Archaeoacoustics around the World: A Literature Review (2016–2022)

Abstract

Acoustics has been integrated with archaeology to better understand the social and cultural context of past cultures. Specifically, public events such as rituals or ceremonies, where an appreciation of sound propagation was required to hold an event. Various acoustic techniques have been used to study archaeological sites, providing information about the building characteristics and organizational structures of ancient civilizations. This review aims to present recent advances in Archaeoacoustics worldwide over the last seven years (2016–2022). For this purpose, one hundred and five articles were identified and categorized into two topics: (1) Archaeoacoustics in places, and (2) Archaeoacoustics of musical instruments and pieces. In the first topic, three subtopics were identified: (1) measurement and characterization of places, (2) rock art, and (3) simulation, auralization, and virtualization. Regarding the first subtopic, it was identified that the standards for reverberation times in enclosures are generally applied in their development. In the second subtopic, it was determined that the places selected to make paintings were areas with long reverberation time. The last subtopic, simulation, auralization, and virtualization, is the area of most remarkable growth and innovation. Finally, this review opens the debate to seek standardization of a measurement method that allows comparing results from different investigations.

1. Introduction

Archaeoacoustics is the study of archaeological sites through their sound and acoustic characteristics [1,2,3]. Namely, it is the application of acoustics in archaeological spaces [1]. On the one hand, acoustics is a branch of physics that studies the production and propagation of sound waves. Furthermore, it could be defined as the study of the generation, transmission, and reception of energy found in the form of vibratory waves that move through matter, including fluids, solids, or gases [4]. On the other hand, archaeology could be defined as a social science that studies the material remains left by past societies [5]. Additionally, as Subias [6] states, historic archaeology could be defined as the study of the past that has a written record to base research on, while prehistoric is defined as the study of the past that does not have a written record.

Recently, the number of studies on sound generation and propagation in worldwide archaeological sites has been increasing since they have revealed the social and cultural behaviors of ancient societies [1,2]. For example, ancient builders considered auditory conditions (e.g., nature sounds) to make their constructions [2]. In addition to acoustics, archeology has also been supported by physics, anthropology, and architecture to study ancient daily activities, including all those where sound was a key element, such as music production [7].

So far, Archaeoacoustics has had a wide variety of study aims, including socio-political studies to obtain information among different cultures [8]. To meet these aims, it has been necessary to establish methodologies that allow acoustic characterization in archaeological sites with different conditions (e.g., level of conservation). For this purpose, researchers have undertaken their field investigations in several ways, which hinders the reporting of repeatable, reproducible, and comparable results. Therefore, it is required to standardize the acoustic procedures to ensure similar quality characterizations of archaeological zones [9,10]. In this review, the following acoustic parameters were identified as the most used to characterize archeological sites:

• Reverberation time (T₆₀)—A parameter to measure how long a sound remains after the sound source is turned off. It is measured in seconds and is obtained when the sound energy reduces by 60 dB. Similarly, sound energies reduced by 30 dB (T₃₀) and 20 dB (T₂₀) allow the measurement of the reverberation time when it is not possible to have the energy decay at 60 dB [11]. The T₆₀ calculation formula is:

  $${\mathrm{T}}_{60}=0.161\frac{\mathrm{V}}{\mathrm{A}}$$

  (1)

  where:
  • V: room volume is in m³;
  • A: total absorption of the room in Sabins.
• Sound pressure level (SPL)—A parameter to indicate the magnitude of a sound field measured in dB [11]. The SPL formula is:

  $$\mathrm{SPL}=20{\log }_{10}\left(\frac{\mathrm{P}}{{\mathrm{P}}_{\mathrm{o}}}\right)$$

  (2)

  where:
  • P: sound pressure in Pascals;
  • P_o: reference sound pressure (20 µPascals).
• Early decay time (EDT)—A parameter defined as six times elapses since the sound is off until the SPL drops 10 dB, measured in seconds [11].
• Strength (G)—A parameter defined as the difference between the SPL produced by an omnidirectional source at a point in the room and the SPL produced by the same source located in a free field and measured at a distance of 10 m [11]. The strength formula is:

  $$\mathrm{G}=10\log \frac{{{\displaystyle \int }}_0^{\infty }{\mathrm{P}}^2\left(\mathrm{t}\right)\mathrm{dt}}{{{\displaystyle \int }}_0^{\infty }{\mathrm{P}}_{\mathrm{A}}^2\left(\mathrm{t}\right)\mathrm{dt}}$$

  (3)

  where:
  • P(t): instantaneous sound pressure in Pascals;
  • P_A(t): reference sound pressure in Pascals.
• Articulation loss of consonants (ALcons)—A parameter defined as an indication of the loss of speech intelligibility that occurs in complex acoustic environments [12]. The ALcons formula is:

  $$\mathrm{ALcons}\approx 0.652{\left(\frac{{\mathrm{r}}_{\mathrm{LH}}}{{\mathrm{r}}_{\mathrm{H}}}\right)}^2{\mathrm{T}}_{60}\%$$

  (4)

  where:
  • ${\mathrm{r}}_{\mathrm{LH}}$: distance sound source-listener;
  • ${\mathrm{r}}_{\mathrm{H}}$: reverberation radius or, critical distance ${\mathrm{r}}_{\mathrm{R}}$, in case of directional sound sources.
• Speech transmission index (STI)—A parameter between 0 and 1 that indicates the speech transmission quality [11]. The STI formula is:

  $$\mathrm{STI}=\frac{{\left(\overline{\mathrm{S}/\mathrm{N}}\right)}_{\mathrm{ap}}+15}{30}$$

  (5)

  where:
  • ${\left(\overline{\mathrm{S}/\mathrm{N}}\right)}_{\mathrm{ap}}$: total apparent noise/signal.
• Clarity50 (C50) measures the clarity or intelligibility of speech. It is expressed in decibels. It is related to the sound energy that arrives at a listener within 50 milliseconds [11]. The C50 formula is:

  $${\mathrm{C}}_{50}=10\log \frac{{{\displaystyle \int }}_0^{0.05}{\mathrm{P}}^2\left(\mathrm{t}\right)\mathrm{dt}}{{{\displaystyle \int }}_{0.05}^{\infty }{\mathrm{P}}^2\left(\mathrm{t}\right)\mathrm{dt}}$$

  (6)

  where:
  • P(t): instantaneous sound pressure in Pascals.
• Definition (D50) is similar to C50 but is expressed in percentage [12]. The D50 formula is:

  $${\mathrm{D}}_{50}=\frac{{{\displaystyle \int }}_0^{0.05}{\mathrm{P}}^2\left(\mathrm{t}\right)\mathrm{dt}}{{{\displaystyle \int }}_0^{\infty }{\mathrm{P}}^2\left(\mathrm{t}\right)\mathrm{dt}}$$

  (7)

  where:
  • P(t): instantaneous sound pressure in Pascals.
• Clarity80 (C80) measures the clarity or intelligibility of music. It is expressed in dB. It is related to the sound energy that arrives at a listener within 80 milliseconds [11]. The C80 formula is:

  $${\mathrm{C}}_{80}=10\log \frac{{{\displaystyle \int }}_0^{0.08}{\mathrm{P}}^2\left(\mathrm{t}\right)\mathrm{dt}}{{{\displaystyle \int }}_{0.08}^{\infty }{\mathrm{P}}^2\left(\mathrm{t}\right)\mathrm{dt}}$$

  (8)

  where:
  • P(t): instantaneous sound pressure in Pascals.

In addition to all these acoustic parameters, the most common method used to reproduce audio spatially has been Ambisonics. This method refers to the representation of directional auditory data by using spatial sampling that is then resynthesized through a finite number of point sources [13]. Despite being extensively studied from an architectural standpoint, the acoustic characterization of many archaeological sites has not been thoroughly examined.

Learning more about acoustics and sounds in archaeological sites could provide valuable insights into the cultures and customs of ancient inhabitants. This knowledge not only serves as cultural heritage for humanity, but it is also a way to bring closer the thoughts and worldview of the people who lived in those sites.

However, despite the numerous archaeological sites found worldwide (e.g., Teotihuacan in Mexico, Easter Island in Chile, The Ta Prohm in Cambodia, The Luxor temple in Egypt, Longmen Grottoes in China, and Machu Picchu in Peru), the study of Archaeoacoustics is limited or even nonexistent. Therefore, it is important to consider the most recent scientific advances in this field to identify current research gaps and unanswered questions.

