**Contents**


## **About the Editor**

**Lamberto Tronchin** has served as Associate Professor at University of Bologna since 2011, where he is active in applied acoustics and energy efficiency research. His interests mainly regard room acoustics, where he has worked on developing new methods to measure acoustic quality in rooms, the design of theatres and auditoria, and the characterization of musical acoustics, where he has developed new vibro-acoustic parameters (IAR) and emulated the nonlinear sound behavior of musical instruments by means of Volterra series. With respect to energy efficiency, his research involves the study of new materials for improved energy efficiency of buildings. He is involved in both EU (POR FESR 2014–2020) and national (PRIN2015) projects. He is author of more than 200 papers and has served as plenary lecturer at numerous international congresses and institutions. He is also inventor of an international patent belonging to University of Bologna, namely "Method for artificially reproducing an output signal of a non-linear time invariant system". He is President of AES—Italian Section.

## *Editorial* **Special Issue on Musical Instruments: Acoustics and Vibration**

#### **Lamberto Tronchin**

Department of Architecture, University of Bologna, Via dell'Università 50, 47521 Cesena, Italy; lamberto.tronchin@unibo.it

Received: 6 May 2020; Accepted: 6 May 2020; Published: 9 May 2020

#### **1. Introduction**

The sound characteristics of musical instruments have been constantly growing in importance. Consequently, several congresses, workshops, and conferences have been organized in the last ten years. The studies on musical instruments, their mechanical behavior, sound emission, and characteristics started thousands of years ago, and among the physicists and mathematicians that addressed this matter, we should at least remember Leonardo da Vinci, with his experimental water organ, and Ernst Chladni, who discovered the nodal patterns on rigid surfaces, such as soundboards. The growing awareness of our intangible cultural heritage and the need to better understand our roots in the field of music have contributed to increasing the efforts to extend our knowledge in this field, defining new physical parameters, extending the analysis to other musical instruments, and developing new methods to synthesize sound from musical instruments using a simple keyboard.

These motivations led us to the proposal of a special issue called "Musical Instruments: Acoustics and Vibration" since we believe in the importance of musical acoustics within modern acoustics studies. In total, 13 papers were submitted and 8 of them were published, with an acceptance rate of 61.5%. Among all the papers published, one of them was classified as a review paper, while the rest were classified as research papers. According to the number of papers submitted, and the specificity of the musical acoustics branch within acoustics, it can be affirmed that this is a trendy topic in the scientific and academic community and this special issue on "Musical Instruments: Acoustics and Vibration" aims to be a future reference for the research that is to be developed in the next few years.

#### **2. Musical Instruments: Acoustics and Vibration**

Human beings started to play early musical instruments in the Neanderthal age [1], a fact that helps us to understand the importance of music for the world.

The sound characteristics of musical instruments, as well as their vibrational behavior, represent one of the most important and fascinating fields of acoustics, or even of applied physics.

This aspect is sometimes neglected (or at least not investigated enough) during the restoration of ancient masterpieces, even though it is well known that their sound production is something without equal and of inestimable value.

Following this concept, this special issue aimed to contribute to the knowledge of the acoustics of musical instruments. This goal was reached by proposing (or applying) new methods for characterizing the acoustics of musical instruments, by presenting studies on some specific art pieces, or by trying to illustrate some applications in sound synthesis.

The paper by Turk et al. [1] gives an interesting review of the historical debate about the findings of the "Neanderthal musical instrument" from the "Divje Babe I Cave" (Slovenia), one of the most ancient finds related with musical instruments, at least in Europe. This paper gives a proper idea about the ancient origin of this matter.

The two papers by Tronchin et al. [2,3] analyze completely different musical instruments. Starting from the definition of a new vibro-acoustical parameter called the intensity of acoustic radiation (IAR) [2], which was initially proposed for kettledrums, the studies were carried out to contribute to the knowledge of special and rare musical instruments. The first paper reports the results of both the modal analysis and IAR measured in a thar, a sithar, and a santoor, three important Persian musical instruments [3]. These outcomes give an idea of their behavior in response to increasing demand for knowledge of those musical instruments. The second paper describes the outcome of an experimental analysis carried out on a carabattola, a largely unknown ethnic Italian musical instrument, which used to be played in the Romagna region until the Second World War [4]. The analysis includes modal analysis and IAR measurements. It gives a unique contribution to the knowledge of this unique instrument.

The paper by Ibáñez-Arnal et al. [5] shifts the discussion to the physical properties of the material utilized for the realization of musical instruments, focusing on the carbon fiber reinforced epoxy (CFRE) prepregs, which could be used for new prototypes of new musical instruments. Undoubtedly, the physical characteristics of the materials strongly contribute to the overall assessment of the sound quality of the instruments.

The other papers focus on the application of the physics of musical instruments in the emulation of their sound production, especially during synthesis or recording. The paper by Moore [6] proposes a method for analyzing the dynamic range of sounds and music, whilst the paper by Papetti et al. [7] applies the outcomes of their previous studies into a new audio-tactile piano sample library, which is useful for real-time performances.

The last two papers analyze some specific aspects of this intriguing matter, especially from the signal processing perspective. In their paper, Jiang et al. [8] analyze the timbre perception features in musical motifs, whilst Ziemer and Plath [9] describe a method for simulating sound radiation using a microphone and loudspeaker array, going into detail about the necessary signal processing; the techniques used in both of these papers could be implemented when analyzing the non-linear components of the sound quality of musical instruments [10,11].

#### **3. Conclusions**

All the results presented and published in this special issue suggest that the acoustics and vibration of musical instruments is a relevant and popular topic in the scientific community. The results reported by all the authors increase the knowledge in this subject and contribute to a further understanding of this matter. This issue could become a starting point for further developments in the area of the physics of musical instruments.

