fundamental to the ancient ritual and perhaps even a determinant in architectural layout and design. One of the important (and enticing) questions is whether there is an acoustical relationship between the Strombus trumpets and the dimensions and layout of the underground galleries. That is, are the acoustic properties of the Strombus trumpets in any way coupled to the resonant frequencies and temporal features of the galleries and corridors? Finding an answer to this question will provide Rick with data to further elaborate and refine his hypothesis regarding the importance of sensory manipulation in Chavín ritual.

Since an important area of research at CCRMA is physical modeling of acoustic sources and reverberant spaces, we saw the opportunity to join two disciplines with the purpose of extending Rick’s three-dimensional measurements and CAD renderings of the site to include physical models of the site’s acoustics, with excitation sources such as Strombus trumpets, rushing water through canals both above and beneath galleries, and the human voice. Acoustic measurements and models of a site can be used to archive site acoustics, estimate the acoustics of inaccessible or alternative site architectures, and reconstruct original site acoustics; they may also be used to corroborate aspects of rituals suggested by other archaeological data. Measurement and modeling may be used to understand the implications of auditory experiences within these galleries as related to the role of the site in developing religious authority.

It is notable that because Chavín de Huántar presents intact enclosures primarily without post- period modification, acoustic measurements can be made throughout much of the site that closely reflect period conditions. Such an opportunity to archive relatively unmodified ancient architectural structures is rare. However, this opportunity may soon be altered: Chavín de Huántar is an important touristic attraction; thus the Peruvian government must make the underground galleries safe for visitors, adding reinforcing structures that will irreversibly alter the acoustics. It is therefore imperative that onsite measurements be made soon, precisely, and thoroughly.

The project is divided into three phases as shown below. Phase 3 represents the ultimate goal: a complete and site-independent virtual simulation over multiple loudspeakers, produced using a computer-based model of the acoustics of the underground galleries and above-ground plazas. These acoustic models will provide a rich research base with which to evaluate a variety of acoustic conditions, architectural geometries, source placements and listening positions within the galleries. Such a simulation can also be exhibited as an installation/virtual walkthrough, at both the Chavín museum in Peru, and at Stanford, reconstructing an auditory-visual experience of the original galleries.


Team Information

Co-investigators:

  • John Rick, PhD, Professor, Stanford University, Archaeology/Anthropology
  • Julius O. Smith, PhD, Professor, Stanford University, Center for Computer Research in Music and Acoustics (CCRMA)/Electrical Engineering (by courtesy)
  • Jonathan S. Abel, PhD, Consulting Professor, Stanford University, CCRMA
  • Patty Huang, MA, Graduate Student, Stanford University, CCRMA
  • Miriam Kolar, MFA, Graduate Student, Stanford University, CCRMA

Coordinator:

  • John Chowning, DMA, Professor Emeritus, Stanford University, CCRMA/Music

Local Collaborators:

  • Christian Mesia, Ph.D, Instituto Nacional de Cultura, Lima

Team Background:

  • John Rick has been heading excavations and directing research at the Chavín site since 1995
  • Digital waveguide techniques were pioneered at CCRMA by Julius O. Smith III
  • Julius O. Smith and Jonathan S. Abel have been working together on acoustic array processing and related problems since 1985
  • Patty Huang is a PhD student working under Abel on physical modeling and analysis of reverberant spaces
  • Miriam Kolar is a PhD student with extensive field experience in recording engineering
  • John Chowning is a composer having long standing interest in spatial modeling
  • CCRMA has expertise in field measurements, psychoacoustics, digital signal processing, and artificial reverberation

Phase 1. Preparation and Onsite Measurements

Preparation

  • Preliminary on-site tests [completed 12/07]
  • Preliminary on-site tests [to be completed 3/08]
  • Specification of test and recording equipment [ongoing; 1-2/08]
  • Purchase and assemble gear [ongoing; 2-?/08]

Simulation Trials in local environments

  • CCRMA stairwell, hallways, “Pit”
  • SU subsurface spaces-“famous” steam tunnels
  • Outdoor space similar to Chavín Circular Plaza?

Specify Provisional Mapping (for sound source-receiver placements from CAD rendering) [in progress; 1-?/08]

  • from each chamber to main space
  • least damaged areas
  • with and without plastering
  • peculiar geometries (e.g. , adjoining (comb-like) chambers, etc.)

Onsite Measurements at Chavín

  • Plastering of section of Chavín (selection of plastered sections is critical (soon after arrival to allow for drying)
  • Adjust mapping of source-receiver points

Measurements -- Sources

  • balloon pops
  • speaker-generated sinusoidal chirps
  • other signals
  • strombus trumpet live/recorded
  • record stream/water sound, wind noise

Measurements -- Receivers

  • distributed mics
  • in-ear-canal mics

Costs

  • $3,000 (2/08) equipment
  • $13,000 (summer 2008) equipment, data collection costs, logistical support [estimated; final costs TBD]
  • $8,000 travel and accommodations (2 weeks on site) for 2 faculty (Rick, Abel), 2 graduate students (Huang, Kolar)
  • $1,000 on site wall-building, plastering, and removal (summer 2008)

Potential Sources of Funding

  • Stanford Institute for Creativity in the Arts (SICA) [3]
  • National Geographic [4]

Equipment Loan

  • Sennheiser Research Lab

Acoustics'08 Paper [5]

  • Presentation in Paris, June-July 2008

Phase 2. Analysis and Generation of Physical Model

Analysis

  • compare plastered and unplastered and extrapolate to the entire structure
  • IR measurement to render the modeled spaces
  • measurement processing to model the pristine state
  • Strombus trumpet

Physical Model

  • calculate acoustical properties of materials
  • rendering from architectural models
  • use waveguide mesh processing
  • Stanford invention of and current work with waveguide mesh allows effective method to address computation/simulation of acoustical spaces
  • process and match/fit measurements then extend to parts of site that aren't necessarily intact or accessible for comprehensive measurements (plastering).

Potential Funding Sources

  • National Geographic [6]
  • National Endowment for the Humanities- Collaborative Research Grants [7]
  • National Science Foundation- Archaeology and Archaeometry [8]

Phase 3. Electroacoustic Simulation & Public Interface

Locations

  • Stanford
  • Chavín Museum
  • National Museum, Peru

Public Interfaces

  • Virtual walkthrough (headphone tour) in present condition
  • Virtual walkthrough (headphone tour) in reconstructed condition
  • Enhanced reverberation system for visitor experience
  • Installations of replica in various formats (online, DVD, museum, show, etc.)

Conservation & Reconstruction

  • Quantify and compensate for support structures
  • Simulation of plastered walls
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