Room Acoustics

The increasing complexity and real-time processing demands of audio signals require optimized algorithms that utilize the computational power of Graphics Processing Units (GPUs). Existing Digital Signal Processing (DSP) libraries often do not provide the necessary efficiency and flexibility, particularly for integrating with Artificial Intelligence (AI) models. In response, we introduce TorchFX: a GPU-accelerated Python library for DSP, engineered to facilitate sophisticated audio signal processing. Built on the PyTorch framework, TorchFX offers an Object-Oriented interface similar to torchaudio but enhances functionality with a novel pipe operator for intuitive filter chaining. The library provides a comprehensive suite of Finite Impulse Response (FIR) and Infinite Impulse Response (IIR) filters, with a focus on multichannel audio, thereby facilitating the integration of DSP and AI-based approaches. Our benchmarking results demonstrate significant efficiency gains over traditional libraries like SciPy, particularly in multichannel contexts. While there are current limitations in GPU compatibility, ongoing developments promise broader support and real-time processing capabilities. TorchFX aims to become a useful tool for the community, contributing to innovation in GPU-accelerated DSP. TorchFX is publicly available on GitHub at .

In this paper we present an analysis of the two University of Milan's Auditoria acoustical proprieties and a comparison of the results. The acoustical parameters involved in the measurements were reverberation time, Early Decay Time (EDT), clarity index C80, definition index D50, Initial time delay gap (ITDG) obtained by analysis of binaural impulse response. The comparison of the data have pointed out that one of the auditoria is multipurpose, while the second one is best designed for speech only. The different behavior was explained with consideration on the shape of the hall and on material used in the auditoria.

When the Strehler theatre was planned, its performances from the acoustics point of view have not been taken in the right account. As a consequence, the theatre has now an appreciable visual impact but a poor acoustics. Thanks to the first measurements we have been able to ascribe the main reasons of the lack of good acoustics to the shape and the materials of the hall. Therefore we first suggested some simple operations to improve the acoustics of the theatre. The results have validated our simulation model and we have been able to identify the definitive structural operations for a good listening of music and drama as described in this paper. In 1997 a new theatre was opened in Milano: the Strehler theatre. The theatre was originally planned to host drama only, but later on the management decided to perform musical events too. As the lack of good acoustics came out very soon, the management ask the Acoustic Laboratory of the Milano -Bicocca University to study the problem and to suggest some solution. Regarding the acoustical characteristics, the Strehler theatre is essentially made of three connected sections: the stage, the stalls, and the balcony. Of the three sections the stage has the simplest form: it is shaped after a regular parallelepiped 25 m wide, 16 m long and 24 m high. The only relevant acoustical characteristics is the presence of a false ceiling made of wood rules 10 cm wide and 0.5 cm apart. The base shape of the stalls is an irregular eight sided polygon, with equal paired sides with respect to the symmetry axis. The length of the paired sides are: 18.5 m, 6.5 m, 11.5 m, and 3.5 m respectively. The slope of the stalls places each seat 8 cm higher than the preceding one thus allowing, for all the audience, both a full vision and a good reception of the direct sound originating at the stage. The stalls consist of 550 seats in 16 rows. The gallery, of the same form of the stalls, but with a greater slope, is placed 3 m above the latter. This feature allows the reception of the direct sound from the stage but also a short distance and an acceptable sound intensity. The gallery consists of 404 seats in 8 rows. The theatre, specially designed for drama, turned out to be unsuitable for musical programs but soon displayed some limitation even for drama itself.

This study aims to fill the gap between the endless possibilities of the parametric design process and the detailed acoustic analyses. The developed methodology consists of a custom parametric algorithm that explores the variations of possible interior implementations based on material properties, geometrical formations, and positions in the room to optimize the acoustic response of the space. The proposed methodology assists the design process in the very early phase and explores diverse options. In the first stage, all variations are evaluated in Pachyderm for rapid feedback and to reduce the possibilities for further analysis. The second stage was a detailed evaluation of the first design selection in Odeon and the selection of the best design proposal from the generated. The implemented parametric approach is described, and the final approved design evaluations are presented.

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This paper discusses the concept of the reverberation radius, also known as critical distance, in rooms with non-uniformly distributed sound absorption. The reverberation radius is the distance from a sound source at which the direct sound level equals the reflected sound level. The currently used formulas to calculate the reverberation radius have been derived by the classic theories of Sabine or Eyring. However, these theories are only valid in perfectly diffused sound fields; thus, only when the energy density is constant throughout a room. Nevertheless, the generally used formulas for the reverberation radius have been used in any circumstance. Starting from theories for determining the reverberation time in non- diffuse sound fields, this paper firstly proposes a new formula to calculate the reverberation radius in rooms with non-uniformly distributed sound absorption. Then, a comparison between the classic formulas and the new one is performed in some rectangular rooms with no...

