Kolar et al. Herit Sci (2018) 6:39 https://doi.org/10.1186/s40494-018-0203-4 RESEARCH ARTICLE Open Access The Huánuco Pampa acoustical feld survey: an efcient, comparative archaeoacoustical method for studying sonic communication dynamics Miriam A. Kolar1* , R. Alan Covey2 and José Luis Cruzado Coronel3 Abstract The 2015 acoustical feld survey on and around the central plaza platform (“ushnu”) at the Inca administrative com- plex of Huánuco Pampa advances understanding of Inca communication dynamics and innovates archaeoacoustical methodologies. We detail here a new archaeoacoustics method that cross-compares a sequence of human-per- formed sound sources along with a standard electronic acoustical test signal across survey points. This efcient and rigorous archaeological experiment produced extensible data and observations regarding Inca-designed site sonics and multi-directional communication dynamics. Our experiment design combines ecologically valid acoustical meas- urements with subjective researcher-observer data to chart sound transmission and reception of diferent classes of sound-producers, enabling the identifcation of environmental contingencies, and the estimation of site acoustical features. Calibrated, multiply repeated sonic test signals were measured from a strategically chosen set of geo-located and photo-documented source and receiver locations in absolute, relative, and subjective terms, simultaneously for each source-receiver pair. This method ofers a systematic and comprehensive understanding of site-specifc sonic dynamics via in-feld observations and data recording, frequency-range comparison across test signals, attention to acoustical metrics and psychoacoustical precedents, and emphasis on practical repeatability for a range of archaeo- logically relevant sound sources. Our study posits the central platform at Huánuco Pampa as a strategic point for Inca elites to both observe and infuence activities across the site, a fnding extensible to other such platforms. The promi- nent architectural platform would serve as a tool for multi-directional communication, as well as to facilitate messag- ing about elite presence and imperial identity through the projection of sonic-visual displays. Beyond producing data about Huánuco Pampa and Inca architecture, our case-study implementation of this new method demonstrates an efcient and systematic approach to tracing the acoustical contingencies of architectural materials in archaeological contexts. Keywords: Huánuco Pampa, Inca soundscapes, Inca administration, Inca platforms, Inca communication, Archaeoacoustics, Acoustical survey method, Archaeological soundscapes, Archaeoacoustical methodology, Pututu acoustics *Correspondence: [email protected] 1 Five Colleges, Inc, 97 Spring Street, Amherst, MA 01002, USA Full list of author information is available at the end of the article © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/ publi​cdoma​in/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Kolar et al. Herit Sci (2018) 6:39 Page 2 of 25 Introduction (psychoacoustics). Tis approach has rarely been applied Tis article details our case-study application of a new, to archaeological sites, where it can ofer valuable per- efcient, and comparative method for archaeological spectives on aural and embodied communication. acoustical surveying, a methodological contribution to archaeoacoustics and archaeological feldwork practice. Sonic communication was important to the Inca Empire, Inca administration, sonic communication, and acoustics and thus this site-specifc adaptation of theory and meth- of imperial space ods from acoustical science produces materially contin- Te Inca Empire (c. 1400–1530s CE) was the most pow- gent evidence for past human interactions. erful indigenous New World state, and one with dis- Te benefts of the new method described in this paper tinct characteristics from archaic Old World states. Te include attention to ecological validity and rigor through absence of writing in the pre-Columbian Andes imposed multiple forms of evaluation (measured, recorded, signifcant communication challenges for an empire that researcher-observed) using a sequence of archaeologi- ruled millions of people speaking diferent languages. cally appropriate sound sources whose difering acoustics Inca ofcials used the khipu, a knotted cord device, to enable a comparative analysis across sources with respect encode some classes of information, and they stationed to each survey location. In-situ testing of sonic commu- runners along their main roads to transmit messages nication dynamics can reveal features of site architecture quickly. Despite these aids, a ready means of disseminat- and its landform settings, as well as produce data for ing state-directed communications was lacking. reconstructive modeling. Experimental acoustical feld- Te constraints on Inca mass communication raise work enables ground-truthing of estimations from mod- questions about how a society might use sonic mes- eling techniques and anecdotal reporting. saging for state administration. Inca-style buildings Te case-study site for the application detailed in facilitated face-to-face communications, but the largest this article is Huánuco Pampa, an Inca administrative structures (called kallankas) accommodated no more center in the central Peruvian highlands, where we have than a few thousand people [3]. Inca-style architecture focused on acoustical communication dynamics aforded is not sufciently well-distributed to meet all imperial by its central plaza architecture. To evaluate historical communication needs, and large structures appear to descriptions of the sonic properties of Inca central plaza be restricted to royal estates, administrative centers, and platforms (as discussed in this “Introduction” section), we religious complexes [4]. Tese spaces facilitated encoun- draw on established acoustical science principles, meas- ters between Inca nobles and selected audiences, but urement, and analysis techniques. From a disciplinary they were less useful for broader or lower-order state perspective, archaeological interpretation typically deals communications. with lengthy time scales, whereas in contrast, archaeo- Many kallankas open onto plazas that could hold large acoustics research targets the shortest increments of time crowds, and Colonial writers describe the role of proces- that humans perceive, sonic events. Our study examines sions and plaza performances in Inca political and rit- physical dynamics of site spaces to reveal features of ual life [5, 6]. Te Haucaypata plaza at the Inca capital, immediate experiential valence. By tracing how humans Cuzco, was used for municipal and imperial ceremonies may have related to one another via spatial dynamics, we that gathered thousands of participants, while smaller can better understand patterns of spatial use over longer plazas in nearby palace compounds served complemen- timescales. Physics-based archaeoacoustics allows an tary functions [7]. In highland provinces, the Incas laid empirical examination of how architecture and environ- out huge central plazas at several regional capitals, the ment facilitate sound transmission and reception. Site best preserved of which approach 20 ha [8, 9]. Span- sonics are studied here as both temporally and spatially ish eyewitnesses to a festival at Hatun Xauxa described scalable, relevant to the understanding of site architec- a crowd of 120,000 that came “in squadrons” from sur- ture in its landform setting, and therefore the landscape rounding villages, gathering daily in the central plaza to archaeology. be counted and inspected by Inca ofcials [10]. Finnegan [1] defnes communication as “the intercon- Inca ofcials choreographed processions whereby necting of humans,” following from which Kolar [2] poses subject populations entered central plazas, designating that sound enables such interconnections, and by exten- spaces for diferent administrative and ethnic groups. sion, that sound-modifying structures and objects can be Having assembled a living provincial mappa mundi in a source of archaeological evidence. In our study, acous- the plaza, Inca governors moved among the assembly, tical science and auditory psychology guide our evalua- checking khipu records, assigning tributary responsi- tion of sonic communication dynamics, as a function bilities, and performing mass marriages to create tribu- of place (acoustics), and with respect to human sensing tary households [5]. After state administrative reviews Kolar et al. Herit Sci (2018) 6:39 Page 3 of 25 and ritual performances, provincial subjects dispersed from the Inca center, returning to local villages or set- ting forth on new service assignments. Colonial descriptions of Inca central plaza events emphasize the physical separation of the ruler and important supernatural objects (wak’a) from sub- ject populations. Platform spaces in the plaza allowed these powerful entities to be seen reviewing and bring- ing order to the proceedings. One detailed account of