**Funding:** This research was funded by Regione Emilia Romagna POR-FESR 2014-20 "SIPARIO" grant number PG/2018/632038.

**Acknowledgments:** The success of this special issue is strongly related to the huge work and the great contributions of all the authors. Furthermore, we acknowledge the hard work and the professional support of the reviewers and the editorial team of Applied Sciences. We are extremely grateful to all the reviewers involved in the issue for their time and their knowledge. We thank the assistant editors from MDPI that collaborated with us for their tireless support. We hope that the editorial process, starting from the submission and focusing on the review, was appreciated by all the authors, despite the final decisions. The real value of the time and the work spent in this process is found in the help provided to the authors to improve their papers.

**Conflicts of Interest:** The author declares no conflict of interest.

#### **References**


© 2020 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## *Review* **The Neanderthal Musical Instrument from Divje Babe I Cave (Slovenia): A Critical Review of the Discussion**

**Matija Turk 1,2,\*, Ivan Turk <sup>3</sup> and Marcel Otte <sup>4</sup>**


Received: 28 November 2019; Accepted: 26 January 2020; Published: 12 February 2020

**Abstract:** The paper is a critical review of different evidence for the interpretation of an extremely important archaeological find, which is marked by some doubt. The unique find, a multiple perforated cave bear femur diaphysis, from the Divje babe I cave (Slovenia), divided the opinions of experts, between those who advocate the explanation that the find is a musical instrument made by a Neanderthal, and those who deny it. Ever since the discovery, a debate has been running on the basis of this division, which could only be closed by similar new finds with comparable context, and defined relative and absolute chronology.

**Keywords:** Palaeolithic; Mousterian; Neanderthals; musical instrument; Divje babe I

#### **1. Introduction**

Discoveries that shed light, directly or indirectly, on the spiritual life of Neanderthals always attract great attention from the professional and lay public. One such find was unearthed in 1995 in Mousterian level D-1 (layer 8a), as a result of long-lasting (1979–1999) excavations in the Palaeolithic cave site of Divje babe I (DB) in western Slovenia, conducted by the ZRC SAZU Institute of Archaeology from Ljubljana. It was a left femur diaphysis, belonging to a one to two-year-old cave bear cub with holes (inventory no. 652), which resembled a bone flute (Figure 1). The object was found cemented into the breccia in the immediate vicinity of Neanderthal hearth, placed into a pit [1,2].

The excavation leader, I. Turk, proposed two possible explanations soon after its discovery: An artefact or a pseudo-artefact in the form of a gnawed and teeth-pierced femur diaphysis [1]. According to the first explanation, this find would be the oldest musical instrument [2–10]. The main surprise was not the great age of the find (at first 45,000 years, later 50,000–60,000 years), determined with 14C AMS, U/Th, and ESR on accompanying finds of charcoal, cave bear bones and teeth [8,9,11], but its undeniable attribution to Mousterian culture, i.e., Neanderthals. As such, it would represent significant evidence for existence of musical behaviour, long before the spread of anatomically modern humans across Europe that occurred roughly 40,000 years ago. In the last two decades, our view of Neanderthals has changed radically, but at the time of discovery, the idea of the existence of music in Neanderthal culture still seemed revolutionary.

**Figure 1.** The perforated femur diaphysis no. 652 from Divje babe I with two complete (nos. 2 and 3) and two partially preserved holes (nos. 1 and 4). Soon after discovery, the question arose whether it was a Neanderthal musical instrument or simply a bone pierced and gnawed by a carnivore (photo Tomaž Lauko, NMS).

#### **2. Contestable Explanation of the Carnivore Origin of the Holes**

The explanation of the find as a pseudo-artefact was immediately unilaterally taken over by F. d'Errico and colleagues [12], G. Albrecht and colleagues [13], P. G. Chase with A. Nowell [14], and later some others [15,16]. Thus, they negated the potential multilateral significance the find could have had for archaeology and other sciences. Advocates of the carnivore origin of the holes have not rested in the years since the discovery of specimen no. 652. They published a series of articles on the same topic. Among them, d'Errico was the only one who micro-scoped the find and explained the findings of the microscopy in accordance with his previous estimate [12], published in Antiquity in 1998 [17–19]. I. Turk with colleagues [10,20–25] (see also [26]) continuously argumentatively claimed that some of their statements, regarding their explanations about the origin of the holes and damages on the perforated bone, are incorrect [13,14,16,27–29]. To obtain more accurate explanation of the find, I. Turk and colleagues performed and published a series of experiments on perforating fresh brown bear femur diaphyses, using models of wolf, hyena, and bear dentitions (Figure 2), as well as replicas of Palaeolithic tools that were present in various Mousterian levels in DB [20,21,30,31]. Various musical tests of the find were also performed, which was reconstructed several times for this purpose [7,32–37].

After I. Turk and colleagues contested the arguments for the carnivore origin of the holes in numerous publications and offered arguments for their anthropic origin, it was up to advocates of the carnivore origin to refute their findings argumentatively, which they have not done so far. Their discussion of the find is distinctly one-sided and, with one sole exception [13], included no experiments. They presented certain erroneous claims to support their explanation, e.g., about the number of holes [14,19,27], contra [20,22,23], how the holes cannot be made in any other way than by drilling [13,28], contra [10,21,30], the placement of holes on the thinnest parts of the cortical bone [13,14,16], contra [22–24], actual possibilities of teeth grip in connection to holes and gnawing marks [13,14,16,18,19], contra [20,24,25], the sound capabilities of the musical instrument, if that is what the find actually is [19,27], contra [7,36–38], the inappropriateness of a cave bear femur as a support for a musical instrument in comparison to the supports from bird bones [29], contra [7,36–38], and about the frequency of gnawing marks [18] (Figure 9 from Reference [18]), Ref. [19], which in certain cases can also be explained as corrosion formations [10,39]. Corrosion was found to be especially strong in the layer containing the find [10,40].