Bei allen Wirbeltieren wird die Lautproduktion durch den Regelkreis aus „Vokalisation / Atmung / Nervus Vagus / Hören“ innerviert und reguliert. Der Gesang von Delfinen und Walen ist Ausdruck und wechselseitige Stimulation einer vegetativen und energetischen Erregung. Es sind Klänge, keine Pfiffe, keine Geräusche und keine sprachähnlichen Laute. Klänge sind raumzeitlich korrelierte, spektral strukturierte, harmonikale Schwingungsmuster. Diese Klänge haben keine Bedeutung, keine Sachinformation und keine Botschaft. Was in diesem vielstimmigen Gesang zu hören ist, das sind keine angeborenen Lautäußerungen. Diese 10 Delphine reproduzieren kein erlerntes Repertoire. In dieser Art des Klingens und Singens kommt etwas zum Ausdruck und wird etwas lebendig, was als eine „schöne Ordnung“, als ein „Klangkosmos“ bezeichnet werden kann. Es ist „polyphoner“ Gesang, auch in der musikalischen Bedeutung dieses Begriffs.

Im Gesang der Delphine hören wir die harmonikale und spektrale, physikalische und arithmetische Ordnung der Klänge und wir können sie verstehen – die Natur des Klangs im Klang der Natur.

("harmonikal" bedeutet: die ganzzahlige proportionale Struktur der Frequenzen in einem Klang: 1:2:3:4:5 …)

Delphine produzieren keine Pfiffe. Das ist physikalisch und physiologisch unter Wasser gar nicht möglich. Schon in der Originallage bei 5-22 kHz, in der wir kaum etwas von den Delphinen hören, ist im Spektrogramm deutlich zu erkennen, daß sie Klangbewegungen erzeugen, hauptsächlich längere Glissandi mit einem großen Ambitus. Es sind gleichmäßige und in der Tonhöhenbewegung sowie der Dynamik variable Klangfiguren, manche sogar in Sinuswellenform (G9→C10→C9→C10). Faszinierend ist, wie sich diese Glissandofiguren überlappen und durchkreuzen, wie sie parallel laufen, alternieren und korrelieren, als könnte man im Klangbild sehen, wie diese Gruppe von Delphinen mit ihren Klängen durch das Wasser gleitet.

Wer den Gesang der Delphine in der mehrfach oktavierenden Verlangsamung gehört hat, kann nur voller Erstaunen erkennen: Welch ein unfaßbarer Klangreichtum, welch „schöne Ordnung“, welche Virtuosität, welche Kreativität, welche klingende und schwingende erregte Lebendigkeit ist in den feinen silbrigen Lauten, dem Knistern, Zirpen und Schnarren der Originallage für unser Wahrnehmungsvermögen verborgen!

Immer wieder ging es mir bei der genauen Analyse des Gesangs der Delphine so, daß ich beim Anblick bestimmter Klangfiguren laut vor mich hin sagte: ‚Das gibt es doch nicht! Das kann doch wohl nicht wahr sein!‘, weil ich unmittelbar so überwältigt war von der Virtuosität, der Kreativität, der Präzision und der harmonischen Ordnung, die ich im  Zusammenspiel der verschiedenen Stimmen entdeckte: wie die Stimmen geführt werden, wie sie aneinander anknüpfen, eine Bewegung oder einen Klang fortsetzen und in ihren Figuren miteinander korrelieren - und dabei auch noch als Gruppe in vielfältiger Bewegung durch das Wasser schwimmen!

Man könnte noch die Frage stellen, ob diese Art des Zusammensingens eine Funktion hat, und sie wie üblich mit der ‚Stärkung des sozialen Zusammenhalts in der Gruppe‘ beantworten. Man könnte aber auch fragen, ob die Delphine „einen Geschmack für Schönes“ haben, wie es Darwin bei den Singvögeln angenommen hat. Und vielleicht ist das Schwimmen-und-Singen einfach ein Spiel, ein  Spiel mit Klängen – ein ‚Klangspiel‘ ohne Sinn und Zweck, ein Spiel der Natur in der „schönen Ordnung“ der Natur der Klänge – in den „Spielräumen“ der Evolution.

📌 I3DA2025 International Conference on Immersive and 3D Audio

📣 Special Session on Resounding the Past: Immersive Technologies and the Heritage Acoustics of Performance Spaces

💁‍♂️ 💁‍♀️ A special session on “Resounding the Past: Immersive Technologies and the Heritage Acoustics of Performance Spaces” will take place as part of the 2025 International Conference on Immersive and 3D Audio (#I3DA) focus on 3D immersive audio including architectural acoustics, virtual acoustics, automotive acoustics, subjective evaluations and listening tests, immersive soundscape design and creative uses of immersive technologies. I3DA 2025 would like to involve academic and industrial researchers to share their latest research, methods, and demos related to Immersive and 3D Audio in Audio Engineering.

➡️ Topics furthermore include heritage acoustics, virtual/augmented reality and their applications, musical acoustics, signal processing in acoustics, non-linear acoustics in auralisation, machine learning related to acoustics, psychoacoustics, 3D audio for gaming, 3D audio in art and sound studies contexts, bioacoustics and the environment.

