## Preface The word [[Acoustics]] is originated from the Greek word _akouein_ (ἀκούειν), and Joseph Sauveur coined the term _acoustics_ for this science of sound he pioneered in 1701 [1]. ## Introduction Archaeoacoustics, also known as Auditory Archaeology, is an emerging interdisciplinary field that combines archaeology and acoustics. It focuses on studying archaeological spaces by examining their acoustic properties and characteristics. [2][3][4] According to Navas-Reascos et al., Archaeoacoustics has had a wide variety of study aims, including socio-political studies to obtain information among different cultures. ## Acoustical analysis procedures of Archaeoacoustics The acoustical analysis procedures of Archaeoacoustics researches have been standardized to ensure similar quality characterizations of archaeological spaces [5][6]. ### Reverberation time $T_{60}$ Reverberation time $T_{60}$ is regarded as the most basic and important objective parameter of the Acoustics study, which can be used to measure how long a sound remains after the sound source is turned off. It was first proposed by W. C. Sabine (1868-1919), and it marked the beginning of modern room acoustics. It is measured in seconds and is obtained when the sound energy reduces by 60 $\text{dB}$. Sabine's formula is: $$T_{60} = 0.161 \frac{V}{A}$$ where $V$ represents the analyzed room volume (in cubic meters), and $A$ denotes the equivalent absorption surface of the room (in square meters). ### Sound pressure level (SPL) The sound pressure level (SPL) or acoustic pressure level (APL) quantifies the magnitude of a sound field and is expressed in decibels ($\text{dB}$):: $$L_{SPL} = 20 \log{10}{\frac{P}{P_0}}$$ where $P$ denotes the SI unit of root mean square sound pressure mesured in Pascal (Pa), $P_0$ represents the reference sound pressure in air, set at a value of 20 $\mu$Pa [^1]. SPL can be measured using a microphone in air and with a hydrophone in water. 1 Pa = an SPL of $$20\log{10}{\frac{1}{2 \times 10^{-5}}}\text{dB} \approx 94 \text{dB}$$ ### Early decay time (EDT) Early decay time (EDT) is derived from the reverberation time decay $T$, measures the rate of the decay. The difference is the EDT value is evaluated from the initial part, namly the interval between 0 and −10 $\text{dB}$. EDT can be defined by two ways: $$EDT = 6(t_{-10})$$ or $$EDT = \frac{60}{A(0 \text{ dB} \to - 10 \text{ dB})}s.$$ It is considered as a better descriptor of reverberance than $T_{60}$ [7]. ### Sound strength $G$ Sound strength ($G$) relates closely to _loudness_ and represents the difference in sound pressure level (SPL) between an _omnidirectional_ sound source at a specific point in a room and the SPL produced by the same source in an open field, measured at a distance of 10 meters. This measurement is crucial as it reflects the influence of the space on perceived loudness. Specifically, it quantifies the difference in $\text{dB}$ between the level of a continuous, calibrated sound source measured in the space and the level generated by the same source in _anechoic surroundings_ at 10 meters. [7] The formula for calculating the sound strength $G$ is as follows: $$ G = 10 \log_{10}{\frac {\int\limits_{0}^{\infty} P^{2}(t) dt} {\int\limits_{0}^{\infty} P^{2}_{A}(t) dt}}. $$ ### Articulation loss of consonants (ALcons) ### Speech transmission index (STI) ### Clarity #### Clarity50 (C50) #### Definition (D50) #### Clarity80 (C80) ### References [1] R.B. Lindsay, Acoustics: Historical and Philosophical Development, Dowden, Hutchinson & Ross, Stroudsburg, PA 1973, p. 88, Translation of Sauveur’s paper. [https://archive.org/details/isbn_0879330155](https://archive.org/details/isbn_0879330155) [2] Valenzuela, J.; Díaz-Andreu, M.; Escera, C. Psychology Meets Archaeology: Psychoarchaeoacoustics for Understanding Ancient Minds and Their Relationship to the Sacred. Front. Psychol. 2020, 11, 550794. [3] Debertolis, P.; Bisconti, N. Archaeoacoustics in Ancient Sites. A New Way to Analyzing Archaeological Locations. In Proceedings of the 1st International Virtual Conference on Advanced Scientific Results SCIECONF 2013, Žilina, Slovakia, 10–11 June 2013; pp. 10–14. [4] Aletta, F.; Kang, J. Historical Acoustics: Relationships between People and Sound over Time. Acoustics 2020, 2, 128–130. [5] Ramos Amézquita, A. Metodologia de Analisis Acustico de Sitios Arqueologicos de Mesoamerica; Universidad Politécnica de Madrid: Madrid, Spain, 2015. [6] Ramos-Amezquita, A.; Ibarra-Zarate, D.I. Acoustic characterization of three archeological sites in the state of Guanajuato, Mexico. Proc. Meet. Acoust. Acoust. Soc. Am. 2013, 19, 040100. [7] M. Schroeder, Thomas D. Rossing, F. Dunn, W. M. Hartmann, D. M. Campbell, and N. H. Fletcher. 2007. Springer Handbook of Acoustics (1st. ed.). Springer Publishing Company, Incorporated. [^1]: The reference sound presssure $P_0$ is often considered as the threshold of human hearing. It is notable that in an underwater environment, the $P_0$ is set at a value of 1 $\mu$Pa.