With Halloween coming tomorrow, what better time than now to delve into the eerie world of archaeoacoustics? In the Acoustics Today article, “Archaeoacoustics: Re-Sounding Material Culture,” author Miriam A. Kolar delves into the sonic secrets of archaeological materials, unearthing long-forgotten forms of communication, and reanimating the silenced voices of the past.
Archaeoacoustics is an emerging field that transcends disciplines, allowing people to explore the significance of sound across time and cultures. It goes beyond mere acoustics and harnesses science, engineering, and the humanities to interpret archaeological findings. With a focus on experimentation, analytical models, and computational reconstructions, archaeoacousticians aim to unlock the sensory implications of ancient materials.
Imagine yourself atop a 3,000-year-old stone structure, towering above ancient plazas, listening to the haunting echoes of giant conch shell horns known as pututus. It’s not a ghostly apparition; it’s archaeoacoustics in action. In a spine-tingling experiment at Chavín de Huántar, Peru, researchers set out to measure sound transmission through these prehistoric sound devices. As they perceived the echoes “swirling around from all directions,” they recorded the sound and its return, revealing an auditory landscape we can scarcely imagine.
Archaeoacoustics is all about mapping the potential for sonic communication, assessing what could be heard and from where. By employing scientific methodologies and integrating information from site archaeology, researchers can test historical claims and offer empirical evidence for sound dynamics. Whether exploring pututus in the Andes or the enigmatic carnyx in ancient Scotland, archaeoacoustics reveals the extraordinary potential of sound to bridge the gap between past and present.
As we prepare for Halloween’s eerie nights, remember that the mysteries of archaeoacoustics are just one example of how science can unveil the spectral sounds of the past. This field offers us a fascinating journey into the world of archaeology, combining the haunting echoes of history with the precision of acoustic science.
As Halloween approaches, it’s the perfect time to dive into the mysterious world of bat robots in this Acoustics Today article, “The Evolution of Bat Robots.” The ability of bats to navigate their environment using ultrasound has fascinated scientists for decades, and the mystery of how they process this information has drawn researchers from various fields. It’s no wonder that engineers have been lured into this world, attempting to replicate the biosonar capabilities of bats through a variety of “bat robots.”
Despite decades of research, the intricacies of bat biosonar remain mostly uncharted. Continuous advancements in recording and data analytics technologies promise to unlock more insights into the world of bat robots. These insights will likely drive further evolution in the field. Researchers are on the cusp of developing more integrated systems that combine encoding and extraction of sensory information. These mechanical marvels, inspired by the eerie elegance of bats, may hold the key to autonomous drones capable of navigating the dark forests, just like their natural counterparts.
The Acoustics Today articleweaves together a captivating story of technological evolution, highlighting the challenges, breakthroughs, and intriguing possibilities that lie ahead. If you’re curious about how bats’ extraordinary biosonar abilities are inspiring cutting-edge drones and robotic systems, read the full article for free at AcousticsToday.org. It’s a journey that promises to leave you in awe of both nature and human ingenuity. Happy Halloween!
Miriam Kolar, Ph.D. – firstname.lastname@example.org AC# 2255, PO Box 5000 Architectural Studies Program & Dept. of Music Amherst College Amherst, MA 01002
Popular version of paper 4pAAa2. Pututus, Resonance and Beats: Acoustic Wave Interference Effects at Ancient Chavín de Huántar, Perú Presented Thursday afternoon, October 30, 2014 168th ASA Meeting, Indianapolis See also: Archaeoacoustics: Re-Sounding Material Culture
Excavated from Pre-Inca archaeological sites high in the Peruvian Andes, giant conch shell horns known as “pututus” have been discovered far from the tropical sea floor these marine snails once inhabited.
Fig. 1a: Excavation of a Chavín pututu at Chavín de Huántar, 2001. Photo by John Rick.
Fig. 1 B-C: Chavín pututus: decorated 3,000-year-old conch shell horns from the Andes, on display at the Peruvian National Museum in Chavín de Huántar. Photos by José Luis Cruzado.
At the 3,000-year-old ceremonial center Chavín de Huántar, carvings on massive stone blocks depict humanoid figures holding and perhaps blowing into the weighty shells. A fragmented ceramic orb depicts groups of conches or pututus separated from spiny oysters by rectilinear divisions on its relief-modeled surface. Fossil sea snail shells are paved into the floor of the site’s Circular Plaza.