🏢 The University of Bologna will host this conference from 10th to 12th September, 2025
The Special Session on “Resounding the Past: Immersive Technologies and the Heritage Acoustics of Performance Spaces” will be chaired by our researcher Angela Bellia, scientific advisory board member of the I3DA, along with Antonella Bevilacqua (University of Parma)

🔎 🎶 The session aims to investigate how acoustic modelling and virtual reality (VR), combined with advanced 3D audio technologies such as binaural audio and ambisonics, are transforming our understanding of the relationship between space, performance, and audience.

🙋‍♂️ General Conference Chair: Lamberto Tronchin (University of Bologna)

ℹ️ Find out more here
👉 https://www.i3da2025.org/
The Conference Program is available here: https://easychair.org/smart-program/I3DA2025/

#sonicheritage #Heritageacoustics

Alma Mater Studiorum - Università di Bologna
I3DA 2025

In this paper, I derive the fine-structure constant α as an emergent and parameter-free invariant of Relator theory. The construction uses the Schrödinger equation, classical electrodynamics and mechanics, and Relator geometry with luminal evolution on the C-space and the orthogonal spatial sector R 3 , which xes a minimal phase cavity and the Coulombic baseline. A transverse traceless inductive channel is incorporated through a UV, IR, and OUT decomposition, and a logarithmic closure uniquely determines α with no tted numbers and with no use of measured constants e, c, and ℏ. No quantum electrodynamics is invoked at any stage. The prediction matches the most precise independent measurements at sub-ppt accuracy and remains stable under regulator choices and multipole cutos.

The object of the research was to create a computer model of the Stanisław Moniuszko Grand Theater in Poznań. The scope of the study included changing the parameters of the ceiling over the orchestra pit, while not significantly changing the acoustic parameters of the entire interior. The study attempted to determine whether in the existing (or recently designed) hall, modifying the ceiling parameters could improve the sound quality for the audience. The main parameter was the specific weight of the ceiling. The influence of repositioning the inclined ceiling, its angle of inclination and size was also examined. The result of the conducted tests was unambiguous. The acoustic properties of the hall correlated with the weight of the ceiling acoustically connecting the orchestra with the audience. This is worth noting during the design stage of a concert hall.

The challenge of having good acoustics and visual comfort in lecture theatres was explored in the study. The aim was to evaluate the visual and acoustic comfort levels of users in lecture theatres with a view to establishing their significance in future designs. The study selected seven (7) lecture theatres representing 58.33% out of a total of 12 in Ladoke Akintola University of Technology Ogbomoso as the sample size using simple random sampling techniques. Capacity of each lecture theatres were determined and questionnaires were randomly administered on 4% of the total Users in each. The questionnaire was to determine the hearing audibility levels, visual clarity levels and general comfort/satisfaction levels of users at periods they were receiving lectures. A total of 248 questionnaires were administered. Sources of noise in the lecture theatres were also determined through questionnaire administration. Data were descriptively and inferentially analysed. The study found furniture movements as the major source of noise in the lecture theaters studied. Also, it was realized that there was a significant correlation between users' satisfaction levels and each of visual clarity and hearing audibility (acoustic comfort) despite that users indicated that it was possible for them to hear speaker's speeches without seeing the board; It was hence suggested that determinant factors of these two criteria such as shape of buildings, sizes/volume and sources of noise should be critically put into consideration at design inception stages. Other recommendations that could foster appropriate synergy between acoustic and visual comforts in Lecture Theatres were given.

This study examines the temporal properties of a new form of auditory spatial plasticity called contextual plasticity. The contextual plasticity is a result of adaptation on the time scale of tens of seconds to minutes, but also shows changes at the scale of seconds. The study analyzes behavioral data from an experimental study in which horizontal-plane sound localization was examined in anechoic and reverberant environments (Kopčo et al., 2005). The results suggest that contextual plasticity has a bi-stable component that is strongly adaptive on the time scale of seconds, while overall the effect is building up over tens of seconds/minutes (Kopčo et al., 2007).

The city of Bursa has a multi-cultural background and hosts a diverse architectural heritage inherited from the Roman, Byzantine, Ottoman, and Republican periods. A lost architectural and urban heritage of the city is the Bursa Mevlevi Lodge, which was built between the 17th and 19th centuries. After all the dervish lodges were closed by a law enacted in 1925, Bursa Mevlevi Lodge lost its original function, too. The complex was used for public, residential, and religious purposes until it was demolished in the 1950s due to neglect and abandonment and lost its place in urban memory. Recently, the complex was reconstructed in 2023 and re-functioned as a museum related to Mevlevi culture and Semahane. This article aims to analyze the history and architecture of the complex in the context of Mevlevi culture and Ottoman Mevlevi Lodge architecture. In conclusion, the article reveals that the authenticity of the complex is that it is shaped around the Semahane and identifies its tangible and intangible values and cultural significance in terms of urban history. The article also discusses the justification of the reconstruction as "a controversial heritage conservation method" and the concept of authenticity in the context of contemporary architectural conservation theory.