**Figure 2.** Experimental piercing of a fresh femur of a young brown bear using a bronze model of hyena's dentition and the ZWICK/Z 050 machine for measuring compressive force (photo Ivan Turk, ZRC SAZU).

Supporters of the anthropic origin of the holes were also mistaken; e.g., about the original number of holes [4] and the original length of the musical instrument [35]. The first reconstructions of the find intended to research its musical capabilities, which places the mouthpiece into the large notch on the distal metaphysis, and which consequentially did not consider the opposite hole (at the time supposed to be a thumb hole because of its proximity to the mouthpiece), were also erroneous [31,32,34]. Due to the wrong orientation, the capability of the find as a musical instrument was reduced, and a remnant of the straight edge sharpened from both sides on the proximal part of the diaphysis, which functions on the musical instrument as the cutting edge of the mouthpiece, was overlooked [10,37] (Figure 9 from Reference [10]). It should be noted that we are dealing here with the first example of a bevelled mouthpiece edge. A bevelled mouthpiece edge, which enables better musical performance of the instrument is not known in later Upper Palaeolithic wind instruments, which are made of mammal limb bones. At already thin bone cortex of bird bones, the additional sharpening of the mouthpiece edge is not necessary to achieve better sonority.

When defining the holes on the femur diaphysis no. 652, which are the key component of all wind instruments, we have to start from certain findings of research of all cave bear finds, acquired with wet sieving of all sediments during the excavations of I. Turk, as well as from the findings of his fresh bone piercing experiments. In DB, the main damage to the bones was, in addition to humans, made by wolves (all remains belong to 30 individuals at the most) and not cave hyenas (zero specimens and no indirect proof, such as coprolites and digested bones) [25], contra [16]. The complete and partial holes on the femur diaphysis are undoubtedly of mechanical origin. Namely, both have a funnel-shaped inner edge, which occurs during piercing with a tooth or a pointed tool. Experiments show that the compression of the diaphysis with sharp (unworn) teeth or striking it with a pointed tool result in the longitudinal cracking of the compact bone [20]. Longitudinal cracks are present on some of the fossil bones that were undoubtedly pierced by carnivores [16] (Figures 5 and 6 from Reference [16]). Thus, the femur or some other tubular bone, with removed meta- and epiphyses, usually breaks in half longitudinally during piercing and widening of the hole(s) [16] (Figure 6 from Reference [16]). This is, however, not true for compression and piercing with strongly worn teeth and blunt pointed tools. A crack on the posterior side of the femur diaphysis no. 652 (Figure 1), which zigzags longitudinally from one end to the other is only superficial, and occurs during weathering in the course of fossilization. It is significantly different from the continuous, rectilinear in-depth crack that occurred on fresh bones during experimental piercing with metal models of carnivore dentition. Since the femur diaphysis no. 652 is not cracked in this way, solely worn teeth or blunt pointed tools can be considered to have produced the holes.

Both partial holes, which advocates of the carnivore origin of the holes considered to be evidence of bites, can be explained differently. V-shaped fractures start on both ends of the diaphysis in the partial hole, meaning that the holes came first and both fractures followed (Figure 1). If the fractures had been made simultaneously with the holes, three cracks would certainly have occurred: Two connected to the fracture and the third one on the diaphysis, with its starting point in the remains of the hole [13] (Figure 10.3 and p. 8, point 4 from Reference [13]). There is no third crack on either of the partial holes. Among 550 cave bear femur diaphyses without epiphyses, similar in size to specimen no. 652 from various layers in DB, only two are pierced and none with the V-fracture and a partial hole.

Judging from the shape and size of the holes, we agree with F. d'Errico [12,18] that they could have been pierced primarily with canines (Figure 3). C. Diedrich [16] believes that all holes in the bones of cave bear from different sites were made exclusively by premolars and molars. According to the first explanation, primarily an adult cave bear is possible, while, according to the second, it would have to be an adult cave hyena which was, like all hyenas, specialised for crushing bones. Frequent in vivo damage on the canine teeth of adult cave bears indicates their rough use. Measured forces from our experiments with models of various carnivore dentitions reveal that piercing with canine teeth takes one-time greater force than piercing with molars and two-times greater force if the tip of canine tooth is blunt [20]. Such forces are on the verge of the capability of the largest carnivores [41,42]. The oval shape of one of the holes and possible antagonist canine impression on the opposite, anterior side connected to it are not in line with the grip and occlusion of canine teeth [10,24], contra [18]. Congruity with the occlusion can be achieved only if the diaphysis is placed lengthwise to the teeth line in the sagittal direction. Such a bite would be highly unlikely, if possible at all. Due to the different shape of teeth tips and shape of the holes (Figure 3) and the unusual longitudinal femur grip considering the only possible dent (pitting after d'Errico [18] (Figure 9 from Reference [18]) of the antagonist tooth [25], cave hyena and the grip with so-called crushing teeth, which is referred to by C. Diedrich [16], is not an option. As stated above, there is also no direct and indirect evidence of the presence of hyena at DB. The same as for the bite of a hyena is true for the bite of a wolf, which is the second best represented carnivore at the site, next to cave bear. The latter is represented with several thousand individuals. It is also not possible to make a partial hole and a complete hole one beneath the other and simultaneously an emphasised depression right by hole no. 3 (Figure 3f, Figure 5) with just any tooth [24], contra [16,18].

**Figure 3.** Experimental holes on juvenile femur diaphysis of brown bear made by: (**a**) a bear's canine tooth, hole size 8.2 × 8.2 mm; (**b**) a hyena's lower canine tooth, hole size 6.5 × 8.3 mm; (**c**) a hyena's 3rd upper premolar, hole size 6.5 × 9.0 mm; (**d**) a hole made by a pointed stone tool and bone punch, size 6.0 × 7.4 mm (**e**,**f**) complete holes no. 2 (size 8.2 × 9.7 mm) and 3 (size 8.7 × 9.0 mm) on the femur from DB no. 652 (ZRC SAZU, Archive of Institute of Archaeology).