Therefore, the main goal of this paper is to review papers published between 2016 and 2022 in the field of Archaeoacoustics. This review aims to identify recent advances in this field, including (1) the applied technologies to characterize, simulate, or recreate ancient places, (2) the methodologies followed to do so (Section 2), (3) the most relevant findings related to Archaeoacoustics worldwide (Section 3), and (4) a critical opinion about advances towards Archaeoacoustics characterization of worldwide sites (Section 4 and Section 5).

2. Methods

This literature review was carried out based on four steps proposed by [14]. These authors established four main steps:

• Step 1: Conduct a Search. The databases were analyzed, and those relevant to the study area were established. It was decided to use seven search engines: ScienceDirect, Springer, Scopus, AES E-Library, JASA, Web of Science, and ProQuest. The search was limited to the last seven years [15], 2016 to 2022.
• Step 2: Identify Keywords. Three keywords were considered for this study, and the following string resulted: Archaeoacoustics OR ((“acoustic measurement” OR “acoustic measurements”) AND (“archaeological site” OR “archaeological sites”)) AND NOT underwater. This string was also used in Spanish to obtain information about Latin America and Spain.
• Step 3: Review Abstracts and Articles. Three hundred and eighty-six articles were identified, considering all the criteria mentioned above. Chapter thesis, news, and repeated articles were excluded, resulting in one-hundred and five research items.
• Step 4: Document Results. Every identified article was analyzed, and the findings were summarized and synthesized. The content was encompassed under two categories: (1) Archaeoacoustics in places (ninety-four of them), and (2) Archaeoacoustics of musical instruments and pieces (eleven of them).

Paper Records

The study of acoustics at archaeological sites has been an ongoing field of research for many years. One of the pioneers in the field of Archaeoacoustics is David Lubman, who was interviewed in [16] about echoes. In 1998, two investigations were identified in Mexico. The first one, conducted by David Lubman [17], examines the chirped echoes produced in the pyramids of Chichen Itza. The second one is related to a visual simulation of the acoustic ray hitting. This effect refers to one of the walls of a pyramid at Cholula, which was a novel methodology at the time [18]. Nowadays, it is possible to simulate the acoustics of complete architectural spaces, even considering the construction materials used. As a case in point, a virtual reconstruction and auralization of a medieval cathedral in southern Italy was achieved by [19]. Another example is the study conducted by [20], where the acoustics of two Roman theaters were characterized. Furthermore, acoustic analysis of painted rocks from ancient times have been conducted to investigate whether acoustics were present in ancient cultures (e.g., musical behaviors) [21]. The role of music in ancient cultures has been of great interest, and various studies on musical behaviors and instruments have been conducted, such as the acoustic analysis of wind musical instruments found in Calakmul (Campeche, Mexico) [22].

In line with the literature selected for this review, the following topics and subtopics were considered:

• Acoustics in archaeological places

  ○

  Measurements and characterizations

  ○

  Rock art

  ○

  Simulation, auralization, and virtualization

• Musical instruments and pieces

3. Main Findings

3.1. Acoustics in Archaeological Places

3.1.1. Measurement and Characterization

Most investigations on this topic involve conducting measurements on-site at the selected locations, with the exception of the research in [23,24], where a replica of the site was created first. Most of these studies comply with the ISO 3382-1:2009 norm [25], except for [26]. Table 1 and Table 2 present the information related to the characterization of all these worldwide places. Additionally, the research of Đorđević [27] was identified, where a study of vessels was conducted inside churches in Serbia to determine if they were designed and used for acoustic purposes within buildings. The authors found that there is a certain regularity in the position of the vessels that influences the acoustics of the places they studied. Additionally, the investigation of D’Orazio [28] presents a review of acoustic theater designs from 15th to 19th century minor Italian Opera houses. Finally, three investigations using infra and ultrasound and vibration methods were identified to obtain the acoustic characteristics of the sites [29,30,31,32].

Table 1. Archaeoacoustics measurement and characterization of historical worldwide places.

Country	Place	Original Place or Replica	Atmospheric Conditions (Temperature, Humidity, Wind Speed)	Room Type	Microphone and Sound Source Localization	Achaeological Type
Malta [33]	Ħal Saflieni Hypogeum	Original	Humidity and temperature were controlled, limiting the number of people at the place.	Close room	Four microphone positions and three sound source positions.	Prehistoric
Greece [34]	Acheiropoietos Basilica and the Cathedral of Hagia Sophia	Original	Measurements made at the same time of the day to have the same temperature and humidity.	Close room	Multiple microphone positions and source positions.	Historic
Peru [26]	The Huánuco Pampa	Original	Estimated temperature around 12–16 °C and the humidity between 47–68%.	Open space	Eight microphone positions and three sound source positions.	Prehistoric
Spain/England/Cyprus [35]	Spanish Prehistoric Painted Caves/Stonehenge/Paphos Theater	Original	-	Open space	-	Prehistoric
England [23]	Stonehenge–Scale model	Replica	-	Open space	34 microphone positions and six sound source positions.	Prehistoric
Italy [36]	Theater of Tyndaris	Original	The temperature was between 26.2–28.8 °C. The humidity was between 45–79.4%. The wind speed was between 0.25–1.7 m/s.	Open space	Nine microphone positions and two sound source positions.	Prehistoric
Spain [20]	Theater of Carthago Nova and the theater of Saguntum	Original	The temperature was 32 °C in Cartagena and 21.6 °C in Saguntum. The humidity was 49% in Cartagena and 46.3% in Saguntum. The wind speed was less than 0.5 m/s.	Open space	20 microphone positions in Carthago, 34 microphone positions in Saguntum, and three sound source positions.	Historic
Mexico [37]	Mexico City Cathedral	Original	The temperature was 21 °C. The humidity was between 34–35%.	Close room	Several microphones position. Several sound sources position.	Historic
Spain [38]	Roman theater and amphitheater of Segobriga, Spain	Original	The temperature was between 27.9–44.3 °C. In the theater and 18.4–41.7 °C in the amphitheater. The relative humidity range in the theater was 17–44.4% and in the amphitheater was 21.2–76.1%) with air velocity less than 0.5 m/s.	Open space	Three sound sources, 19 microphone positions in the theater; three sound sources and 15 microphone positions in the amphitheater.	Historic
Turkey [39]	Eight historical mosques in the Aegean Region	Original	-	Close room	Several microphone positions around the mosques, and one sound source was in front of the mihrab in each case.	Historic
Italy [40]	Teatro Nuovo of Spoleto and the Teatro Alighieri of Ravenna	Original	-	Close room	The sound source was placed on the stage and in the orchestra pit. Receivers were placed in 38 places in the stelas and 14 in balconies. The sound source was placed at 1.4 m from the floor and the receivers were at the height of 1.2 m on stalls and boxes.	Historic
Russia [41]	Rachmaninov Hall, which is part of the Moscow Conservatory	Original	-	Close room	The dodecahedron sound source was placed in the center of the stage at 1.5 m and 10 microphones were distributed in the audience area. A microphone was placed inside the vessel in the middle lower row.	Historic
Spain [42]	Palace of Charles V	Original	The temperature, humidity and barometric pressure was measured.	Open space	Three source positions were selected on the stage. Sixteen microphone positions on the stage and ten in the audience.	Historic
France [43]	Cathédrale Notre-Dame, Paris	Original	Temperature and humidity were measured.	Close room	The sources were near the altar and the microphones in the central nave.	Historic
Spain [44]	Cathedral of Cadiz	Original	-	Close room	The sound source positions were the high altar, the pulpit, the choir, the organ position, the retrochoir, and the crypt.	Historic
El Salvador [24]	Replica of the Ceren Temazcal	Replica	-	Close room	Not reported.	Prehistoric
Italy [45]	Catholic church of Budrio	Original	-	Close room	One source was placed in the nave, another under the dome, and the last in the middle of these areas.	Historic
India [46]	Kanheri Caves	Original	-	Close room	Some points around the caves.	Historic
Italy [47]	Teatro 1763 in Bologna	Original	-	Close room	The sound source was located in two positions on the stage and microphones in eleven different positions in the stalls and the first gallery.	Historic
Egypt [48]	20 Iwan masjids (mosques)	Original	The ambient temperature and humidity were monitored and recorded.	9 semi-closed and 11 closed	A minimum of twelve decay curves, distributed randomly across the rooms (or half of the symmetric rooms when it is applicable), were collected (6 per sound source location).	Historic
Italy [49]	Catacombs of San Callisto, Catacombs of San Gennaro, Catacombs of Vigna Cassia	Original	-	Close room	The sound sources were positioned at different points in the catacombs.	Historic
Italy [50]	Teatro Comunale in Trevisa Vittorio Emanuele in Messina, Teatro Galli in Rini	Original	-	Close room	The records were obtained in 25 measuring points in stalls and balconies. The sound source was located on the stage and orchestra pit.	Historic

Table 2. Systems and procedures used in measurements and characterization of studies reported in Table 1.

