PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Acoustic effects at prehistoric landscapes: an archaeoacoustics
analysis of rock art sites from the Western Mediterranean
Margarita DÍAZ-ANDREU1; Angelo FARINA2; Enrico ARMELLONI3; Laura COLTOFEAN4;
Mathieu PICAS5; Tommaso MATTIOLI61ICREA and University of Barcelona, Spain
2

University of Parma, Italy
3

4,5,6

AIDA S.R.L., Italy

University of Barcelona, Spain

ABSTRACT
Many pre-state societies around the world give special importance to places where distinctive
acoustic effects are generated. These places often receive special treatment including the productionof rock paintings in them. In the Western Mediterranean, it seems that outstanding acoustic effects
such as directional echoes, augmented audibility and long reverberation time are present in some rockart areas with Neolithic depictions made between the 7 th and 4 th millennia BC. These have been painted
in different styles that have been given the name of Macroschematic, Levantine and Schematic rockart styles. On the basis of the results of our acoustic tests, we argue that there is a strong probabilityof acoustics having been used as a method by Neolithic artists to select the shelters in which to produce
rock art. This paper presents the results of the ongoing ARTSOUNDSCAPES ERC Project onarchaeoacoustics. This project seeks to explore the role of sound in the creation and use of rock art
sites. he authors discuss the results of previous fieldwork in three countries (Spain, France and Italy)
and the development of an innovative set of research methods that include 3D Ambisonic recordings,
GIS soundshed analysis, and Transmission Loss measurements.
Keywords: Archaeoacoustics, Rock Art, Neolithic, Soundscape, Mediterranean

1. INTRODUCTION
In the last two decades archaeology has gone through a renewal in the analysis of the materials left
behind by past communities. Archaeologists are looking beyond the materiality of the past and trying
to recover other less evident and intangible cultural signs such as those related to the senses, including
hearing. These studies are based on the hypothesis that sound may have been as important for thepeople of the past as other more tangible aspects traditionally considered by archaeologists. Ourinterdisciplinary group formed by members of the Universities of Barcelona (prehistoric archaeology)
and Parma (acoustical engineering) have been collaborating since 2015 in order to test thesoundscapes of rock art landscapes. The first such collaboration took place in the context of the Marie
Curie SONART project and, since October 2018, it continues in the framework of the ERC
1m.diaz-andreu@ub.edu
farina@unipr.it
3
armelloni@aidasrl.it
4
laura.coltofean@ub.edu
5mathieu.picas@hotmail.fr
6
tmattioli@ub.edu
2281

ARTSOUNDSCAPES project.

2. ECHOLOCATION AND THE PLACEMENT OF ROCK ART
Several studies in psychoacoustics
have demonstrated that some people
have the capacity to locate places andorientate themselves by identifying
the exact location where echoes andsound reflections come from. Thisability, usually observed among blind
people - but also sighted people thathave been trained- is called
echolocation (2) (3: tables 1 and 2, 4).
Was echolocation used in the past? In
answering this question, one of the
major difficulties that archaeologists
are confronted with is that thisactivity does not need or leave any
sort of material culture.
In the field of rock art, theabsence of material evidence related
to echolocation has led specialists to Figure 1 - Shelters 30 to 34 on the eastern side of Baume Brune
search for indirect proofs connecting
echoes and rock art. A high (France). Only Shelter 3, the best sound reflecting surfaces of thecorrelation between rock art sites andcliff, has rock art (arboriform) (photo by the authors)places where echoes are produced has
beenmentionedby
severalarchaeologists (5). In most cases this correlation is made subjectively, based on the appreciations of
the auditory experiences that the researchers themselves have encountered at the sites (6-9). A moreobjective approach has recently been introduced by archaeologists Margarita Díaz-Andreu and Carlos
Garcia Benito in Spain (10, 11) and by Riitta Rainio in Finland (12). Both teams have conducted theirtests using procedures developed in the field of acoustical physics. It is in this line that the authors of
this article, an interdisciplinary team of archaeologists and acoustic engineers, have been working forthe last two years.
In 2015 our team developed a method to investigate the Direction of Arrival (DOA) of echoes andsound reflections. This method is a combination of 1 st Order Ambisonics recording technique andSpherical camera pictures, and it is adapted to fieldwork in open-air landscapes (13). We havedeveloped a specific software (called IR-Spatial) to post-process the 3D Impulse Response (IR) andto calculate the values for the azimuth, elevation and sound intensity of the sound reflections reaching
the listener. The software also creates a slow-motion video that enables us to “see” where the echoes
and reverberations come from during fieldwork. With the resulting data we calculated thecorrespondence between the DOA of sound reflections and the positioning of rock art shelters in thelandscape. This methodology allowed us to further approach the question of whether echolocation
was used by prehistoric populations in the selection and use of rock art sites. This methodology has
been applied in the Schematic rock art landscapes of Baume Brune (Vaucluse, France) and Valled’Ividoro (Puglia, Italy) (fig. 1). In both these areas, of the many available rock shelters, our results
indicate that only a few were chosen by artists at the end of the Neolithic, and that these shelters
corresponded with those with the best sound reflecting surfaces of each region.