Many juvenile femur diaphyses, and other tubular bones of extremities in DB and elsewhere have a bigger distal or proximal semi-circular notch, which is typical carnivore damage. Such a notch also occurs on the distal metaphysis of femur no. 652 from DB (Figure 1). Considering the circumstances, it can be attributed to a wolf, with which P.G. Chase and A. Nowel also agree [14]. Undisputable traces of gnawing on both ends of the diaphysis cannot be linked with certainty to the occurrence of both complete holes and at least one partial hole [10,24], contra [18]. Since it was possible for carnivores to damage Palaeolithic osseous artefacts and leave traces of teeth on them, which is proven by some of the gnawed osseous points [20] (Figure 20 from Reference [20]), ([43] p. 257, Photo 1), this could have happened to femur diaphysis no. 652 at some later time. Most probably, it was at that time that both V-fractures with the starting point in the hole, from which only a partial hole could have remained both times, could have been made.

#### **3. Anthropic Origin of the Holes**

Due to the shortcomings the explanation of F. d'Errico and his colleagues regarding the carnivore origin of the holes and damage on femur diaphysis no. 652, more attention is warranted to the alternative explanation of the find and findings connected to it, which are based on the results of appropriate experiments and on indirect evidence from archaeological finds in Mousterian levels of DB.

When piercing bones Neanderthals could imitate carnivores and use pointed tools and the dynamic force of strikes, instead of the compression force of teeth. Holes can be carved into the diaphysis with pointed stone tools [30] found in the Mousterian levels of DB [44]. The bone does not crack during this procedure. The edge of such holes is irregular and serrated, just as with holes on the specimen no. 652, while the edge of holes made by a tooth is generally smooth, depending on the thickness of the cortical bone (Figure 3). Clearly recognisable tool marks are not always present as was attested by F. d'Errico. Namely, six experimentally carved holes were put under microscopic examination. Tool marks were detected on only half of them [19]. However, characteristic damage, such as a broken tip and other fractures, does occur on the tools. Such damage is also present on some of the Mousterian tools from DB [10,20,31] (Figure 4). Holes can also be made with a blunt ad hoc bone punch, struck with a wooden hammer, if a dent has previously been carved into the cortical bone. The holes produced by this technique are morphologically identical to the holes on the specimen no. 652 and completely lack the conventional manufacture marks [21].

**Figure 4.** Tools suitable for perforating cortical bone: Pointed stone tools (the first on the right has a broken tip) and bone punches from the Mousterian layers of Divje babe I (photo Tomaž Lauko, NMS).

Whether the bone will crack depends on the shape of the punch point (blunt or sharp). In Mousterian levels of DB, beside rare undisputable fragments of bone and antler points, some ad hoc punches with rounded tips were found [23,45] (Figure 4).

At first glance, such artificially made holes on the diaphysis resemble holes made with teeth. The latter are almost always in the vicinity of the epiphyses and only exceptionally on juvenile diaphyses of the approximately same size, such as specimen no. 652 [16]. This is conditioned with the ability of large carnivores, i.e., physical restriction regarding the grip and muscle strength, and with the thinner cortical bone near epiphyses. Unlike animals, man was able to pierce holes along the entire femur diaphysis, regardless of the thickness of the cortical bone. While puncturing bones, people could choose among significantly more methods than animals, which instinctively always do exactly the same. Therefore, in the case of the artefact, it is easier to substantiate the problematic damage, including the above-mentioned depression near hole no. 3 on the posterior side of the diaphysis. Namely, in its vicinity, there are two parallel micro-scores on the abraded surface of the cortical bone (Figure 5), which could be interpreted as cut marks made by stone tools. These micro-scores are never mentioned by advocates of the carnivore origin of the holes. The possibility that people used a femur, the distal end of which was previously damaged by carnivores, is not ruled out. Regarding the absence of other microscopic traces related to manufacture, they could have been erased due to extremely strong corrosion in the layer comprising the find. Only the more distinct scores were preserved, as well as the dent(s) (pitting after F. d'Errico [18]) made by teeth, which, considering their position, cannot be connected with certainty to the production of holes by compression and piercing with teeth. Due to their orientation and shape, all scores and dents, recognized by d'Errico and colleagues, cannot be attributed to carnivores. Carnivores make scores with their teeth that are perpendicular or slightly oblique to the axis of the diaphysis. They are not able to make a score subparallel to the axis of the diaphysis with their bites [10] (Figure 9 from Reference [10]). Some of the dents must have been made by corrosion, which was not considered by d'Errico and colleagues [39]. At least one longitudinal score could be a tool mark.

**Figure 5.** Depression near hole no. 3 on the posterior side of the diaphysis and location of two parallel micro-scores on the abraded surface of cortical bone (marked with an arrow) (ZRC SAZU, Archive of Institute of Archaeology).

The strongest argument for the thesis that, the DB perforated femur is indeed a deliberately crafted musical instrument, comes from experimental musical research on a reconstructed find. It was determined that the artificially transformed juvenile diaphysis is ideal in shape and length for the performance of music using a special playing technique [36,37]. Following the directions of I. Turk [22], in 2010, the missing parts, and both partial holes of the original, were reconstructed on the left cave bear juvenile femur of the size of the original (Figure 6). Due to practical reasons, the mouthpiece of

the reconstructed musical instrument was made on the straight edge of the widened part of medullary cavity. This edge fits lips better than the edge of the narrowed part. Later, professional musician L. Dimkaroski established that on the original, the remnant of the straight part of this edge is bevelled on both sides of the cortical bone and could as such function as the perfected cutting edge of the mouthpiece [37]. Considering the position of the edge of the mouthpiece and torsion of the diaphysis, the diaphysis of the left femur is also handier for a right-handed musician, while a right femur diaphysis would be more suitable for a left-handed player. All contemporary music genres can be played on the thus reconstructed musical instrument. The comparative acoustic analysis and tests revealed its great musical capability. With a musical capability of 3<sup>1</sup> <sup>2</sup> octaves [37] (a CD in the appendix), the reconstructed musical instrument from Divje babe I surpasses the musical capability of reconstructed Aurignacian osseous wind instruments, made from the bones of large birds [38,46,47].