Country	Measurement Information	Registration System		Measured Parameter	Reverberation Time Reported (Seconds)
		Hardware	Software
Malta [33]	The microphones and loudspeakers were placed at different points, and a frequency sweep from 20 Hz to 20 kHz was used.	Portable sound source and two omnidirectional microphones.	Odeon, Sonic Visualizer, and Audacity	T30, T20, EDT, D50, C7, C50, C80, STI, SPL and ALcons	T30 up to 16 s at 63 Hz in Ħal Saflieni Hypogeum
Greece [34]	An 8 s logarithmic sine sweep from 20 Hz to 24 kHz was used and played ten times per microphone location.	Measurement microphones and directional powered speaker system.	-	EDT, C80, T60	T60 2.72 s at 500 Hz in Acheiropoietos Basilica. T60 2.86 s at 500 Hz in Cathedral of Hagia Sophia
Peru [26]	An exponential sinusoidal sweep was used.	Audio recorder, portable sound source, and sound source connected to a smartphone.	Octave, Matlab, Sonic Visualizer, and Audacity	SPL	-
Spain/England/Cyprus [35]	-	Omnidirectional sound source.	Odeon	T30, EDT	EDT 1.54 s average (125–1000 Hz) in Pasiega Turret Cave. EDT 1.79 s average (125–2000 Hz) in Paphos Theatre
England [23]	A scale model replica of Stonehenge was made and characterized. A one-second logarithmic sine sweep was used.	Measurement microphone and tweeters sound sources.	-	T30, EDT, D50, G	T30 0.6 s average in Stonehenge scale model
Italy [36]	An impulse sound produced by a firecracker blast was used, and an exponential sine sweep signal reproduced by the loudspeaker was used.	Measurement condenser microphone, omnidirectional sound source, and a firecracker blast.	Dirac, Aurora, and Matlab	T20, C80, C50, G	T20 0.57 s average in Theatre of Tyndaris
Spain [20]	A frequency sweep from 63 Hz to 16 kHz was used.	Ambisonic microphones, Head Acoustics, measurement microphone, and omnidirectional sound source.	Iris	T30, T20, EDT, C80, D50, G	T30 1.92 s average in Carthago Nova Theatre. T30 2.25 s average in Saguntum Theatre.
Mexico [37]	Acoustic measurements using impulsive noise were made. A gun generated the noise.	Four measurement condenser microphones and a gun.	Matlab	EDT, T30, T20, C80, and D50	T30 14.45 s at 500 Hz in Mexico City cathedral
Spain [38]	The impulse response was made with sine-swept signals. The frequency range would cover the octave bands from 63 Hz to 16 kHz.	Multipattern condenser microphone. The binaural RIRs were obtained with a Head Acoustics torso simulator.	Easera	EDT, T30, T20, T10, C80, D50, G	T30 0.45 s average in the Theatre. T30 1.3 s average in the amphitheater
Turkey [39]	Acoustic measurements using MLS signals were made.	Omnidirectional sound source, omnidirectional microphone, and handheld analyzer.	Dirac	T30, EDT, C80, D50, STI	T30 between 1.15 s and 1.99 s in the 8 mosques
Italy [40]	Exponential sine sweep with a frequency range from 40 Hz to 20 kHz.	Omnidirectional sound source, binaural dummy head, radiomicrophones.	Mlssa	EDT, T20, C50, C80, D50	T20 1.1 s at 500 Hz in Teatro Nuovo. T20 1.25 s at 500 Hz in Teatro Alighieri
Russia [41]	Impulse responses were measured.	Dodecahedral omnidirectional sound source.	-	C80, EDT, T60	T60 2.18 s at 500 Hz in Rachmaninov Hall
Spain [42]	Exponential sine sweeps were used.	A dodecahedral source, the signal was recorded using 4 microphones and an Ambisonic head.	Aurora	T30, T20, EDT, D50, STI, C80, G	T30 2.25 s average in Palace of Charles V
France [43]	Sine sweeps were used.	Dodecahedron acoustic source, portable recording devices, two omnidirectional microphones, and two autonomous 3D microphones.	Matlab	T20	T20 8 s at 500 Hz (1987). T20 6.8 s at 500 Hz (2015) T20 5 s at 500 Hz (2020) in Cathédrale Notre-Dame
Spain [44]	Sine sweeps were used. The impulse responses were recorded at a sample rate of 48 kHz and 16 bit. Measurements were carried out at night, with the church unoccupied and the background noise was at a minimum.	Dodecahedral sound source, eight microphones.	Easera	EDT, T30	T30 between 9.49 s and 9.8 s at 500 Hz in Cathedral of Cadiz
El Salvador [24]	A balloon was burst to generate impulsive noise.	Portable audio recorder.	REW	Normal modes of the place	-
Italy [45]	Sine sweep signals were used.	Dodecahedron sound source, three monoaural microphones, and a spherical microphone.	Matlab	EDT, T30, C50, C80, G	T30 2.36 s average in Catholic church of Budrio
India [46]	A balloon was burst to generate impulsive noise.	First Order Ambisonic recorder and balloons.	Aurora	EDT, D50, C50, C80, T10, T20, T30	T30 5.145 s average in Cave 3. T30 2.0235 s average in Cave 1. T30 4.7698 s in Cave 11 in Kanheri Caves
Italy [47]	Exponential sine sweep was used as an excitation signal, and the impulse responses. IR were measured.	Dodecahedron sound source, B-Format microphone, dummy head and omnidirectional microphone.	Aurora	T20, T30, C50, C80, D50, Ts, EDT	T30 1.2 s average in Teatro 1763 in Bologna
Egypt [48]	A balloon was burst to generate impulsive noise.	Balloons, portable audio recorder, and omnidirectional microphone.	Dirac	EDT, T20, T30, and T60 C50, and D50.	T20 between 1.238 s and 2.465 s in 19 mosques and T20 6.936 s in Hassan Mosque
Italy [49]	A balloon was burst to generate impulsive noise.	Balloons, microphone.		STI, T30, EDT, C80, and D50	T30 over 2 s at 63 Hz in catacombs of San Gennaro. T30 less than 1 s at all frequencies in catacombs of San Callisto. T30 just over 0.5 s in catacombs of Vigna Cassia
Italy [50]	Exponential sine sweep	One loudspeaker, four eight-channel converter, an audio interface, 25 microphones.	Aurora	T10, T20, T30, EDT, C50, C80, CT, LF, IACC, STI	T30 1.42 s at 500 Hz in Teatro Gall

3.1.2. Rock Art

Table 3 describes the investigations related to rock art studies worldwide. In general, works in this category attempted to identify whether acoustic phenomena influenced ancient cultures to select those specific locations for making their paintings. In particular, Diaz Andreu found evidence that inhabitants painted in places with a high level of reverberant sound since they considered the echo to be magical or extraordinary [51]. Waller concluded that some sites were chosen for rock art due to echo, while others were selected due to sound propagation characteristics, as the inhabitants chose these places since sounds could be heard at great distances [52]. Indeed, areas where murals were often painted were generally identified as places with particular acoustic characteristics, such as long reverberation times.

Table 3. Systems and procedures used in rock art studies identified.