Using a recently developed real time audio camera, that uses the output of a spherical microphone array beamformer steered in all directions to create central projection to create acoustic intensity images, we present a technique to measure the acoustics of rooms and halls. A panoramic mosaiced visual image of the space is also create. Since both the visual and the audio camera images are central projection, registration of the acquired audio and video images can be performed using standard computer vision techniques. We describe the technique, and apply it to the examine the relation between acoustical features and architectural details of the Dekelbaum concert hall at the

This work deals with the experimental design of hybrid absorbers for broadband noise control in ducts. The followed strategy is the control of input impedance of the multilayer system over a large frequency bandwidth, combining both passive and active technologies. Control of medium and high frequencies is afforded by a porous material backed with an air gap, while low frequencies are reduced with active control. Three active techniques are investigated: pressure-release in the back face of the porous layer, impedance-matching and zero -reflection condition. First experimental results of the developed prototype are shown.

Reproduced a restaurant at one of E.T.S.A.B’s classrooms, we raised to mature the previous experiences though the incorporation of sound absorbent material in the ceilling that allowed us to reduce Rt values to 0.5 s without occupation. We performed this study with real occupation, variable in gender and identical in number and distribution to the previous experiencies. Apliying objectives and subjectives methods, we evaluted the improvement that this new treatment contributes to conversation’s intelligibility. We compared the results obtained in this new study with those obtained in the original experimental situation and theorical study developed in models previously validated.

The assessment of systems’ noise during measurements is usually carried out in an empty state of the spaces under study. Long-term monitoring in real-world conditions can provide insights into the performance of systems during the day. Thus, it becomes useful to find methods able to separate coexisting sound sources in the same space. Clustering techniques can supply the lack of robust methods to perform the segregation. Previous works have shown reliable results about distinguishing human and mechanical noises through sound level meter long-term measurements. Sound pressure levels (SPLs) were post-processed via Gaussian Mixture Model and K-means clustering with a three-step algorithm. The first step is clustering validation and concerns the assessment of the optimal number of clusters among the candidate models. Then, SPLs were divided into the number of clusters obtained by the validation. Finally, statistical and metrical features were used to label the sound sources whether mechanical or human, depending on the algorithm that performed the clustering. Carrying out these algorithms during real-time conditions makes it possible to monitor the actual HVAC noise, providing more accurate analyses. Further studies will focus on broadening the ability to analyze the mechanical noise into its components, such as continuous and discontinuous sources.

A real time room acoustics auralization system for arbitrarily shaped rooms was developed. Virtusound uses an accelerated image source method and a time-dependent radiosity method for the computation of the binaural room impulse response. The total room impulse response is obtained by summing the individual responses from each method. Accelerating techniques and algorithmic improvements are used in Virtusound allowing real time auralization through binaural technology. The current implementation of Virtusound is done on a standard multi-core personal computer..

Directivity pattern of an ordinary loudspeaker becomes more directive at higher frequencies. However, because a single loudspeaker tends to radiate uniformly in all directions at low frequencies, reverberation from surrounding building walls may affect speech intelligibility when installing a multiple-loudspeaker system at crossroads. As an alternative, a sharply directive sound source is recommended to be used, but in many cases the directivity of an ordinary loudspeaker is less sharp at lower frequencies. Therefore, in order to overcome such a limitation, this paper discusses the possibility of using four loudspeakers under active control to realize a quadrupole radiation pattern in low frequency range. In this study, the radiation pattern of a primary loudspeaker and three secondary loudspeakers has been modelled. By placing the loudspeakers close together in the direction of 0 • , 90 • , 180 • , and 270 • , it was theoretically demonstrated that a quadrupole radiation pattern can be shaped in the target frequency range up to 600 Hz by simply controlling the directivity in three of four directions which are 45 • , 135 • , 225 • , and 315 • . Although, the radiation pattern model is far from realistic configurations and conditions, it is possible to realize a quadrupole radiation pattern in the low frequency range.

Si nous sommes habitués à topographier, photographier, ou décrire les grottes, quid de leur dimension sonore ? Pour pallier ce manque d'informations nous avons investi la grotte du Déroc à Vallon-Pont-d'Arc afin d'y appréhender la dimension acoustique. A partir d'observations à la voix et à l’oreille, nous avons repéré les zones de résonance ; soit sur une fréquence
isolée, soit sur une partie du spectre vocal, ou encore les zones où une réverbération du son est remarquable. Ensuite, pour étudier ces espaces acoustiques repérés, nous avons mesuré leur réponse en fréquence et leur temps de réverbération. Pour cela nous utiliserons la méthode de déconvolution, qui consiste à émettre et enregistrer un bruit bien choisi, puis à comparer le signal émis au signal reçu. Cela donne une identité acoustique propre à l'espace étudié. Dans notre cas, nous émettons tour à tour un son continu dont la fréquence varie de 20 à 20 000 Hz, et une impulsion de bruit blanc produite par l'éclatement d'un ballon de baudruche. Cette étude acoustique au Déroc nous amène à nous interroger sur l'approche archéoacoustique déjà réalisée par le passé.

This paper describes the design principles underlying the Round Robin Test (RRT) carried out among the laboratories of the Sound Absorption working group of the Italian Standardization Body (UNI). In recent years, the determination of the measurement uncertainties in the fields of building and room acoustics has attracted increasing attention. In particular, sound absorption in a diffuse sound field might be difficult to determine, especially for very highly absorptive materials. Results coming from different laboratories cannot always be compared, due to differences in the actual sound field found in nominally equivalent facilities. During this RRT, carefully selected samples have been measured in the reverberation rooms of the different laboratories participating in the RRT according to standard ISO 354 in force as well as the newly proposed draft. The procedure will be presented in the paper.