**Figure 6.** Reconstruction of the Neanderthal musical instrument from Divje babe I. The reconstructed parts are in white plaster. The position of the bevelled cutting edge of the mouthpiece is marked by an arrow (photo Tomaž Lauko, NMS).

#### **4. Conclusions**

If the holes on femur no. 652 are not equated with the obvious and frequent impressions of teeth, i.e., punctures with the impressed cortical bone [16] (Figure 4: 9b–11b; Figure 7: 2b from Reference [16]) – on meta- and epi-physes from cave bear sites, as is done by d'Errico and some of his adherents, the find does not have a suitable comparison in collections of pierced limb bones of cave bear [16,48]. The exception is the diaphysis of a juvenile femur with three holes from the Aurignacian cave site Istállósk˝o in Hungary [6,49], which is currently not considered to be a potential musical instrument, due to numerous more convincing new finds of Aurignacian wind instruments in cave sites of the Swabian Jura [50] and the French Pyrenees [51].

Currently, this unique find fulfils all conditions on the basis that it can be defined as the oldest known musical instrument. These are: clear archaeological and stratigraphic context [44], dating [8,9,11], explanation of manufacturing [21], musical verification [36,37], ([47] (p. 458), contra [19] p. 55), and good comparisons in later periods [52]. In a preserved state, the find is not suitable for playing music. Playing was enabled by the reconstruction based on concrete data and the well-founded assumption that the reconstructed parts were removed by a wolf, prior to cementation. Similarly damaged is the Upper Palaeolithic musical instrument from the loess layer in the open-air site Grubgraben (Austria) [52]

(Figures 2 and 3 form the Reference [52]). Due to the fine texture of the loess, the damage on the Grubgraben flute could have occurred exclusively prior to its inclusion into the sediment. Presumably, it was damaged by a wolf occasionally feeding on the remains of the prey of Palaeolithic hunters.

The find of the Mousterian musical instrument from DB has certain advantages in relation to other, declaratively the oldest similar instruments from the sites in the Swabian Jura, in regards to context, stratigraphy, reconstruction, and morphometric characteristics. The context and stratigraphy, supported by indirect 14C AMS, U/TH, and ESR dates [8,9,11], are indisputable because the find, firmly cemented into the breccia, could not move within the sediment or be mixed with older finds due to detected gaps in sedimentation. One of them occurred above the cemented part of layer 8, where the musical instrument was found [53].The leading Aurignacian artefact – the point with the split base – found in the youngest Pleistocene combined layer 2–3, two metres higher, enables the cultural paralleling of Aurignacian level with sites of the Swabian Jura and simultaneously indisputably proves the greater relative age of specimen no. 652, in comparison to the finds of musical instruments in the Swabian Jura and elsewhere [50].

The reconstruction of the DB musical instrument is more reliable than the reconstructions of Swabian finds, in which either the length or the mouthpiece are not preserved [46,47,50,54]. The morphometric characteristics of the DB musical instrument are such that, even on the basis of physical laws, despite the smaller length, they enable a greater musical capability in comparison to Swabian finds. Excuses of everything being dependent on the interpreter are only partly valid. This has also been confirmed by the unpublished musical experiments of professional musician L. Dimkaroski (personal communication) with the replica of Swabian wind instrument GK 1 and comparative acoustic calculations of F. Z. Horusitzky [38] for Swabian instruments GK 1 and GK 3.

The musical instrument from Divje babe I, which predates 50 ka, firmly supported with a Mousterian (Neanderthal) context and chronology, remains the strongest material evidence so far for Neanderthal musical behaviour. According to the present knowledge and archaeological context of the find, there are no obstacles for the find to be interpreted as a Neanderthal musical instrument.

**Author Contributions:** Conceptualization, M.T. and I.T.; methodology, I.T.; investigation, I.T. and M.T.; writing original draft preparation, M.T., I.T. and M.O.; writing—review and editing, M.T.; supervision, M.O. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors acknowledge the financial support from the Slovenian Research Agency (P6-0283 and P6-0064). We also thank ZRC SAZU Institute of Archaeology for part-financing from its current assets.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## *Article* **The** *Carabattola***—Vibroacoustical Analysis and Intensity of Acoustic Radiation (IAR)**

#### **Lamberto Tronchin 1,\*, Massimiliano Manfren <sup>2</sup> and Vincenzo Vodola <sup>1</sup>**


Received: 21 August 2019; Accepted: 15 January 2020; Published: 16 January 2020

**Abstract:** Among the studies of musical instruments, one important, sometime underestimated discipline, is represented by ethnomusicology. The acoustic analyses on ethnic musical instruments (M.I.) are much more infrequent if compared to those on classical M.I. This article deals with the vibro-acoustic analysis on one of the most unknown ethnic, Italian M.I., i.e., the *carabattola* (also called *battola*), which used to be played in Italy until the late 1960s during the Holy Thursday before Easter. The study includes modal analysis and Intensity of Acoustic Radiation measured on an original *carabattola*, which was played in the Romagna area until the early twentieth century. After a brief overview about the theory of acoustic and vibrational analysis on musical instruments, the Intensity of acoustic radiation and its correlation with modal analysis are recalled, based on previous studies. In the experimental part of the article, the measurements conducted on the *carabattola* are described. Afterwards, the results obtained both from modal analysis and IAR measurements are analyzed and compared with other measurements previously conducted on musical (particularly percussion) instruments and commented.