Place	Measurement Information	Registration Hardware System	Measured Parameter	Study Description	Results	Archaeological Type
Caves of La Garma, Las Chimeneas, La Pasiega, El Castillo, and Tito Bustillo. Spain [21]	A sine sweep from 20 Hz to 20 kHz was used. The microphones were separated 1 m from the wall paints.	Portable sound source and omnidirectional condenser microphone.	EDT, T30, C80, D50	Impulse response at specific positions in the cave was captured, where wall paintings (motifs) are. Other measurements in walls without images were taken to compare the information obtained.	Statistical associations between the positioning of motifs and acoustic responses were found in the analyses. The motifs were generally placed where the reverberation is moderate, and there is resonance.	Prehistoric
Rock art landscapes of Baume Brune and Valle d’Ividoro. France/Italy [53]	Air balloons were used for the impact sounds. The microphones were put at a distance greater than 17 m from the reflecting surfaces.	Air balloons, tetrahedral microphone, and audio recorder.	-	Ambisonics technique for capturing the sound was used.	The few painted shelters were those that echolocators would identify as having unique acoustic properties. It is probably that Neolithic artists selected shelters based on some acoustics parameters.	Prehistoric
Canyon lakes of Julma-Ölkky, Somerjärvi and Rotkojärvi. Finland [54]	Sine sweep was used.	Audio recorder, omnidirectional microphones, and omnidirectional sound source.	-	They try to understand more about the soundscape of the place and if any acoustic characteristics were probably considered.	The most pronounced echoes are reflected from the smooth vertical cliffs painted or held as sacred.	Prehistoric
Lascaux cave. France [55]	Concussion idiophone was used.	Class 1 sound level meter.	T60, C50, D50, C80, EDT	Two caves were compared.	The T60 found is high.	Prehistoric
Santa Teresa Canyon. Mexico [56]	Air balloons were used for the generation of impulse response.	Omnidirectional condenser microphone, audio recorder, and air balloons.	G, T20, C50, C80	The sound source was placed at the height of 1.7 m.	Inhabitants were interested in sound. The areas where the murals were painted generally correspond to places with high values of the parameters obtained. Additionally, it is thought that dance was also part of their rituals.	Prehistoric
Sierra de San Serván in Extremadura. Spain [57]	Directional-powered speaker system was at 90.7 dB at 1 m.	Omnidirectional condenser microphone.	Transmission Loss (TL)	The sound source was placed between 130 and 310 m.	Results show that the signal received at rock art sites is louder than at nonrock art shelters.	Prehistoric
Maharashtra. India [46]	Air balloons were used for the generation of impulse response.	Ambisonic recorder, air balloons.	C50, T60, T30, T20, EDT, STI	The recorder was placed far from the walls and the floor. The binaural recorder was set at 48 kHz and 8 bits or 48 kHz and 16 bits.	A total 109 caves were studied, but measurements were made only in three of them. The highest reverberation time was found in cave number 3.	Prehistoric
Lower Chuya River. Russia [58]	They used impulse response signal.	Audio recorder, ambisonics microphone, and dodecahedral speaker.	G, T20, EDT, C50, C80	The distance source–receiver was about 10 m, except on Kalbi-Tash I, for which the distance was 17 m.	Three rock arts were studied. The loudness from a natural amplification of sound could be the reason for the selection of the murals.	Prehistoric
Xaghra Hypogeum, Malta [59]	Clapping, bells, and drum	Two types of dynamic high-end microphones, portable digital recorder	-	The measurements were carried out in two places, the first in a deep well near a stone staircase that leads to the hypogeum and the second in a collapsed cave that overlooks the hypogeum.	The authors concluded that the Xaghra Stone Circle was an important sacred site in ancient times because the vibrations could influence human perception, making their rituals impressive.	Prehistoric

3.1.3. Simulation, Auralization, and Virtualization

Table 4 describes the worldwide investigations on simulation, auralization, and virtualization studies. Many of the studies specified the software used, such as CATT-Acoustic, Odeon, Ease, Comsol, Ramsete, IRIS, Dirac, Google Resonance, and Steam Audio. An article by Llorca-Bofí [60] was identified, where simulations and auralizations were carried out from a photogrammetric model of a room. Similar simulations to those performed with manual 3D models were obtained, so this method could be used in other studies. Additionally, a study by Boren [61] was identified, which aimed to determine whether the staging of speeches given by Julius Caesar in ancient Rome were acoustically plausible. Furthermore, an investigation was identified where the acoustic properties of the musical genre Liederistic were studied through an acoustic simulation using the Ramsete software [62].

Table 4. Systems and procedures used in simulation, auralization, and virtualization studies identified.