Acoustic Intelligibility is one of the great important subjects for the performance of many environments such as catholic churches. Such places are used for many types of performances requiring adequate intelligibility for speech and clarity for music. The acoustic performance of worship places has been studied for a while because such places can accommodate not only religious events but also different kinds of events related or not to religion. Along Catholicism history, the church as an institution has been changing over the years the procedure of its rituals such as the mass and opening their temples to other kinds of performances making the acoustic performance of such environments require great deal of complexity. This research analyzed six catholic churches in the city of Campinas, Sao Paulo, Brazil. Churches were chosen according its period of construction and architectural typology. The objective of this research is to study the acoustic performance of these churches and establish a relationship with the architectural characteristics of the temple. Measurement of acoustic parameters such as Reverberation Time (RT), Early Decay Time (EDT), Clarity Index (C80), Definition (D50) and Speech Transmission Index (STI) were used to analyze the acoustic performance of the churches. Measurements were done according to ISO 3382-1:2009. Churches can be considered performance spaces due to its broader possibilities of use, making it possible to compare its data with other similar researches. Results were also analyzed according to procedures specifically proposed for those spaces found in the literature making it possible to qualify the acoustic behavior of churches for each specific use and allowing further studies and comparisons.

The mathematical properties of the Laplacian on a bounded domain are well-known when the boundary condition is of the first type (Dirichlet), or second type (Neumann). In both cases, this operator is self-adjoint and, therefore, diagonalizable, its spectrum is discrete, and the set of eigenfunctions can be chosen to form an orthonormal basis of the Hilbert space of square-integrable functions on the domain. However, in the case of the third type (Robin) boundary condition, the same is true only when the parameter is real-valued. On the contrary, when this parameter is complex-valued, the Laplacian may not even be diagonalizable. In this paper, the spectral decomposition of the complex Robin Laplacian is investigated in the most general case possible, and a formula that decomposes any square-integrable function on the set of its (generalized) eigenfunctions is provided. This result is applied to the Green's function of the Helmholtz equation, whose existence, unicity and closed-form expression are established in this general setting, and the statistical wave field theory, which provides the statistical laws of waves propagating in a bounded domain.

Echo and sound resonance in a conference room cause obscure speech and make listeners tired. Thus, the acoustical properties of a conference room are vitally important. The conference room 412 at Sharif University Physics Department failed to meet basic acoustical standards. The aim of this research is to improve reverberation time (RT) of the conference room using Helmholtz resonators with defined dimensions, diffusers, and sound absorbers. Helmholtz resonators are widely used to absorb sound noise especially at low frequencies. They are particularly useful when noise has a narrow-frequency band. One of the advantages of using Helmholtz resonators is their capacity to be tuned on different frequencies. We enhanced acoustical properties of Helmholtz resonators using proper absorbers and diffusers. In order to decrease the RT, a large number of Helmholtz resonators have been made and installed in proper positions in the conference room. The RT was measured before and after installati...

This paper presents a method to synthesize the acoustic assessment of large reverberant places of worship for two types of sound stimuli: music and speech. The proposed synthetic indices are derived from the spectrally and spatially averaged values of various acoustic parameters, related to the attributes of perceived sensation and widely considered in other acoustic studies. Partial indices associated with each parameter are determined by comparing its average value with its range of optimum values and its environment of acceptable values that are set according to their respective differential thresholds (JND). The methodology implemented is applied to the acoustic assessment of five cathedrals of Andalusia.En este trabajo se presenta un método para sintetizar la valoración acústica de grandes espacios reverberantes de culto para dos tipos de estímulos sonoros, la música y la palabra. Los índices sintéticos propuestos se obtienen a partir de los valores promediados espectral y espa...

The most significant acoustic parameters in a set of mudejar-gothic churches were measured (all the churches were located in the city of Seville). From the analysis of these data important conclusions were otained about the behavior of the reverberant field versus source–receiver distance [J. Sendra et al., Computational Acoustics and its Environmental Applications—II (Computation on Mechanics Publications, Southampton, 1997), pp. 139–148] from Barron‘s revised theory [Barron et al., J. Acoust. Soc. Am. 84, 618–628 (1988)] and the relations between several acoustics quality descriptors: C80, D50, and RASTI [Zamarreno et al., Proceedings Acustica-98, Lisbon (1998)]. The three most representative churches were chosen to carry out a computer simulation with the raynoise software. Absorption coefficient values used in the model have been adjusted using measured reverberation time data, and thus the results were obtained for the other acoustic parameters in the different octave bands. It...

Continuous tone underwater reverberation is the signal observed when the transmitting and receiving transducers are in linear motion, the transmitter is operating at a single frequency, and no major reflecting bodies are in the beam paths. This reverberation has been measured as a function of frequency for ocean depths of 9.5 to 85.7 meters, at transducer speeds up to 7.5 meters per second, and for various sea states. The techniques for measurement are described, and some typical reverberation spectra are shown. The spectra are shown having maxima at approximately the frequency corresponding to the Doppler shift caused by the transducer motion. The spectra are asymmetrical about the maximum, with the general reverberation level decreasing with increasing depth and decreasing sea state.