Fig. 2: Depictions of pututus players on facing stones in the Circular Plaza at Chavín. Photo by José Luis Cruzado & Miriam Kolar.
Pututus are the only known musical or sound-producing instruments from Chavín, whose monumental stone architecture was constructed and used over several centuries during the first millennium B.C.E.
Fig. 3 (VIDEO): Chavín’s monumental stone-and-earthen-mortar architecture towers above plazas and encloses kilometers of labyrinthine corridors, room, and canals. Video by José Luis Cruzado and Miriam Kolar, with soundtrack of a Chavín pututu performed by Tito La Rosa in the Museo Nacional Chavin.
How, by whom, and in what cultural contexts were these instruments played at ancient Chavín? What was their significance? How did they sound, and what sonic effects could have been produced between pututus and Chavín’s architecture or landform surroundings? Such questions haunt and intrigue archaeoacousticians, who apply the science of sound to material traces of the ancient past. Acoustic reconstructions of ancient buildings, instruments, and soundscapes can help us connect with our ancestors through experiential analogy. Computer music pioneer Dr. John Chowning and archaeologist Dr. John Rick founded the Chavín de Huántar Archaeological Acoustics Project (https://ccrma.stanford.edu/groups/chavin/) to discover more.
Material traces of past life––such as artifacts of ancient sound-producing instruments and architectural remains––provide data from which to reconstruct ancient sound. Nineteen use-worn Strombus galeatus pututus were unearthed at Chavín in 2001 by Stanford University’s Rick and teams. Following initial sonic evaluation by Rick and acoustician David Lubman (ASA 2002), a comprehensive assessment of their acoustics and playability was made in 2008 by Dr. Perry Cook and researchers based at Stanford’s Center for Computer Research in Music and Acoustics (CCRMA).
Fig. 4: Dr. Perry Cook performs acoustic measurements of the Chavín pututus. Photo by José Luis Cruzado.
Transforming an empty room at the Peruvian National Museum at Chavín into a musical acoustics lab, we established a sounding-tone range for these specific instruments from about 272 Hz to 340 Hz (frequencies corresponding to a few notes ascending from around Middle C on the piano), and charted their harmonic structure.
Fig. 5 (VIDEO): Dr. Perry Cook conducting pututu measurements with Stanford CCRMA team. Video by José Luis Cruzado.
Back at CCRMA, Dr. Jonathan Abel led audio digital signal processing to map their strong directionality, and to track the progression of sound waves through their exponentially spiraling interiors. This data constitutes a digital archive of the shell instrument sonics, and drives computational acoustic models of these so-called Chavín pututus (ASA 2010; Flower World 2012; ICTM 2013).
Where does data meet practice? How could living musicians further inform our study? Cook’s expertise as winds and shells player allowed him to evaluate the Chavín pututus’ playability with respect to a variety of other instruments, and produce a range of articulations. Alongside the acoustic measurement sessions, Peruvian master musician Tito La Rosa offered a performative journey, a meditative ritual beginning and ending with the sound of human breath, the source of pututu sounding. This reverent approach took us away from our laboratory perspectives for a moment, and pushed us to consider not only the performative dynamics of voicing the pututus, but their potential for nuanced sonic expression.
Fig. 6 (VIDEO): Tito La Rosa performs one of the Chavín pututus in the Museo Nacional Chavín. Video by Cobi van Tonder.
When Cook and La Rosa played pututus together, we noted the strong acoustic “beats” that result when shell horns’ similar frequencies constructively and destructively interfere, producing an amplitude variation at a much lower frequency. Some nearby listeners described this as a “warbling” or “throbbing” of the tone, and said they thought that the performers were creating this effect through a performance technique (not so; it’s a well-known acoustic wave-interference phenomenon; see Hartmann 1998: 393-396).
Fig. 7 (VIDEO): José Cruzado and Swiss trombonist Michael Flury demonstrate amplitude “beats” between replica pututus in Chavín’s Doble Ménsula Galley. Video by Miriam Kolar.
If present-day listeners are unaware of an acoustics explanation for a sound effect, how might ancient listeners have understood and attributed such a sound? A pututu player would know that s/he was not articulating this warble, yet would be subject to its strong sensations. How would this visceral experience be interpreted? Might it be experienced as a phantom force?