Author	Approach	Software	Objective	Results	Archaeological Type
Cathedral of Granada. Spain [63]	Acoustic measurement and 3D model	CATT-Acoustic software	The parameters were simulated and compared with the information obtained from the measurements.	They obtain the predicted acoustic parameters T30, C80, and D50 and how the sounds, especially music (choirs), could be heard in the past.	Historic
Royal Palace of Caserta. Italy [64]	Acoustic measurement and 3D plane	Odeon	The acoustic parameters of the simulated space were obtained.	It was shown that the vaults were usually where the musicians were placed in the rituals.	Historic
Greek and Roman theaters [65]	Simulation	Odeon	The acoustic parameters were simulated, considering that people entirely occupied the theater.	They identify through simulation that there is a decrease in energy, especially in low frequencies because of the audience in the cavea of the theaters.	Historic
Laboratory simulation [66]	Simulation	Odeon and CATT-Acoustic software	A comparison of the simulations obtained using Odeon and CATT-Acoustic software.	They concluded that Odeon is more sensitive to variation in sound absorption than CATT-Acoustic software.	-
Las Pailas. Argentina [67]	Acoustic measurement and 3D model	Comsol	Analysis of how architecture could affect sound dispersion in public places within ancient settlements.	They were able to identify the possible places where people were located around the archaeological place, to be able to see and hear what was happening properly; they consider this investigation as a preliminary study that is limited by the lack of information such as the height of the walls.	Prehistoric
Hypostyle mosque of Cordoba. Spain [68]	Auralization, simulation, and 3D of the area	CATT-Acoustic software	A 3D model of the area was developed to obtain similar acoustic parameters between the measurements and the simulation.	Different constructive configurations of the mosque were simulated, obtaining different acoustic characteristics and auralizations of the place in the past.	Historic
Rostra and the podium of the Castores Temple in Rome. Italy [69]	Simulation	CATT-Acoustic software	Estimation of the number of Romans who could have heard the speaker clearly.	They indicated that around 300 people could understand the discourse in this place.	Prehistoric
St. John Baptistery in Pisa. Italy [70]	Simulation	-	Comprehension of the acoustic phenomena of the place.	After the simulations, a T60 higher than 10 s within this place was found.	Historic
Gothic Vadstena abbey church. Sweden [71]	Simulation and a 3D model	Odeon	A 3D model of a church was produced to investigate the sound propagation of that church in 1470.	The authors concluded that there were spaces with acoustic differences, such as the place used by the nuns that has a shorter EDT, a major G, and an improved C80, compared to the rest of the church.	Historic
Church of San Luis de Los Franceses. Spain [72]	Acoustic analysis of the church and simulation	CATT-Acoustic software	They considered different uses, occupations, and sound sources to investigate how the place has changed acoustically over time from 18th to 21st century.	The changes over time have not been significant, this is since there have not been such important variations in its construction characteristics, although some coatings have been modified, the changes have been minor, keeping the acoustics similar.	Historic
Cathedral of Saint Albert Puglia. Italy [19]	Acoustic simulation and 3D model	Odeon and Ease software	An acoustic simulation of the space cathedral of Saint Albert in the archaeological site Montecorvino.	VR simulation was made, and a binaural playback system where users listened to some medieval music.	Historic
Cathedral of Saint Albert Puglia. Italy [73]	Acoustic simulation and 3D model	Odeon and Ease software	An acoustic simulation of the space cathedral of Saint Albert in the archaeological site Montecorvino.	It describes in detail the information related to the acoustics procedure of paper [19].	Historic
Hall of St. Cecilia, a concert hall. Scotland [74]	Compared different auralization methods	Google Resonance and Steam Audio	They recreated the place and made a 3D model in actual conditions and a recreation of the site in 1769.	They found that the listeners qualified better 1769 acoustic characterization of the place.	Historic
14th-century church of the Jeromite monastery of Santa Maria de la Murta. Spain [75]	Virtual acoustic reconstruction, simulation, and auralization	CATT-Acoustic software	They tried to detail the history of la Murta (a church in ruins) through acoustic reconstruction and auralization. It was virtually reconstructed to have an idea of its environmental condition.	They made a virtual reconstruction of the church using the ruins and archives. They validated the acoustics with a similar existing church such as Sant Miquel dels Reis, or El Escorial, obtaining only approximate results.	Historic
Lazarica Church. Serbia [76]	Acoustic measurements and simulation	Ease software	The aim was to learn more about the traditions and practices carried out inside the church, focused mainly on acoustics.	They verified that the decay of the sound energy was uniform for the whole place. It was performed using the parameters T30 and EDT.	Historic
Thomaskirche church. Germany [77]	Acoustic measurements and simulation	CATT-Acoustic software	They made a simulation of the church in two historical moments: in the time of J.S. Bach in 1723 and the time of the Lutheran church in 1539.	The T60 in the simulation of the empty church in 1723 has less than in the simulation of 1539. In 1723, there were more galleries that reduced the T60. The T60 was similar in the two simulations when they were full of people.	Historic
The Alighieri Theatre. Italy [78]	Acoustic measurements and simulation	Odeon	They made a comparison with and without the proscenium of a Historical Opera House.	The proscenium helped to highlight the sound of the voice, although it is misleading in terms of clarity.	Historic
Palais du Trocadero. France [79]	Simulation	CATT-Acoustic software	The objective was to conduct simulations to determine if the absorbent material improved the acoustic conditions of the concert hall.	This paper concluded that the architects who built the place ignored the reflection that produces echo, and that the absorbent material placed later does not solve this problem.	Historic
Cistercian Beaulieu Abbey. United Kingdom [80]	Acoustic measurement and recreation of the place	CATT-Acoustic software	The objective was to recreate acoustically the destroyed Cistercian Beaulieu Abbey.	They concluded that there were good intelligibility conditions from the altar to the Abbey but very poor towards the central nave.	Historic
Bell Church in Cappadocia. Turkey [81]	Measurement, simulation, and auralization	Odeon	They made tests with an impedance tube to determine the absorption of the materials and recreate the place.	The sound coefficients of absorption demonstrated that the tuff stones were very reflective. Researchers concluded that the clarity of the place might not be clear for liturgical events.	Historic
The Roman amphitheater located in Santa Maria Capua. Italy [82]	Measurement, simulation and 3D model	Odeon	The objective was to make a 3D model of the place for calibrating the absorption coefficients to restore its original activity: that is, the presentation of shows.	The acoustic simulation showed more balanced responses from the place than the measurements.	Historic
The Roman theater of Verona. Italy [83]	Measurement, simulation and 3D model	Ramsete	The objective was to carry out a reconstruction of the open-air theater through a 3D model.	The acoustic conditions of the theater diminished because of the absence of some elements, such as the upper gallery.	Historic
Cathedral and Metropolitical Church of St Peter. United Kingdom [84]	Measurement, simulation and 3D model	WinMLS2004 and IRIS	The objective was to evaluate the acoustics of the Chapter House of the Cathedral.	The results show that the design gives priority to the visual, but not to the acoustic due to the high reverberation that causes speech intelligibility problems.	Historic
The Roman theater in Malaga. Spain [85]	Measurement, simulation and 3D model	Odeon	The aim was to investigate the acoustic effects that produced the closeness of the Muslim Alcazaba and the hillside over the Roman theater.	The results show that there is an influence of the hill and the large stone that is near the theater on the time decay parameters.	Historic
Hagia Sophia and Süleymaniye Mosque. Turkey [86]	Measurement and simulation	Odeon	The aim was to investigate the effects of architecture, construction material attributes, and applied alterations in basic restoration works.	The principal difference between the two structures is that Hagia Sophia was designed as a church, and Süleymaniye is a mosque, which means that the acoustic characteristics are very different between them.	Historic
Cathédrale Notre-Dame, París Francia [87]	Simulation with scale models	Matlab	The study investigates the sound in seven relevant designs and the architectural style itself.	It was found that small geometrical features produce diffuse reflections similar to surface diffusers. There are also low-level resonances due to complex forms that are a small part of the total energy; also, great spectral differences between piers were observed.	Historic
Four churches in Spain [88]	Measurement and simulation	Easera with Aubion	This study develops the acoustic evolution of the choir in cathedrals in Spain.	The choir is reserved for the clergy; therefore, it has an acoustic influence in the cathedrals space.	Historic
Roman theater of Posillipo. Italy [89]	Measurement and 3D model	Odeon	The research aim was to reconstruct the theater acoustically as it sounded in the Imperial period.	Currently, the theater presents good conditions for understanding speech. With the simulation of the past, they confirmed that the acoustic characteristics should be favorable for speech.	Prehistoric
Cassino, Taormina, Pompeii and Benevento. Italy [90]	Measurement and virtual model	Dirac and Oden software	The investigation aim was to determine the acoustics effects of the audience on ancient theaters.	The simulations show that the geometry of the theater and the area occupied is important for getting better acoustical results.	Historic
Five ancient Roman theaters. Italy [91]	Measurement and virtual simulation	Dirac and Oden software	This study compares the acoustics characteristics of five theaters, considering their architecture and the materials used in their restorations.	The results show some insufficient acoustic characteristics, and values of the reverberation time that do not exceed 1 s. Additionally, the results show that the absence of reflective surfaces makes the acoustics into a challenge.	Historic
Theatre of Syracusae, Italy [92]	Measurement and simulation	Odeon	The study aims were to investigate which parameters could be considered the better for the design of new scenarios.	Due to the use of the ISO 3382-1:2009 standard, the evaluation of the best acoustic parameters for the implementation of simulations of models of open places is complicated.	Prehistoric
Cathedral of Seville. Spain [93]	Measurement and simulation	CATT-Acoustic software	This study evaluates the acoustic of the cathedral, considering different configurations used for concerts and other ceremonies.	The massive attendance of people improves the acoustic conditions of the cathedral for concerts. Nevertheless, with the use of new materials, the acoustic could be improved.	Historic
Cathedral of Seville. Spain [94]	Virtual 3D models and auralization	WinMLS2004 and CATT-Acoustic software	The paper presents the VR results in the Cathedral of Seville and describes the processes of creation and calibration of a 3D model.	The perception was validated with a questionnaire that showed that the Cathedral of Seville was acceptable for choral singing and music. Still, it had the problem that it is reverberant for word transmission.	Historic
The Bayreuth Festspielhaus theater, Germany [95]	Measurement, simulation, and virtual experience	Odeon	This research aimed to determine the role of the BF theater through acoustic measurements and then develop an immersive virtual experience.	In the BF, all acoustic and visual conditions are almost the same in the whole theater.	Historic
Cathedral of Notre-Dame, France [96]	Measurement and simulation	CATT-Acoustic software	The aim of the research was to recreate the cathedral of the 12th and 13th centuries and to understand the relationship that existed between the occupants and the acoustic characteristics of the place.	The results show an acoustic evolution occurred between 1163 and 1220.	Historic
Cathedral of Notre-Dame, France [97]	Measurement and simulation	CATT-Acoustic software	The aim was to study the modifications presented in the transept and side chapels of the Notre-Dame Cathedral.	The changes in terms of T30 and EDT considering the modifications in the transept and chapels were small.	Historic
Berlin Konzerthaus, Lviv Opera House, Germany and Teatro del Maggio Musicale in Florence, Italy [98]	3D modeling, auralization, and virtualization	-	The objective of the research was to develop three different approaches to the theater halls for realizing 3D, auralization, and immersive virtualization of the selected places.	The methodology used allowed modeling and rendering as a means of protecting and preserving a virtual memory of places.	Historic
Miners’ Theatre in Idrija, Slovenia [99]	Measurement and simulation	Ramsete	The purpose of the investigation was to recreate the place in its original form and simulate the measurements with and without people.	The results show that the place was propitious for oral presentations but inappropriate for musical presentations.	Historic
Benevento Roman Theatre, Italy [100]	Measurement and simulation	-	The objective was to evaluate the acoustic characteristics to understand the optimal types of theatrical performances that could be performed.	The theater lacks reflective surfaces that provide good acoustics for musical performance.	Historic
Church of San Dominic of Foligno and San Dominic of Imola, Italy [101]	Measurement and simulation	Ramsete	The objective was to highlight the importance of using acoustic simulations in historical places to improve the sound inside them.	S. Dominic church of Imola is more reverberant than S. Dominic of Foligno, and there is a big difference between the two churches in the parameters C80 and D50.	Historic
Tindari Theatre, Italy. Notre-Dame de Paris Cathedral, France. The Houses of Parliament, United Kingdom [102]	Simulation and auralization	-	The objective of the project was to create a prototype that allows the conservation of historical sites in very poor condition so that it can be used by museums or interested persons.	The software was developed to combine documentation processes with acoustic simulations of historical places and thus preserve the places.	Historic
Roman theater of Gortyna, Greek [103]	3D model, simulation	Odeon	The objective of the investigation was to determine what uses the theater could have had.	According to the acoustics of the theater, it was shown that it could have been used to give talks and performances since the spoken word is heard easily and clearly.	Historic
20 Ancient Greek Theatres, Greek [104]	Simulation	CATT-Acoustic software, Odeon	The aim was to demonstrate the acoustic importance of the scenery for the people’s comfort in the ancient Italian theaters	Putting up a removable scenery could help protect ancient theatrical monuments.	Historic
Roman theater of Cadiz, Spain [105]	3D model, simulation	CATT-Acoustic software	The purpose of the paper was to build a 3D model and the simulation of the places where the excavations were carried out, which are the cavea, the proedria, the orchestra place, and an annular gallery.	The results show that the theater is highly reverberant due to its large dimensions and the stone finish despite being semiopen.	Historic
Theater Odeon of Pompeii, Italy [106]	Measurement and simulation	Dirac	The article analyzes the current acoustic characteristics of the Odeon to reconstruct virtually and present suggestions for its future use.	The building in its current state is suitable for spoken performances while adding a wooden roof could be suited to musical performances.	Historic
Andalusian cathedrals, Seville, Granada, Jaen, Malaga, Cadiz, Cordoba Spain [107]	Measurement and simulation	WinMLS2004	This paper aims to preserve the sound of the cathedrals through simulations.	The authors concluded that cathedrals have a reverberation time above those considered acoustically appropriate for transmitting words and music.	Historic
Carsı Mosque, Turkey [108]	Measurement and simulation	Odeon	The objective of the investigation was to the change suffered by the acoustic parameters related to the materials and density of the walls, as well as the people who are in the place.	The results showed that if the place is full of people and the type of surface is changed, the acoustic parameters of the site change, especially in relation to low frequencies.	Historic
San Domenico of Imola, Italy [109]	Measurement and simulation	Ramsete	The purpose of the investigation was to determine if it is possible to turn the Domenico of Imola church into a place to listen to music.	The authors determined that converting the church into a temporary auditorium for listening to music was complicated since it did not have an appropriate acoustic design. Still, they gave suggestions to reduce external noise.	Historic
The Odea of Pompeii and Posillipo, Italy [110]	Measurement and simulation	Odeon	The purpose of the article was to study the acoustic characteristics of two Odeons (covered buildings), the largest located in Pompeii and the smallest in Posillipo, Naples.	The results showed that the Odeon of Pompeii, which is the largest, is appropriate for music and that of Posillipo was appropriate for speech.	Both
Cathedral of Benevento, Italy [111]	Measurement and simulation	Odeon	The objective of this work was to carry out acoustic measurements of the church and then test ceramic materials to correct the acoustics of the place.	It was determined that the use of ceramic material and microperforated sheets could perform a good acoustic correction.	Historic
Chaco Canyon, United States [112]	3D Model, simulation	Soundshed Analysis Tool (authors development)	The research sought to conduct an acoustic simulation of the archaeological site to gain a better understanding of the soundscape of the area.	The mounds were constructed in a specific location to serve as a stage for political theater, that everyone could see around the Downtown Chaco.	Prehistoric
Eszterháza Opera House, Hungary [113]	3D Model, simulation	Ramsete	This study aimed to obtain the original acoustic characteristics of the place when it was first built. To do this, the study was based on historical information.	The reverberation time is favorable for both music and speech transmission. The audience presence had little impact on the acoustics of the theater.	Historic