**Keywords:** sound efficiency; intensity of acoustic radiation (IAR); *Carabattola*; modal analysis

#### **1. Introduction**

The physics of musical instruments represents one of the most intriguing field of acoustics, especially for those scientists that are normally involved in the preservation of cultural heritage. There are different techniques to study the vibro-acoustical behavior of musical instruments; between them, modal analysis and acoustic radiation are usually used. However, some other techniques have been developed starting from these fundamental methods.

The studies on the physics and acoustics of musical instrument that were carried out in the last 30 years normally regarded classical musical instruments, especially violins [1], piano [2,3], wind instrument [4], and other musical instruments. Only a few studies have analyzed other musical instruments [5]. This was due to the request of knowledge of the sound characteristics of those instruments from lutherie, industrial manufactory companies, researchers, curators, collectors, museums, historians, musicians, theatre companies and all parties involved with preservation and restoration of those important, valuable objects. One more reason for studying the sound characteristics of musical instruments from the physical perspective is the emulation of their sound characteristics [6] by means of measurements of impulse responses [7] and convolution with dry music, including nonlinear properties [8,9].

On the other hand, other musical instruments have been developed or invented for several reasons, sometimes very different from each other, but the scientific community did not pay proper attention to them. The *carabattola*, sometime called *battola*, belongs to this category of musical instruments (M.I.).

In order to determine the acoustic characteristics of M.I., acoustic radiation (like acoustic impedance or admittance) is one of the most important physical parameters utilized to characterize their properties. Sound radiation is closely linked to modal patterns, and a connection should therefore have occurred between resonance frequencies and sound production in vibration constructions. Evidence of the negative correlation between acoustic radiation and Frequency Response Function (FRF) of membranes or plates in instruments, such as piano and harpsichord, has been identified in earlier studies by Suzuki [10] and Giordano [11]. The complexity of pianos and harpsichord was perhaps the reason for the negative correlation, and their complex structure could have impeded their understanding of their sound radiation.

Percussion instruments, on the other side, are comparatively straightforward, and frequency response studies, modal analysis, acoustic radiation and the relationship between FRF and noise radiation can be readily discovered [12]. The comparison between experimental modal patterns and previously outcomes could suggest the most appropriate measurement technique for characterizing vibro-acoustical properties of musical instruments. For tympani, where sound generation and modal analysis are related, a vibro-acoustic parameter was needed, capable of correctly correlating noise output with FRF. Applications of this extend beyond musical acoustics into the modeling of musical instruments in auditoria. The search of the link between sound radiation and modal analysis in musical instruments has been an issue for several years.

## **2. The** *Carabattola*

In western music there are plenty of musical instruments normally played since the beginning of prehistoric ages. Most of them were idiophonic M.I., in which the sound was obtained by hitting the bore with wooden or (later) metallic elements. Moreover, there are several instruments which were invented not for generating pitched music but rather for producing acoustic effects, mainly for specific religious circumstances. Among them, in Mediterranean Europe, several ethnographic instruments have been utilized since the early middle ages almost up to the present. The *carabattola* is one of these M.I.

The *carabattola*, also known as *battola*, is an extremely uncommon idiophone instrument of ethnographic music. Its name recalls the origin of sound (acoustic) emission, i.e., it must be hit by some metallic components in order to produce acoustic effect. This instrument used to be performed only during the Holy Week before Easter, and it may have Byzantine origins. With his handler, the player retains the instrument and rapidly turns the *carabattola* right and left. In this way, the movement causes a clapper to hit in rapid sequence alternatively two metallic little circles, inserted in the wood. Thus, the clapper looks like a knocker and the acoustic effect appears.

The *carabattola* belongs to a series of musical instruments, all of them played during Holy Week before Easter in Mediterranean Europe. Other similar musical instruments are the *Cembalo* or *Crotalo* as Francesco Saverio Quadria, already reported in 1734 [13], normally made in oak or chestnut wood. Some other similar musical instruments, like *Matracula*, (Figure 1) are still used, although seldomly, in some parts of Italy such as the Sardinia region [14].

**Figure 1.** *Matracula*, a percussion instrument still in use in Sardinia (Italy).

The *Carabattola*, as well as the other similar musical instruments specifically realized for Holy Week, does not provide a specific pitched sound, but rather a particular acoustic effect, which increases the particular religious atmosphere, together with the chanting and the incense. These specific characteristics are the reasons for the decision to carry out vibrational and acoustic characterization of the wooden element (the "soundboard").

In this paper, an original example of *Carabattola* is analyzed. This instrument belongs to the Madonna del Carmine Church in Bagnacavallo, Ravenna, Northern Italy. It was locally called *Scarabàtla* and used to be played roughly until 1970. The chest (probably made by wood from fruit trees) is approximately 25 cm width, 50 cm length, 2.2 cm thickness, whilst the metallic (perhaps iron) circles are 2.0 cm width. It should be emphasized that this tool provides a background noise, partly comparable to the noise of a grater and not a real sound (as usually expected).

#### **3. Material and Methods**

#### *3.1. Acoustic Radiation*

The efficiency of acoustic radiation is a measure of the effectiveness of a vibrating surface in generating sound power. It could be defined by the relationship:

$$
\sigma = \frac{W}{\rho\_0 c S \sqrt{v\_n^2}} \tag{1}
$$

in which *W* is the sound power radiated by a surface with area S, which could be obtained by integrating the far-field intensity over a hemispherical surface centered on the panel, and - *v*2 *n* is the space-averaged value of the time-averaged normal distribution of velocity [15]. This parameter could be utilized for searching a link between movement (vibration) and acoustic generation (sound).