The observed acoustic beating effect between pututus was so impressive that we sought to reproduce it during our on-site tests of architectural acoustics using replica shell horns. CCRMA Director Dr. Chris Chafe joined us, and he and Rick moved through Chavín’s labyrinthine corridors, blasting and droning pututus in different articulations to identify and excite acoustic resonances in the confined interior “galleries” of the site.
Fig. 8: CCRMA Director Chris Chafe and archaeologist John Rick play replica pututus to test the acoustics of Chavín’s interior galleries. Photos by José Luis Cruzado.
The short reverberation times of Chavín’s interior architecture allow the pututus to be performed as percussive instruments in the galleries (ASA 2008). However, the strong modal resonances of the narrow corridors, alcoves, and rooms also support sustained tonal production, in an acoustically fascinating way. Present-day pututu players have reported the experience of their instruments’ tones being “pulled into tune” with these architectural resonances. This eerie effect is both sonic and sensed, an acoustic experience that is not only heard, but felt through the body, an external force that seemingly influences the way the instrument is played.
Fig. 9 (AUDIO MISSING): Resonant compliance: Discussion of phantom tuning effect as Kolar and Cruzado perform synchronizing replica pututus in the Laberintos Gallery at Chavín. Audio by Miriam Kolar.
From an acoustical science perspective, what could be happening? As is well known from musical acoustics research (e.g., Fletcher and Rossing 1998), shell horns are blown-open lip-reed or lip-valve instruments, terminology that refers to the physical dynamics of their sounding. Mechanically speaking, the instrument player’s lips vibrate (or “buzz”) in collaborative resonance with the oscillations produced within the air column of the pututu’s interior, known in instrument lingo as its “bore”. Novice players may have great difficulty producing sound, or immediately generate a strong tone; there’s not one typical tendency, though producing higher, lower, or sustained tones requires greater control.
Experienced pututu players such as Cook and La Rosa can change their lip vibrations to increase the frequency––and therefore raise the perceived pitch––that the shell horn produces. To drop the pitch below the instrument’s natural sounding tone (the fundamental resonant frequency of its bore), the player can insert a hand in the lip opening, or “bell”, of the shell horn. Instrument players also modify intonation by altering the shape of their vocal tracts. This vocal tract modification is produced intuitively, by “feel”, and may involve several different parts of that complex sound-producing system.
Strong architectural acoustic resonance can “couple”, or join with the air column in the instrument that is also coupled to that of the player’s vocal tract (with the players lips opening and closing in between). When the oscillatory frequencies of the player’s lips, those within the air column of his or her vocal tract, the pututu bore resonance, and the corridor resonance are synchronized, the effect can produce a strong sensation of immersion in the acoustic environment for the performer. The pututu is “tuned” to the architecture: both performer and shell horn are acoustically compliant with the architectural resonance.
When a second pututu player joins the first in the resonant architectural location, both players may share the experience of having their instrument tones guided into tune with the space, yet at the same time, sense the synchrony between their instruments. The closer together the shell openings, the more readily their frequencies will synchronize with each other. As Cook has observed, “if players are really close together, the wavefronts can actually get into the shells, and the lips of the players can phase lock.” (Interview between Kolar & Cook 2011: https://ccrma.stanford.edu/groups/chavin/interview_prc.html).
Fig. 10 (VIDEO): Kolar and Cruzado performing resonance-synchronizing replica pututus in the Laberintos Gallery at Chavín. Video by Miriam Kolar.
From the human interpretive perspective, what might pututu players in ancient Chavín have thought about these seemingly phantom instrument guides? A solo pututu performer who sensed the architectural and instrumental acoustic coupling might understand this effect to be externally driven, but how would s/he attribute the phenomenon? Would it be thought of as embodied by the instrument being played, or as an intervention of an otherworldly power, or an effect of some other aspect of the ceremonial context? Pairs or multiple performers experiencing the resonant pull might attribute the effect to the skill of a powerful lead player, with or without command of supernatural forces. Such interpretations are motivated by archaeological interpretations of Chavín as a cult center or religious site where social hierarchy was developing (Rick 2006).
However these eerie sonics might have been understood by people in ancient Chavín, from an acoustics perspective we can theorize and demonstrate complex yet elegant physical dynamics that are reported to produce strong experiential effects. Chavín’s phantom forces––however their causality might be interpreted––guide the sound of its instruments into resonant synchrony with each other and its architecture.