3.2. Musical Instruments and Pieces

Table 5 summarizes the worldwide research on studies of musical instruments and pieces. The most studied instruments include turtle shells, bullroarers, aerophones, notched idiophones, and wind instruments.

Table 5. Systems and procedures used in musical instruments and pieces studies identified.

Place	Instrument	Objective	Results	Archaeological Type
United States [114]	Turtle shells with holes	It was analyzed in different ways if the holes made in the tortoiseshell were produced by humans with some specific use, for example, to make music.	It has not been fully established that they were built to generate music, but they were likely used for that purpose.	Prehistoric
Africa [115]	Instruments called bullroarers	Replicas of these instruments were made and recorded to find their acoustic characteristics.	They indicated that it is essential to carry out more studies to understand the cultural contexts in which musical instruments were used.	Prehistoric
Africa [116]	Bullroarers	Recreation of bullroarers to identify the acoustic characterization.	The characterizations of different bullroarers were obtained and demonstrated that they could be used to produce different musical sounds.	Prehistoric
Belize and Guatemala [117]	Wind instruments	Based on photographs of existing musical instruments found in Belize and Guatemala, they made a 3D impression of them. Then, they recorded the 3D instruments to obtain their sound characteristics.	The results show similarities in physical characteristics compared with the photographs of the original instrument. Nevertheless, they could not evaluate the sounds with the original.	Prehistoric
Campeche, Mexico, and Copán in Honduras [118]	Wind instruments	This investigation carried out an acoustic characterization of wind instruments in Campeche and Copán.	The acoustic characterizations of wind instruments such as flutes were carried out in Campeche and Copán.	Prehistoric
Campeche, Mexico [22]	Aerophones	This investigation carried out an acoustic characterization of aerophones in Campeche.	Several wind instruments with different sound characteristics were studied.
State of Mexico [119]	Notched idiophones	This investigation carried out an acoustic characterization of notched idiophones in the state of Mexico.	Acoustic characterizations of notched idiophones were carried out. The use of skulls placed under these idiophones to generate sound amplification was studied.	Prehistoric
Teotihuacan, Mexico [120]	Horns, trumpets, and pipes	This research studied the acoustics of wind instruments in Teotihuacan.	The fragmented state of the artifacts presented needed reconstruction to obtain the original sounds.	Prehistoric
Teotihuacan, Mexico [121]	Quadruple flutes	This study created a 3D model of quadruple flute in Teotihuacan.	The authors made a 3D impression of the upper part of one of the quadruple flutes to understand the operation of this flute better. However, they do not present an associated acoustic analysis.	Prehistoric
China [122]	The qin is a seven-string zither	The objective is to explore the few acoustic studies carried out on the Chinese instrument qin.	The fundamental frequencies of the qin strings are lower than the sound box.	Prehistoric
Sudan [123]	Rock gongs	This study analyzes the acoustic properties of rock gongs in relation to the surrounding landscape.	The investigation confirms that the rock gongs could produce sustained musical sounds.	Prehistoric

4. Discussion

This work reviews recent investigations in the field of Archaeoacoustics from 2016 to 2022. One-hundred and five papers were selected and divided into two categories: (1) Archaeoacoustics in places and (2) Archaeoacoustics of musical instruments and pieces. Ninety-four papers were classified under the first category, and eleven under the second. The first category was further divided into three subtopics: (1) measurement and sound characterization of sites (28 papers), (2) rock art (11 papers), and (3) simulation, auralization, and virtualization of places (55 papers). According to the information obtained, it was identified that in measurement and characterization studies, six papers (27%) were categorized as prehistoric and sixteen papers (73%) as historic. All rock art studies (eleven papers) were prehistoric, while six papers (12%) of simulation, auralization, and virtualization studies were prehistoric, and forty-six papers (88%) were historic. All studies of musical instruments and pieces (eleven papers) were prehistoric.

4.1. Recent Advances

4.1.1. Measurement and Characterization

The research objective of these studies was to measure the acoustics of a particular place and evaluate the key parameters that affect sound propagation. Acoustic characterization is fundamental to comprehend the sound propagation behavior of a place.

In general, researchers of pre-Hispanic zones attempted to understand if inhabitants in those places considered acoustics when constructing their buildings. Authors proposed that these places could have been used for rituals, mass events, and religious events.

Some other authors sought to characterize more recent places to investigate the acoustic behavior of those sites and how they have changed over time. An example of this investigation is the work conducted in the Acheiropoietos Basilica and the Cathedral of Hagia Sophia in Greece, where authors aimed to explore the choral songs related to the acoustic conditions of the place [34]. Other examples are the research undertaken by Till [35] and Astolfi [36], who acoustically characterized the Paphos Theater in Cyprus, and the theater of Tyndaris in Italy, respectively. They studied the acoustic characteristics of ancient open-air theaters and the use given to these places. Girón investigated the acoustics of two Roman theaters in the Cartaginensis province of Hispania, Spain [20]. In [38], the authors performed the characterization of the Roman theatre in Spain, which has the best-preserved cavea in Hispania and the amphitheater with its southern restored cavea. Study [39] developed the measurements at eight mosques in Turkey. Additionally, there is the case of an investigation in Mexico, where the acoustic characterization of the Cathedral of Mexico City was carried out [37]. Finally, an interesting work to point out is that conducted by Cox, who used a scale model of the Stonehenge ruins to obtain configurations as those presented in ancient times. In this case, the stones could be relocated to analyze different acoustic scenarios [23].