Taking the Myx Sail displayed at the Danish Design Museum as a case study, this article investigates the room acoustics of an architectural installation made of Mycelium Textiles. Mycelium Textiles represent a novel typology of mycelium-based composites (MBC). The Myx Sail absorbers are grown on a composition of different layers of plant fibres combining woven jute textile with hemp mat and loose wood wool substrate enhancing the mechanical and acoustic properties of the composite. Two complementary acoustic tests were conducted to measure the absorbing properties of the mycelium material and its effects on the acoustics of the exhibition hall. The results show that the sail acts effectively as an acoustic absorber especially in higher range of frequencies, reducing the reverberation time and improving speech intelligibility. The effect of the sail on the overall room acoustics is especially effective, if the sound source is placed directly underneath the sail. The results of a complementary survey amongst visitors on their subjective perception of comfort and well-being however indicate that the degree to which a grown surface (and by extension, a grown building) is perceived positively or negatively depends on the relationship the individual has with Nature.

The performance of a speech recognizer is degraded drastically in reverberant environments. We proposed a novel algorithm which can model an observation signal by composition of HMMs of clean speech, noise and an acoustic transfer function(l]. However, how to estimate HMM parameters of the acoustic transfer function is a remaining serious problem. In our previous paperll], we measured real impulse responses of training positions in an experiment room. It is inconvenient and unrealistic to measure impulse responses for every possible new experiment room. This paper presents a new method to estimate HMM parameters of the acoustic transfer function from some adaptation data by using an HMM decomposition algorithm which is an inverse process of the HMM composition. Its effectiveness is confirmed by a series of speaker dependent and independent word recognition experiments on simulated distant-talking speech data.

A model on nonlinear sound reverberation of enclosures will be presented. The classical statistical theory of sound propagation in enclosures has been enlarged to include non linear excitation signals. Numeric computations as well as experimental results indicate reverberation times shorter than under linear conditions. An equation relating reverberation time under nonlinear conditions with reverberation time under linear conditions through an intensity nonlinear parameter has been derived. Some repercussions on experimental room acoustic studies (actual and reduced scale room models) will also be commented.

A speech signal captured by a distant microphone is generally smeared by reverberation, which severely degrades automatic speaker recognition performance. To improve system performance, an effective and robust method is proposed to extract features for speech processing. In this paper, a room impulse response is presumed to comprise of three parts: a direct-path response, early reflections and late reverberations. Since late reverberations are known to be a major cause of system performance degradation, this paper focuses on dealing with the effect of early reflection because the early reflections and their properties play a necessary role within the acoustics of an enclosure. The proposed method first estimates the early reflection using autocorrelation function from the presentation of speech signals in the first stage, the estimates are combined with an anechoic signal for use into training the system in the second stage. The employed method looks to be promising, achieving a substantial improvement in system performance relating to reduced equal error rate and detection trade-off, especially at longer reverberation time.

The material properties of a piezoelectric continuously twisted structurally chiral medium (PCTSCM) vary helicoidally along the axial direction. Monochromatic axial wave propagation in a PCTSCM has been solved exactly [A. Lakhtakia, Appl. Acoust. (in press)]. It is shown that specific axial propagation modes are related to specific piezoelectric coupling coefficients. By a judicious choice of these coefficients, one may control certain sets of modes independently of other sets of modes. Since the degree of piezoelectric coupling can be engineered, PCTSCMs are promising candidates for future transduction devices. Emphasis has been placed on PCTSCMs with hexagonal symmetries. Graphical support of the conclusions will be presented. [Work supported by NSF.]

Díaz-Andreu, Margarita, Álvarez-Morales, Lidia and Santos da Rosa, Neemias. (2025) The archaeoacoustics of rock art sites: a methodological review. In Pamela Jordan, Sara Mura and Sue Hamilton (eds.) New Sensory Approaches to the Past: Applied Methods in Sensory Heritage and Archaeology, 255-284. London, UCL Press. | ABSTRACT: In this article, our aim is to present a comprehensive review of the evolution of the methods applied in the archaeoacoustics of rock art sites, from the pioneering studies by Glory and Reznikoff, to the advanced methods based on Ambisonics techniques and GIS technology used nowadays by the ERC Artsoundscapes project. We will also introduce the frontier research, but still preliminary work, undertaken in the fields of psychoacoustics and neuroacoustics, both incorporated into the project in an attempt to explore listeners' subjective experiences and physiological responses to the acoustics of the rock art sites. The strengths and weaknesses of the different approaches are discussed, providing an insight into their potential application. Our intention is for this text to stand as a valuable resource for current and future generations interested in working in the field, as well as a positive contribution to the debate on the necessity of standardising an experimental method for conducting acoustic research in rock art sites for more consistent, repeatable, and comparable results. || SECTIONS: The first 50 years of the archaeoacoustics of rock art sites up to 2018 ~ The pioneers: Glory and Reznikoff ~ From human-made sounds to impulsive sounds – early archaeoacoustic research ~ Capturing more reliable IRs: using loudspeakers as the sound source | Gathering 3D sound information: A methodological evolution towards high quality auralizations ~ The measurement procedure and main pieces of equipment used ~ Performing a comprehensive analysis of the acoustic features rock art sites ~ Approaching past sounds from the field of psychology | GIS applied to archaeoacoustic and perceptual research | Conclusions