(ASA 2002): Rick, John W., and David Lubman. “Characteristics and Speculations on the Uses of Strombus Trumpets found at the Ancient Peruvian Center Chavín de Huántar”. (Abstract). In Journal of the Acoustical Society of America 112/5, 2366, 2002.
(ASA 2010): Cook, Perry R., Abel, Jonathan S., Kolar, Miriam A., Huang, Patty, Huopaniemi, Jyri, Rick, John W., Chafe, Chris, and Chowning, John M. “Acoustic Analysis of the Chavín Pututus (Strombus galeatus Marine Shell Trumpets).(Abstract). Journal of the Acoustical Society of America, Vol. 128, No. 2, 359, 2010.
(Flower World 2012): Kolar, Miriam A., with Rick, John W., Cook, Perry R., and Abel, Jonathan S. “Ancient Pututus Contextualized: Integrative Archaeoacoustics at Chavín de Huántar, Perú”. In Flower World – Music Archaeology of the Americas, Vol. 1. Eds. M. Stöckli and A. Both. Ekho VERLAG, Berlin, 2012.
(ICTM 2013): Kolar, Miriam A. “Acoustics, Architecture, and Instruments in Ancient Chavín de Huántar, Perú: An Integrative, Anthropological Approach to Archaeoacoustics and Music Archaeology”. In Music & Ritual: Bridging Material & Living Cultures. Ed. R. Jiménez Pasalodos. Publications of the ICTM Study Group on Music Archaeology, Vol. 1. Ekho VERLAG, Berlin, 2013.
(Hartmann 1998): Hartmann, William M. Signals, Sound, and Sensation. Springer-Verlag, New York, 1998.
(ASA 2008): Abel, Jonathan S., Rick, John W., Huang, Patty P., Kolar, Miriam A., Smith, Julius O. / Chowning, John. “On the Acoustics of the Underground Galleries of Ancient Chavín de Huántar, Peru”. (Abstract). Journal of the Acoustical Society of America, Vol. 123, No. 3, 605, 2008.
(Fletcher and Rossing 1998): Fletcher, Neville H., and Thomas D. Rossing. The Physics of Musical Instruments. Springer-Verlag, New York, 1998.
(Rick 2006): Rick, John W. “Chavín de Huántar: Evidence for an Evolved Shamanism”. In Mesas and Cosmologies in the Central Andes (Douglas Sharon, ed.), 101-112. San Diego Museum Papers 44, San Diego, 2006.
Background Music has the potential to evoke powerful emotions, both positive and negative. When listening to an enjoyable piece or song, an individual can experience intense, pleasurable “chills” that signify a surge of dopamine and activations in certain regions in the brain, such as the ventral striatum1 (see Fig. 1). Conversely, regions of the brain associated with negative emotions, for instance the parahippocampal gyrus, can activate during the presentation of music without harmony or a distinct rhythmic pattern2. Prior research has shown that the nucleus accumbens (NAcc) in the ventral striatum specifically activates during reward processing3, even if the stimulus does not present a tangible benefit, such as that from food, sex, or drugs4-6.
Figure 1: A cross-section of the human brain detailing (left) the ventral striatum, which houses the nucleus accumbens (NAcc), and (right) the parahippocampal gyrus.
Even subtle changes in acoustic (sound) stimuli can affect experiences positively or negatively. In terms of concert hall design, the acoustical characteristics of a room, such as reverberance, the lingering of sound in the space, contribute significantly to an individual’s perception of music, and in turn influences room acoustics preference7-8. As with the case for music, different regions of the brain should activate depending on how pleasing the stimulus is to the listener. For instance, a reverberant stimulus may evoke a positive emotional response in listeners that appreciate reverberant rooms (e.g. a concert hall), while negative emotional regions may be activated for those that prefer drier rooms (e.g. a conference room). The identification of which regions in the brain are activated due to changes in reverberance will provide insight for future research to investigate other acoustic attributes that contribute to preference, such as the sense of envelopment.
Stimuli The acoustic stimuli presented to the participants ranged in levels of perceived reverberance from anechoic to very reverberant conditions, e.g. a large cathedral. Example stimuli, which are similar to those used in the study, can be heard using the links below. As you listen to the excerpts, pay attention to how the characteristics of the sound changes even though the classical piece remains the same.