3. BEING HEARD AT DISTANCE: THE PROPAGATION OF SOUNDS FROMROCK ART SITES
Ethnography and historical sources indicate that some rock art sites, especially those used asvenues for different activities, such as ceremonies with dance, music and sounds, were expected to be
audible at distance (14-17). In these places, the sound coming from rock art sites was used to informthe members of the community that the ritual in the decorated site had begun or finished. Blesser and282

Salter use the term “acoustic arena” to refer to the area where listeners become part of an acoustic
community, as they can hear the same sonic event (18:22). In the same way as everyone in a concert
hall wants to listen to the same music, or everyone within earshot of a church bell may feel rooted
within the same community, the people in the area around rock art sites might have been interested inhearing what was going on inside the decorated sites.
The concept of “acoustic arena” has important consequences: not only does it determine themaximum distance between a listener in the landscape and the source in the rock shelter, but it also
defines the size of the rock art audience. The size of the acoustic arena can vary depending on the
loudness of the signal and theability of the place to propagate
sound. The smaller the acoustic
arena, the lesser and more private
the audience. In this case great
importance might be given to thenegotiation about who should
legitimately participate in thisacoustic community. On thecontrary, the broader the acoustic
arena, the larger the audience. Thisimplies a broader message for large
gatherings of people.
In our project we haveinvestigated the propagation ofsounds from rock art sites bymodelling the so-called soundshedusing SpreadGIS for ArcGis (1). In
particular, we modelled the
propagation of sound from a set of
128 rock art sites in themountainous region of Alicante in
Spain. This area is unique in the
Figure 2 - Interval plot (central tendency and variability of theMediterranean in that it contains
data) of the audibility of sound produced within rock art sites in three different post-Palaeolithic
rock art styles, all of which cohectares according to the type of art: Macroschematic (M),existed during the Neolithic period
Macroschematic and Schematic (MS), Levantine (L), Levantine (c. 5600-2800 cal BC) (19): theearliest Macroschematic motifs,
and Schematic (LS), and Schematic rock art styles (S). (from (1)) and the somewhat later Schematicand Levantine styles. The chronological development and partial overlap of rock art traditions in thisarea allowed us to make comparisons between rock art styles in the search for patterns.
The data obtained from the soundshed analysis reveal interesting results (Fig. 2). Firstly, there isa clear difference in the propagation of sounds between Macroschematic rock art sites, on the one
hand, and Schematic sites, on the other, with values ranging from 12-33 hectares (Macroschematic)
to 33-44 hectares (Schematic). These results seem to indicate that when the first Neolithic artists, i.e.
those painting Macroschematic motifs, decided to decorate the landscape, they were less interested inreaching large audiences than the later Schematic artists. Instead, the creators of the latter rock art
tradition appear to have taken a great interest in audibility in the wider landscape. Secondly, a close
inspection of sites with two or more styles leads to further insights. When the Schematic artists had
to make decisions on where to paint, among all the previously painted Macroschematic sites theytended to choose only those that had higher audibility, thus revealing that acoustic perception was oneof the major elements in the selection of sites to be decorated. The results appear to reflect the relative
irrelevance of audibility for Levantine artists in the Mountains of Alicante.