The acoustic quality of commercial spaces is often a problem confronting the designers. Ensuring adequate speech reception in relation to sound alarm systems in such spaces is one of the key factors determining the acoustic quality of a space. The aim of this paper is to present an initial, index-based method for the assessment of the acoustic quality of commercial spaces and buildings during the design process, taking into account selected architectural and acoustic parameters. The development of the method is based on acoustical computer models, literature and analyses of building types. The acoustic quality of commercial spaces and buildings is determined by speech intelligibility, which is mainly influenced by reverberation time within an enclosure. This is why analyses were focussed on reverberation time and other parameters related to speech intelligibility. Analyses concerning three types of commercial spaces: shops, corridors/shopping streets and atriums. For each type of the space there is a separate selection of main architectural and acoustical parameters having influence on the acoustical climate of the commercial enclosures and buildings. The presented method, separate for each commercial type, is expected to provide an easy-to-use assessment of a commercial space designed in terms of speech intelligibility, as required for sound alarm systems, conforming among other things, to applicable standards. The method is a practical tool for design and decision-making community: architects and designers. By applying this method, it is possible to increase the safety of commercial spaces and buildings occupants and reduce or avoid costs associated with improving the acoustic conditions of ready-to-use commercial spaces and buildings.

In this paper, the late part of a room response is modeled in the frequency domain as a complex Gaussian random process. The autocovariance function (ACVF) and power spectral density (PSD) are theoretically defined from the exponential decay of the late reverberation power. Furthermore we show that the ACVF and PSD are accurately parametrized by an autoregressive moving average (ARMA) model. This leads to a new generative model of late reverberation in the frequency domain. The ARMA parameters are easily estimated from the theoretical ACVF. The statistical characterization is consistent with empirical results on simulated and real data. This model could be used to incorporate priors in audio source separation and dereverberation.

A simulation system based on Building Information Modeling (BIM) software can speed the prediction of the acoustic performance of an indoor space during the schematic building design stage. This claim is demonstrated by a software prototype that is composed of four modules: BIM data extraction module, frequency analysis module, sound effect simulation module, and auralization/visualization module. After giving a BIM of a room additional custom parameters to express acoustic qualities of materials, the BIM data extraction module retrieves necessary information such as room dimensions, and absorption coefficients of surfaces. The frequency analysis module identifies dominant frequencies in a sample sound track file. The sound effect simulation module reads extracted BIM data and the frequency composition information and calculates reverberation time and sound intensity level (SIL). The auralization/visualization module applies the results from the previous step to modify the sound tra...

An exchange rate of Rs. 45.45 for a dollar has been used in this case study. The exchange rate varies considerably. 2 () 3 The glossary provides definitions of terms used in this case study. 4 Similar problems were also identified in the acoustical studies done in seven Danish halls by Neil Werner Larsen and team, and it was revealed that the excessive use of PA in front of the stage combined with a long reverberation time in low frequencies was the main cause of this acoustic problem.

An impulse response of an enclosed reverberant space is composed of three basic components: the direct sound, early reflections and late reverberation. While the direct sound is a single event that can be easily identified, the division between the early reflections and late reverberation is less obvious as there is a gradual transition between the two. This paper explores two statistical measures that can aid in determining a point in time where the early reflections have transitioned into late reverberation. These metrics exploit the similarities between late reverberation and Gaussian noise that are not commonly found in early reflections. Unlike other measures, these need no prior knowledge about the rooms such as geometry or volume.

Teachers often report voice problems related to the occupational environment, and voice problems are more prevalent in teaching than in other occupations. Relationships between objectively measurable acoustical parameters and voice use have been shown. Speakers have been shown to be able to predict the speaker-comfort of an environment. Teachers with voice problems use the room differently than their voice-healthy controls. The aim of this study was to investigate what vocal changes speakers do in different acoustical environments and noise conditions. Nine female speakers, voice patients, and voice-healthy were exposed to four controlled, acoustical “environments” mounted in the same room: 1. stripped; 2. wall- and ceiling mounted absorbents; 3-4 as 2 but with extra ceiling absorbents and in two positions. The speakers were recorded with voice-accumulator and simultaneous voice recordings and spoke freely for 3-5 min in three noise conditions in each setting: silence, classroom noi...

Classroom acoustics not always take the speaker's comfort into consideration. The purpose of the presented papers was to investigate voice use, vocal behavior and prevalence of voice problems in Swedish teaching staff. Ratings of features in the work-environment on voice use were explored in n = 487 teachers. Based on their answers the respondents were split into two groups: teachers with self-assessed voice problems and voice-healthy teachers. Teachers with voice problems and were matched to a voice-healthy colleague from the same school and were investigated and compared for clinical findings and for vocal behavior. Acoustic properties of their teaching environments were measured. Teachers with voice-problems were more affected by any loading factor in the work-environment and were more aware of the room acoustics. Differences between the groups were found during field-measurements, while there were no differences in the findings from the clinical examinations of the larynx an...