Example Reverberant Stimuli:
The set of stimuli with varying levels of reverberation were created by convolving an anechoic recording of a classical excerpt with a synthesized impulse response (IR) that represented the IR of a concert hall. The synthesized IR was double-sloped (see Fig. 2a) such that early part of the response was consistent between the different conditions, but the late reverberation differed. As shown in Fig. 2b the late parts of the IR vary greatly, while the first 100 milliseconds overlap. The reverberation times (RT) of the stimuli varied from 0 to 5.33 seconds
Figure 2: Impulse responses for the four synthesized conditions: (L) the total impulse response, (R) Time scale from 0 to 1 seconds to highlight the early part of the IR.
Functional magnetic resonance imaging (fMRI) was used to locate the regions of the brain that were activated by the stimuli. In order to find these regions, the images obtained due to the musical stimuli are each compared with the activations resulting due to control stimuli, which for this study were noise stimuli. Examples of control stimuli that are matched to the musical ones provided earlier can be heard using the links below. The noise stimuli were matched to have the same rhythm and frequency content for each reverberant condition.
Example Noise Stimuli:
Experimental Design A total of 10 stimuli were used in the experiment: five acoustic stimuli and five corresponding noise stimuli, and each stimulus was presented eight times. Each stimulus presentation lasted for 16 seconds. After each presentation, the participant was given 10 seconds to rate the stimulus in terms of preference on a five-point scale, where -2 was equal to “Strongly Dislike,” 0 was “Neither Like Nor Dislike,” and +2 was “Strongly Like.”
Results The following data represent the results of one participant averaged over the total number of repeated stimuli presentations. The average preference ratings for the five musical stimuli are shown in Fig. 3. While the majority of the ratings were not statistically different, the general trend is that the preference ratings were higher for the stimuli with the 1-2 second RTs and lowest for the excessively long RT of 5.33 seconds. These results are consistent with a pilot study that was run with seven subjects, and in particular, the stimulus with the 1.44 second RT was found to have the highest preference rating.
Figure 3: Average preference ratings for the five acoustic stimuli.
The fMRI results were found to be in agreement for the highest rated stimulus with an RT of 1.44 seconds. Brain activations were found in regions shown to be associated with positive emotions and reward processing: the right ventral striatum (p<0.001) (Fig. 4a) and the left and right amygdala (p<0.001) (Fig. 4b). No significant activation were found in regions shown to be associated with negative emotions for this stimulus, which supports the original hypothesis. In contrast, a preliminary analysis of a second participant’s results possibly indicates that activations occurred in areas linked to negative emotions for the lowest-rated stimulus, which is the one with the longest reverberation time of 5.33 seconds.
Figure 4: Acoustic Stimulus > Noise Stimulus (p<0.001) for RT = 1.44 s showing activation in the (a) right ventral striatum, and (b) the left and right amygdala.
Conclusion A first-level analysis of one participant exhibited promising results that support the hypothesis, which is that a stimulus with a high preference rating will lead to activation of regions of the brain associated with reward (in this case, the ventral striatum and the amygdala). Further study of additional participants will aid in the identification of the neural mechanism engaged in the emotional response to stimuli of varying reverberance.
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2. Blood, AJ, et al. Emotional responses to pleasant and unpleasant music correlate with activity in paralimbic brain regions. Nature Neuroscience. 1999, Vol. 2, 4, pp. 382-387.
3. Schott, BH, et al. Mesolimbic functional magnetic resonance imaging activations during reward anticipation correlate with reward-related ventral striatal dopamine release. Journal of Neuroscience. 2008, Vol. 28, 52, pp. 14311-14319.
4. Menon, V and Levitin, DJ. The rewareds of music listening: Response and physiological connectivity of the mesolimbic system. NeuroImage. 2005, Vol. 28, pp. 175-184.
5. Salimpoor, VN., et al. Anatomically distinct dopamine release during anticipation and experience of peak emotion to music. Nature Neuroscience. 2011, Vol. 14, 2, pp. 257-U355.
6. Salimpoor, VN., et al. Interactions between the nucleus accumbens and auditory cortices predict music reward value. Science. 2013, Vol. 340, pp. 216-219.
7. Beranek, L. Concert hall acoustics. J. Acoust. Soc. Am. 1992, Vol. 92, 1, pp. 1-39.
8. Schroeder, MR, Gottlob, D and Siebrasse, KF. Comparative sutdy of European concert halls: correlation of subjective preference with geometric and acoustic parameters. J. Acoust. Soc. Am. 1974, Vol. 56, 4, pp. 1195-1201.