In terms of measurement quality, it is essential to emphasize that several works [20,23,34,35,36,38,39,40,41,42,43,44,45,46] were conducted in accordance with the ISO 3382-1:2009 standard, ensuring that results could be reproduced or compared eventually. Moreover, almost all the studies that characterized spaces used loudspeakers as a sound source, with the exception of [37] that used a gun and [24,46] that used balloons. Astolfi also used a second sound source: a firecracker blast [36]. Most of these studies employed measurement microphones, with the exception of [26]. Some studies also utilized portable recorders. Most of the authors calculated acoustic parameters related to the reverberation time, such as T₂₀, T₃₀, EDT, and T₆₀. In [33,36,37,38,39,42,46], parameters C_50, C₈₀, D₅₀, and ALcons were included. Additionally, the authors in [26] reported the power spectrum and level attenuation using different sound sources, and [24] obtained the normal modes of their studied site. Regarding the reverberation time, Table 2 presents information on the values obtained in various investigations. It can be observed that these values vary greatly, which is understandable as the studies were conducted in different places such as cathedrals, open and closed theaters, churches, etc. This results in values ranging from as low as 0.5 s to as high as 15 s.

4.1.2. Rock Art

In rock art studies, researchers generally aimed to determine whether the locations chosen for the paintings corresponded to areas with long reverberation times [21,54,57]. They also investigated whether the inhabitants had any prior knowledge of the acoustic properties of the location [51,52,55]. For example, Fazenda explored five caves in Spain and found that murals were painted in areas with moderate reverberation and low frequency resonances [21]. Mattioli analyzed murals painted in shelter areas in France and Italy and used Ambisonics techniques to record sounds. They found that the shelters had a long reverberation time [53]. Rainio studied three rock cliffs in northern Finland, where large-scale murals with various shapes, such as people playing drums, were found. Those rock cliffs presented a high level of reverberant sound, as well. One of the cliffs even generated a phantom sound source, simulating that the sound came from the paintings [54]. Diaz-Andreu investigated murals in Spain, Italy, and France and proposed that the Neolithic artists who painted them had some understanding of acoustics [51]. Waller hypothesized that some ancient paintings served ritual purposes and were painted in caves with strong echoes, simulating that the paintings spoke. They tested this hypothesis by examining several caves, including Horseshoe Canyon, the Cave of Niaux, and the Cave of Cougnac [52]. Commins analyzed the Lascaux cave, where large bull paintings were found. They found significant echoes in the areas where the paintings were made [55]. A method for measuring the acoustic properties of the Sierra de San Serván area in Extremadura (Spain) was proposed in [57]. The authors used transmission loss (TL) analysis to determine the audibility of distant sounds and concluded that prehistoric artists believed that sounds went beyond their paintings. In Mexico, Díaz-Andreu showed that ancient artists selected the best sonic landscapes to paint their murals in Baja California Sur [56]. In [46], the authors acoustically analyzed three caves out of the 12 Kanheri Caves located in India and found that one of them had high levels of reverberant sound, around 5.145 s. In [58], the authors reported that murals in the Lower Chuya River were located in places where sound is amplified, and music and speech are clearly diffused.

To carry out the acoustic characterization, some works, including [21,46,53,58], followed the ISO 3382-1:2009 standard. Some authors such as [21,54] used frequency sweeps, while others, such as [46,53,55,56,58], generated impulsive noise. Works including [46,53,56] used air balloons, and in [55], concussion idiophones were preferred. The most relevant findings of the selected literature are described in Table 3.

4.1.3. Simulation, Auralization, and Virtualization

Works encompassed under this topic include: (1) simulations of various historical sites [63,64,65,66,67,68,69,70,72,76,77,78,79,80,81,86,87,88,92,93] and (2) virtual reality and auralization models of the studied areas [19,71,73,74,75,82,83,84,85,89,90,91,94,95]. The most relevant studies are described as follows:

Alonso performed a 3D simulation of the Cathedral of Granada in Spain to study its acoustic characterization over three different historical periods [63]. Alberdi carried out a similar investigation in Church San Luis de Los Franceses in Spain, where, using acoustic simulations, they studied the church changes throughout history [72]. Acoustic simulations were also performed at the Royal Palace of Caserta in Italy to study the spatial distribution [64]. D’Orazio performed an acoustic simulation of St. John Baptistery in Italy to understand its historical evolution [70]. Suarez made an acoustic simulation of the Islamic temple Aljama Mosque of Cordoba in Spain to obtain different constructive configurations of the past of this temple to reconstruct the historical sound [68]. Sender presented the virtual and acoustic reconstruction of the 14th-century church of the Jeromite monastery of Santa Maria de la Murta in Alzira. This work studies the acoustic evolution of the existing church in comparison with a reconstruction of the destroyed or poorly conserved rooms [75].

In [79], the acoustics of the Palais du Trocadero (1878–1937) were studied through simulations. Those simulations were based on the theory of sound perception and reflections of the first order. However, their method produced many echoes. In 1909, they tried to correct this problem by placing absorbent material, which did not work as expected. The conclusion was that the reflections were reduced using absorbent materials, but a total solution to the problem was not achieved due to surface forms.

In [77], the prediction of Bagenal was studied. This established that the Thomaskirche church had a shorter reverberation in Bach’s time from 1723 to 1750 than in the 16th century, as a result of the Lutheran alterations. They concluded that when the church in 1723 was empty, it had a lower T₃₀ value than today. In contrast, the church in 1539 was more reverberant than today, but when the church had the presence of people, the T₃₀ was less significant. In [81], researchers developed a simulation of the Bell Church to archive the best results from possible constructive materials. The absorption coefficient was acquired using an impedance tube to achieve a similar simulation to the original place. In [78], the authors studied the proscenium of The Alighieri Theatre in Ravenna. They concluded that the proscenium increased the sound force of the soloists, but the intelligibility was reduced. In [67], the authors developed a simulation in the archaeological site named Las Pailas in Argentina to determine the best places to see and hear correctly around the place.

Additionally, Iannace carried out acoustic simulations of the theaters Taormina, Pompeii, and Benevento in Italy to estimate their acoustic features, considering that they were crowded with people. They concluded that acoustics change according to the geometry of the theater and it is influenced by the audience [65]. In [76], researchers developed the simulation of the Lazarica Church to study the acoustic and construction traditions of the place. The study of Kopij was carried out in the Roman Forum, Italy. Initially, they sought to identify the best areas for holding conferences. Once those points were determined, they conducted acoustic simulations of the place to know the approximate number of people who would simultaneously listen to a meeting or event [69]. Duran also developed a simulation of Beaulieu Abbey. They found that it was constructed for promoting sacral music rather than intelligibility [80].

On the other hand, Bo performed simulations of the Syracuse theater in Italy to compare the accuracy of the Odeon and CATT-Acoustic software [66]. Selfridge sought to identify the effectiveness of two audio plugins used in audio spatialization in immersive virtual environments: (1) Google Resonance, and (2) Steam Audio. For this purpose, they did an acoustic simulation of the Hall of St Cecilia in Scotland. They tested two architectonical configurations: one of 1769 and the other of 2018 [74]. Additionally, they performed two different auralizations of sounds. They finally performed a subjective evaluation with participants to determine if they listened differently to these two auralizations. They found that most participants could distinguish between them. Autio undertook a similar investigation. They performed an auralization of Vadstena abbey church in Sweden, as it was in 1470 [71]. In [82,83], the authors developed 3D models of the cathedral of Saint Albert to make a virtual representation of the place to recreate the site using immersive techniques. Grazioli and Rumsey carried out an interactive virtual reality experience of the cathedral of Saint Albert, Italy. They first created a 3D model of the area since the church is currently in ruins. They acoustically characterized the place and auralized the sounds. Later, participants were exposed to the auralized sounds in a virtual reality model to evaluate the degree of sound presence [19,73].