Various measuring techniques that are helpful for noise emission analysis could be acquired from this overall concept, ranging from frequent applications in noise emissions in machinery, to rare examples on musical instruments. In musical acoustics, previous investigations have been carried out on piano and harpsichord soundboards using different technique. Wogram used the parameter *F*/*v,* defining F as the excitation force and v as the resulting velocity at the point of excitation [16]. In his experiments, he found a maximum at a frequency that is close to or below 1 kHz and that falls sharply below 100 Hz and above 1 kHz. He discovered that it falls typically by a factor of 10, as the frequency varies between 1 and 5 kHz. On the other hand, the "surface intensity method" was identified by Suzuki [10] and defined by the equation:

$$I = \operatorname{Re} [p(\alpha/j\omega^\*)/2] \tag{2}$$

where *I* represents the average intensity in time, perpendicular to the vibrating surface, measured in near field (about 30 cm from the radiating surface); ω is the angular frequency; Re and \* are the real part and the complex conjugate of a complex number; p and a are the pressure and the normal acceleration at the measuring point. Further, Giordano used the parameter *p*/*v* where p is the sound pressure measured in near field, and v is the velocity of the soundboard [11]. At around 1 kHz in all sampled frequencies *p*/*v* is larger and drops below a few hundred hertz and above 5 kHz.

It is essential to note that all these studies have one prevalent outcome: The frequencies of resonance have not coincided with those of acoustic emission, but they often have an adverse correlation.

#### *3.2. Intensity of Acoustic Radiation—IAR*

From the experiment described above, the Intensity of Acoustic Radiation (IAR) parameter was defined in 2005 as the space averaged amplitude of the cross-spectrum between the sound pressure generated from the vibration of the surface and the velocity of the surface vibration [17]:

$$IAR(\omega) := \quad \langle P(\omega) \ast \mathbf{V}(\omega) \rangle \tag{3}$$

For the measurement, an omnidirectional microphone is required. According to Suzuki, the microphone must have been positioned in a specific point which corresponds to about one-quarter of the wavelength of the frequency corresponding to the earliest mode. If tympani are involved, this distance is approx. 25 cm over the membrane.

The measurements should be carried out in a slightly reverberating space where average radiation induced by early modes is easily achieved via the reverberation time. The acoustics chamber has no effect on the readings at higher frequencies. In addition, the measurements are enhanced by space-averaging of information carried out by shifting transductors through the instruments. It should be considered that other vibroacoustic parameters have been obtained starting from IAR, applied in very different field of acoustics, as building acoustics [18].

#### *3.3. I.A.R.: Previous Measurements*

When IAR was defined, in order to verify the robustness of the parameter, two distinct percussion instruments were used to measure IAR. These instruments were two kettledrums. The first was a 25-inch (approx. 65 cm) kettledrum plexiglass Adam with a Remo mylar skin and central reinforcement tuned at about 166 Hz (corresponding to E), whilst the second one was a copper 25-inch Ludwig kettledrum, which was tuned to roughly 145 Hz (D-corresponding) with a mylar skin without a central reinforcer.

The tympani measurements were carried out in two different ways. A hammer with an accelerometer was used in the first case, whilst the hammer was replaced by a shaker in the second case. The microphone was in the same position in both cases. In order to verify the outcomes from previous researches, up to 15 modes were obtained and compared with literature. This allowed verifying the accuracy of the measurements. Figure 2 reports the results obtained in 2005 [17].

**Figure 2.** Tympani: (**a**) FRF compared with *p*/*v*; (**b**) FRF compared with IAR.

## **4. Measurements on** *Carabattola*

The measurements on the *carabattola* were carried out in a similar way as the tympani. In one of two metal circles, the shaker excited the instrument, with the microphone positioned approximately 25 cm above. All measures were carried out in the same room of the tympani, with the same acoustic boundary conditions as described in the article [17].

Modal analyzes were also performed in this case. The measurements were conducted positioning the accelerometers on 24 positions and stored (Figure 3). In a further step, all the measurements were post processed in order to obtain FRF and modal patterns. The findings are quite different from the kettledrum, because the sound generation varies significantly from the tympani. The IAR is measured by the proportion *p*/*v* and FRF as depicted in Figure 4. Due to the increase in modal density at higher frequencies, the chart is restricted to 1 kHz. The modal patterns from 107 to 344 Hz, measured in the instrument, are reported in Figure 5.

**Figure 3.** The measurements on the *carabattola*.

**Figure 4.** *Carabattola*: FRF compared with *p*/*v* and IAR.

The match between IAR and FRF in *carabattola* is not as strong as in kettledrums. However, the negative correlation is not so obvious from FRF to *p*/*v*. The unique properties of sound emission of *carabattola*, which significantly differ from the tympanum, should explain this result.

**Figure 5.** *Cont.*

**Figure 5.** Modal patterns for the *carabattola* (from top left to bottom right): 107 Hz, 150 Hz, 193 Hz, 247 Hz, 297 Hz, 322 Hz.

The IAR measurements on the *carabattola* were also carried out together with modal analysis as previously made for the kettledrums. As mentioned earlier, the sound pressure p, as previously reported from Suzuki, Giordano and Tronchin, was evaluated in the near field at 25 cm from the instruments, maintaining the correct distance already proposed in early studies.

#### **5. Results**

#### *Analysis of Measured Data*

Comparing the results obtained on the *carabattola* with the results obtained on the kettledrums, the following points could be underlined.

In the case of the tympani, the negative correlations between FRF and IAR are very high, and at the same time, the two respective graphs are almost coincident. It should be noted that tympanum has a clearly defined sound pitch, mainly due to the membrane motion.