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4. HEARING DISTANT SOUNDS IN ROCK ART SITES
The ability of rock art sites to propagate sounds
towards their surroundings has its counterpart in theirability to receive sounds coming from visually remoteplaces. In this regard, it is not unusual to find anecdotal
information in the literature about rock art sites atwhich sounds from the surrounding landscape can beremarkably well heard (20:123) (21:26) (22:10)(14:273) (10:3596). From an acoustical point of view,
the audibility of sound sources placed at far distancefrom the listener depends mainly on the topography ofplaces. Rocky landscapes full of hard vertical surfaces,
as is the case of most of rock art landscapes, often havethe potential to greatly enhance the auditory perceptionof distant sound sources. Canyon walls and vertical
cliffs act like a set of curved or angled mirrors thatbounce sound waves out and back at an unexpecteddistance, in a similar way to building façades in socalled “city canyons” (23). Interestingly, the use of themirror as a metaphor to explain the propagation ofsound beyond visual barriers was first mentioned byGreek and Latin authors (24:704). In addition, theaugmented audibility of distant sounds in rocky
landscapes can also be enhanced by the curved surfacesof the rock shelters themselves that allow impinging Figure 3 – Baume Peinte rock art site. (photosound waves to be reflected and concentrated at a focal
Ph. Hameau)point, like a parabolic mirror. A listener standing at thefocus point may experience louder sound levels than in adjacent positions (25:97-100).
How can we measure the auditory illusion of proximity to distant sound? How can we verify
whether there is a positive connection between this auditory illusion and the placement of rock art?
Within the framework of the SONART project, we were able to assess experimentally this relationshipby applying the Transmission Loss (TL) analysis at two rock art areas, Baume Peinte (26) in France(fig. 3) and Arroyo de San Serván (27) in Spain. TL analysis allows the identification of the soundlevel reduction (or attenuation) in decibels (dB) of a sound signal propagated between two points: thesound source and the receiver (28:175). Given a sound source in the landscape and a receiver placedin a rock art shelter, we assumed that the lower the attenuation, the higher the sound level that would
be perceived at the receiver position (shelter) and therefore the better the audibility of distant sounds.
In order to allow better comparisons, both shelters with and without rock art were measured. In ourfield tests, we used a portable loudspeaker placed in the landscape playing a 90.7 dB sine-sweep signal
ranging from 20 Hz to 20 kHz and an omnidirectional microphone connected to a digital recorderinstalled in the shelter. As a second step in our analysis we used TL analysis to compare the measured
attenuation at the receiver (shelter) to the attenuation that would be expected based on geometricalsound propagation in a free space (-6 dB per doubling of source distance, see (29)). If the measured
and predicted attenuation values are similar, it means that the rock art shelters are not different toother places in the landscape, i.e. that the audibility of distant sounds at the receiver (shelter) falls
within the average range of audibility in the area. In contrast, if the measured attenuation at thereceiver position (shelter) is below that expected, it means that the shelter possesses the ability toincrease the audibility of distant sounds. The final stage of our analysis was to compare values fromdifferent shelters (both with and without rock art) to verify whether there was a pattern of association
between shelters with rock art and the augmented audibility of distant sounds.
The data obtained from the two rock art areas provided significant results (Fig. 4). They indicate
that, given the same sound source, the signal received at rock art sites was louder than that received
at non-rock art shelters. In terms of perception of distant sounds, this means that non-decorated sites
offer the same degree of audibility as most other places in the landscape, while decorated sites are
exceptional in that they can amplify sounds coming from an external source. In summary, our results
indicate that the shelters at the Baume Peinte and Arroyo de San Serván rock art areas were possibly
selected because of their higher audibility values.

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5. CONCLUSIONS
Archaeoacoustics–
thearchaeological study of how
already disappeared societies madeuse of acoustics in the form ofmusic and sounds – is bringing
new light on the effect of thesenses in the past. In this article wehave shown that the results ofacoustic tests made in rock art
landscapes have revealed theimportance of acoustic effects intheCentralandWestern
Mediterranean
duringthe
Neolithic, a period in which theprehistoric communities of thatarea adopted agriculture in a longprocess covering the 7 th to the 4 thmillennia BC. Our tests in sites in
Italy, France and Spain point to thefact that there is a range of acoustic
phenomena relevant for the people
that inhabited each of the
Figure 4 - Chart representing measured sound levels in shelters
landscapes we have measured.
Those discussed in this article arewith rock art (triangle) and without rock art (circle) compared toechoes and the ability to receive
sounds coming from visually predicted sound levels due to the geometric spreading of the soundremote places. Yet, not all of them signal (90.7 dB at 1 m) (dotted line) (1) Abrigo de La Sierra de San
were present in the same location.
The communities living in the Serván; (2) Silletita del Rey; (3) Las Hogueras 2; (4) Las Hogueras
landscapeof
Baume
Brune 1; (5) Las Palomas 1; (6) Las Palomas 2; (7) Baume Peinte abri A;(Vaucluse, France) and Valle(8-14) Arroyo de San Serván rock shelters from S1 to S7; (15)d’Ividoro (Puglia, Italy) weresensitive to echoes, something we have been able to demonstrate thanks to the study of the Directionof Arrival (DOA) of echoes and sound reflections. Instead, those living in the mountainous area of
Alicante liked being heard at a distance, but not to start with (when the earliest Macroschematic style
was painted) but at a later time in a period between the Neolithic and the subsequent Chalcolithic(when Schematic rock art style became common). We have managed to prove this distinction by
studying the “acoustic arena” or the soundshed using SpreadGIS for ArcGis. In contrast to these twoareas in the Baume Peinte rock art site (also in Vaucluse, France) and in Arroyo de San Serván rockart landscape (Badajoz, Spain), a third distinctive acoustic effect was preferred at the time of choosing
the sites to be painted: the ability of these rock shelters to receive sounds coming from visually remoteplaces. We were able to discover this by undertaking the Transmission Loss (TL) analysis in which
we compared, as in previous cases, sites with and without rock art. These results show that working
in interdisciplinary teams – in our case archaeologists and acoustical engineers – brings new evidences
about the importance of the intangible among prehistoric societies. Our tests reveal new aspects ofthe past that were considered to be beyond analysis.

ACKNOWLEDGEMENTS
This article is a result of the ERC Artsoundscapes project (EC Grant agreement number: 787842).

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