4.1.4. Musical Instruments and Pieces

In the study conducted by Katz, a 3D printer was used to recreate a flute from the Mayan culture located in a Guatemalan museum. The replica was made using photogrammetry techniques [117]. Gillreath-Brown recreated turtle shell rattles found in the United States to prove that these shells were used as musical instruments [114]. Kumbani and Rusch attempted to prove if the bullroarers found in Africa were used as musical instruments, specifically as an aerophone [115,116]. In Latin America, investigators have opted for the characterization of musical instruments into acoustically conditioned cameras. Some of the most relevant studies have been (1) Mayan triple flutes from the archaeological sites of Jaina in Mexico and Copan in Honduras [118], (2) notched idiophones from Teotenango in Mexico [119], (3) aerophones from Calakmul in Mexico [22], (4) horns, trumpets, and pipes [120], and quadruple flutes [121] both in Teotihuacan Mexico.

4.2. Overview of the Main Contributions

4.2.1. Measurement and Characterization

Nowadays, there has been significant progress in simulation, virtualization, and auralization, which enable modifications of materials [74] or constructive features [63,72]. In many instances, this technology can even bring a closer replication of the original sound environment. Auralization and evaluation of sound perception within the environment are also possible. Note that it has been essential to consider the ISO 3382-1:2009 standard to ensure the validity, reproducibility, and comparability of the results obtained.

It is believed that ancient inhabitants had a basic understanding of acoustics and built their structures taking into account the sound properties of the environment, particularly for adding mysticism to religious ceremonies or events. One notable study in this area was the recreation of Stonehenge by Cox. However, this type of model reproduction is only feasible for smaller structures, such as Stonehenge, and not for larger structures such as the pyramids in Mexico, where the size and number of buildings make replication difficult [23].

4.2.2. Rock Art

There is no established methodology for conducting acoustic measurements in relation to rock art. However, new techniques, such as Ambisonics for sound recording, have been incorporated. Previous studies have emphasized the importance of adhering to the ISO 3382-1:2009 standard and using loudspeakers to enhance measurement accuracy.

In general, it is believed that the ancient inhabitants had some notion of acoustics and chose to paint murals in areas with high levels of reverberant sound, including echoes [16,17], to add mysticism to religious or social events.

4.2.3. Simulation, Auralization, and Virtualization

The approach in [63,72,74,77] is interesting since it allows the comparison of acoustic characteristics over time in an area, considering the constructive changes. Acoustic simulations are valuable and could be used to study sound behavior in archaeological sites.

Simulations can be used to spatially identify sound behavior in a room under specific conditions, which is a fascinating approximation, as seen in studies [64,65,68,70,72,75,76,77,80,81,83]. By simulations, the degree of intelligibility of an area could be established, making it possible to define the purpose of different spaces in the past (e.g., social events or conference rooms) [69].

The use of acoustic simulation software such as Odeon and CATT-Acoustic has increased in recent years. For example, Selfridge used auralization techniques to create a virtual acoustical place, which was acoustically evaluated by participants [74]. Autio also presented auralizations of the site; however, these auralizations were not shown to participants [71]. Grazioli and Rumsey went a step further and designed both the 3D model and auralization of the place. It is valuable to note that they also conducted evaluations for participants based on an informal survey. They reported that most participants reported an immersive experience [19,73]. It is also interesting to note the research by Adeeb [81], which proposed using an impedance tube to obtain acoustic characteristics of materials to develop the simulations.

4.2.4. Musical Instruments and Pieces

There is significant evidence of the use of different components (e.g., turtle shells, bullroarers, rocks, bones, etc.) and elements of nature that allowed the inhabitants of several cultures to make musical instruments [22,114,115,116,118,119]. This confirmed that sound has been essential in human life.

As an illustration, Zalaquett recorded musical instruments in a semianechoic room, to obtain their acoustic characteristics. This approach could be applied to estimate the acoustic parameters of other musical instruments around the world (e.g., flutes, notched instruments, and percussion instruments) [22,118,119].

The research conducted by [117] is fascinating since it used photogrammetry techniques to simulate a musical instrument, which could be applied in other areas, for instance, to recreate an entire archaeological zone.

5. Conclusions

After the review, two main topics were identified: acoustics in archaeological places and acoustics in musical instruments and pieces. The first topic accounted for 89.5% of the articles and was divided into three subtopics: (1) measurements and characterizations at 26.6%, (2) rock art at 10.5%, and (3) simulation, auralization, and virtualization at 52.4%. The topic of musical instruments accounted for 10.5% of the articles.

Regarding the measurement and characterization studies, it was found that the articles mostly used the ISO 3382-1:2009 standard related to measuring acoustic parameters in rooms. However, there is currently no standard for open spaces; so, the ISO 3382-1:2009 is often used in these cases. Additionally, it is feasible to identify the best acoustic parameters to characterize open-air archaeological sites, as proposed in [36].

Furthermore, it is essential to determine an adequate number of recording points to achieve accurate measurements in different archaeological sites, as stated in [35]. Additionally, replicas of different archaeological sites should be constructed to test different configurations and obtain multiple acoustic characterizations, as done in [23]. Many investigations in this field also include simulations of the areas being measured.

Despite the aforementioned points, the ISO 3382-1:2009 standard has been used in open spaces. This raises the need to develop more specific methodologies for these cases [20,33,34,37], such as theories of sound propagation outdoors [124]. Additionally, it is required to identify other acoustic parameters [36].

In the case of rock art, many authors concluded that the places where the murals were painted had some acoustic behavior. Although, it cannot be proven in all cases that the painters understood acoustics, it seems very likely that they had certain considerations, even sacred, for choosing those sites. Some researchers have used air balloons to obtain the impulse response for measuring these places. In this subtopic, the investigations that used ISO 3382-1:2009 standard were minimal.

It would be interesting to acoustically characterize other caves with painted murals to compare them to previous studies [21,51,52,53,54,55]. Virtualizing these caves with new technologies could be an interesting approach to recreate the sounds and places. Establishing a methodology for measuring rock art would be desirable to ensure that all investigations meet the same standards.

The area related to simulation, auralization, and virtualization is currently growing and developing, mainly due to the advancement of computational capabilities (e.g., CATT-Acoustic, Odeon, Ease, Ramsete, etc.), which allows more options in the field of simulation and recreation of spaces. On the other hand, for the studies related to rock art and musical instruments, we identified the fewest number of investigations, making these areas an opportunity for further research. The relevance of these types of studies lies in gaining a better understanding of past cultures.

Measurements only provide the current acoustic characteristics of the buildings, not the original acoustic characteristics that the buildings had with their original materials. Therefore, using methods such as the impedance tube, as used by Adeeb [81], to obtain the original materials’ acoustic characteristics enables simulations that are closer to the original acoustic characteristics of the buildings, enabling virtual recreation of environments that are as authentic as possible.

In this subtopic, the norm ISO 3382-1:2009 is only applicable when the first step is to make measurements of the original place.

It would be possible to create 3D models that allow acoustic simulations of different archaeological sites, as proposed in [33,37]. In archaeological zones, acoustic evaluations could be conducted inside buildings, as seen in [26]. With the advancement of new technologies, it could be interesting to virtually recreate spaces and make auralizations to generate virtual scenarios similar to real ones to better understand the acoustic behavior of archaeological sites [63,64,65,72]. Furthermore, it is necessary to establish the number of points required to perform auralizations that allow participants to move freely through an area of interest [74].

Finally, it could be interesting to conduct auralizations of different sounds in archaeological zones to evaluate sound perception using both quantitative and qualitative methods, building upon previous work [19,73]. All of this could be enhanced by utilizing neuroscience to evaluate the participants’ experience by measuring their response to a virtual acoustic environment.

In the subtopic of musical instruments and pieces, these investigations seek to characterize the studied musical instruments acoustically. Although there is no single methodology, different authors present different approaches, such as the use of the photogrammetry technique used by Katz to make a model of the instrument and then obtain its acoustic characteristics, even though these will not be exactly the same as the original due to the materials used for their manufacture [117]. The research done by Katz could be extrapolated to create 3D models of complete archaeological sites for simulating virtual acoustic spaces [117]. However, the ISO 3382-1:2009 norm is not applicable for musical instruments and pieces studies.

Within the studies of musical instruments, there is a methodological approach developed by Zalaquett to characterize musical instruments, it could be desirable to replicate this methodology to characterize other musical instruments in different archaeological sites [22,118,119] to deepen and generalize its use. Finally, it could be interesting to study the use of bones and rocks as musical instruments, such as the notched idiophones investigated by [22,118,119] and rock gongs by [123].