On the other hand, different results were carried out in the case of *carabattola*, as the mechanism of sound generation differs considerably from the tympanum. Figure 5 shows the first six modal *carabattola* patterns. It is important to note that the metallic plate where the knocker strikes the instrument affects the motion of the sound chest from the evaluation of these patterns. In view of the relationship between FRF and *p*/*v*, only partly a negative connection is noted, particularly at medium-low frequencies. In comparison, they are only partly linked, when comparing the two graphs FRF and IAR. The two charts seem like they are shifted of a small frequency range, even if they are much more linked than FRF and *p*/*v*.

The tympanum mainly produces sound from the membrane, which is a very straightforward perception of the pitch caused by the membrane vibration. On the other hand, in the *carabattola* the chest and metal knocker produce a sound that is not perceived as a particular pitch.

In the case of tympani, IAR, FRF and *p*/*v* are highly correlated each other, as almost all sound generation comes from the membrane (where the sound velocity v is measured), whilst the correlation in *carabattolas* is not as obvious as the sound generation comes from wood alone.

#### **6. Discussion**

Two types of percussion instruments, two tympani and one *carabattola*, were carried out with acoustic radiation measurements and modal analysis, as proposed by many authors in previous articles. In both cases, the instruments were excited by means of a shaker, connected with a thin metallic bar. In a previous paper, the shaker resulted better than the head impedance hummer, as the resonance of the bar that connects the shaker with the instruments was discovered at approximately 3 kHz.

The mappings of individual vibration modes were very clear for all the instruments, and in the case of tympani, the frequency ratios were approximately consistent with the theory. For circular and mixed vibration modes, a high degree of correspondence was obtained, while the diametric modes produced slightly less frequencies than the theoretical ones. Due to the typical noise generated in the *carabattola*, modal pattern mapping was not so evident like in the tympanum.

The tympanum generates its sound mainly from the membrane and has a very little thickness if compared with its surface and could be considered bi-dimensional. The membrane is elastically deformable, and its vibration is only slightly damped. Conversely, the *carabattola* is made of a wooden body having a relevant thickness of 2.2 cm, not elastically deformable and cannot be considered bi-dimensional. The body is not elastically deformable, and its vibration is strongly damped.

Acoustic radiation has been evaluated in two different ways in all musical instruments. The first step was to calculate the complex ratio (*p*/*v*) between sound pressure and vibration velocity of the principal vibration components of the instrument. This is the method used by Giordano.

In the second step, an amplitude of a space-averaged of cross spectrum (*p* · *v*) between sound pressure and the vibrational speed of the membranes or chest was calculated at a fixed point 25 cm over the instruments. This is the parameter known as Intensity of Acoustic Radiation (IAR).

The IAR thus led to a parameter that was able to correctly associate the vibration of plate or membranes with the sound production. This relationship is remarkable for tympani, while the relationship is not so strong for *carabattola*. In the first situation, IAR and FRF are very correlated and only partly linked in the second situation. We have not considered the effect of the metal knocker, because our focus was in the vibroacoustic behavior of the soundboard.

Considering the modal patterns obtained from modal analysis and reported in Figure 5, it is noticeable that there are no clear modal patterns obtained from the analysis. This result is coherent with the sound behavior of the musical instrument, which is not characterized by a specific pitch but rather produces a strong peculiar noise which recalls a *grater.* Since there is not any specific pitch in the sound emission, there are no frequencies that emerged from the music spectrum. Moreover, the thickness of the soundboard, which is considerably higher than that of other wooden musical instruments or even plates, causes an early damping of the sound (or noise) emission that is compensated by the quick movement of the metallic handle, which hits the soundboard with a very high frequency.

In other words, the sound analysis carried out on the *carabattola* does not give evidence of any specific frequency but rather looks partially similar to a flatten spectrum without any decay, similarly to percussion instruments like a wooden scraper. Consequently, the modal patterns which resulted from the analysis resulted having an irregular shape, which is completely different from the membrane of the tympanum.

#### **7. Conclusions**

The *carabattola* is an almost unknown idiophone musical instrument that used to be played only during Holy Week in Mediterranean Europe. Few examples of this musical instrument are actually conserved in Italy, and no acoustic analyses are available for it. This paper attempted to describe its vibroacoustic behavior by means of some specific acoustic measurements: modal analysis and intensity of acoustic radiation. These methods have been already utilized in other musical instruments, as the kettledrum.

In the *carabattola*, comparing the FRF graph and *p*/*v,* it can be noted how frequencies of resonance often differ from those of acoustic emission. When IAR is applied, resonance frequencies completely match those of noise emissions, and the forms of the two graphs are comparable.

In the case of tympani, this was particularly evident: The IAR parameter was well related to the response function of frequencies, and therefore, it resulted preferable to *p*/*v*. IAR is a parameter between acoustic intensity and acoustic radiation, so it is suitable to measure the sound generating characteristics of musical instruments with vibrating soundboards (i.e., FRF). This parameter could also be used to describe and identify the directivity of musical instruments, essential both for architectural acoustics and for procedures of auralization.

In the case of the kettledrum, the links between FRF, IAR and modal analysis were very high, because of the clear subjective pitch of the M.I. In the case of the *carabattola*, where no pitch is detected, the correlations between FRF, IAR and modal patterns resulted very low. These results underline the link existing between IAR, modal patterns and pitch of the vibrating surface: Where no pitch is detected, low correlations occur between IAR and FRF, and modal analysis becomes less important.

The results obtained in the *carabattola* showed that modal patterns were not clearly identified as in the violin or kettledrum, and its sound emission was characterized by an almost uniformed frequency distribution, which typically characterizes idiophones.

**Author Contributions:** L.T. provided the funding, made the measurements and the results. M.M. contributed to the writing of the paper. V.V. finalized the paper including its formatting. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Italian Government in the framework of PRIN 2015. within the project "Research for SEAP: a platform for municipalities taking part in the Covenant of Mayors".

**Acknowledgments:** The Authors wish to thank Elisa Ferri for her precious help during the measurements and post processing.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

#### *Article*