Teachers have high occupational voice demands. The voice load of teachers is both environmental and individual. Little is known about the teachers' own view of the contribution from the environment and about the teachers' voice use at their work-place. Aim: The purpose was to investigate the voice use and prevalence of voice problems in teachers and to explore their ratings of vocally loading aspects of their working environment. Method: A questionnaire-survey in 467 teachers aiming to explore the prevalence of voice problems in teaching staff identified teachers with voice problems and vocally healthy colleagues separated in two groups, teachers with self-assessed voice problems and vocally healthy teachers. Teachers with voice problems were further, matched to a voice healthy colleague from the same school. The pairs were investigated and compared for clinical findings and for vocal behavior in the teaching environment and aspects of the classroom environment were also measured. Results: Teachers with voice problems were more affected by any loading factor in the work-environment and were more perceptive of the room acoustics. Differences between the groups were found during field-measurements of the voice, while there were no differences in the findings from the clinical examinations of larynx and voice. Conclusion: Teachers suffering from voice problems react stronger to loading factors in the teaching environment. It is in the interplay between the individual and the work environment that voice problems emerge.

Many teachers suffer from voice problems, and classroom acoustics has been considered as one of the potential hazards for this. The present study examines how classroom acoustics interacts with the voices of 14 teachers without voice problems and 13 teachers with voice problems. The assessment of the voice problems was made with a questionnaire and a laryngological examination. During teaching, the sound pressure level at the teacher’s position was monitored. The teacher’s voice level and the activity noise level were separated using mixed Gaussians. In addition, objective acoustic parameters of reverberation time and room support (based on early reflections) were measured in 30 empty classrooms of the study. An empirical model shows that the measured voice levels depend on the activity noise levels and the support. Teachers with and without voice problems were differently affected by the support of the classroom. The results thus suggest that teachers with voice problems are more a...

This article explores how wave motion principles are applied in architectural acoustics to enhance sound quality in built environments such as theaters, classrooms, and temples. It examines key acoustic phenomena-reflection, absorption, interference, and reverberation-and their role in the design of functional spaces. Case studies like the Teatro Colón and Walt Disney Concert Hall demonstrate how geometry, materials, and simulation technologies influence sound propagation. The study also emphasizes the importance of wave behavior not only in acoustic performance but also in structural resilience to seismic activity.

El control de la realimentación acústica en los sistemas de refuerzo sonoro requiere una adecuada planificación, ya que cuando se cierra el lazo de realimentación, en cualquiera de sus grados, las consecuencias son indeseables. Una herramienta que permita su predicción puede resultar de gran ayuda, tanto en el ámbito profesional como en el ámbito docente. En el primer caso permite al ingeniero de sonido planificar y simular, previendo las condiciones que pueden provocar inestabilidad, en el segundo caso puede usarse como herramienta de formación para futuros ingenieros de sonido, simulando situaciones no siempre accesibles que faciliten la comprensión y el tratamiento del fenómeno. La herramienta desarrollada se ha dividido en secciones cada una en su contexto (acústico, electroacústico y geométrico), lo que creemos facilita una actuación más directa con parámetros de una misma clase, separando además las causas particulares del fenómeno.

La memoria tratta delle problematiche acustiche degli ambienti per ufficio di tipo open plan. Vengono analizzate le principali configurazioni tipologico-funzionali che questi ambienti possono assumere e vengono individuate in particolare sei tipologie spaziali per le quali viene valutata la variazione di alcuni descrittori acustici (decadimento lineare, distanza di distrazione, tempo di riverberazione, STI) mediante il software raytracing Ramsete®. La recente letteratura tecnica è coerente nell'affermare che gli open plan office presentano condizioni ambientali peggiori degli uffici tradizionali a causa della mancanza di spazio individuale, della carenza di requisiti acustici, termici e di privacy, oltre che della cattiva qualità dell'aria e dell'elevata possibilità di distrazione per i lavoratori. Inoltre esiste una relazione evidente tra le qualità fisico-ambientali e le prestazioni dei lavoratori, nonché tra le stesse qualità e la soddisfazione degli impiegati verso il lavoro svolto. Nonostante questo, gli open plan office sono molto diffusi, soprattutto per le qualità economiche positive che rappresentano per i datori di lavoro. Il comfort acustico può essere definito come quella particolare condizione psicofisica per cui un individuo, immerso in un campo sonoro, si trova in condizioni di benessere rispetto all'attività che sta svolgendo. Esso è condizionato da fattori diversi che interagiscono tra loro come le caratteristiche fisiche della sorgente (la potenza sonora, lo spettro, la durata e l'andamento nel tempo), le caratteristiche dell'ambiente (la riflessione e la diffusione del suono), le caratteristiche individuali dei soggetti esposti (la sensibilità al disturbo e l'acuità uditiva) e l'attività svolta nello spazio analizzato. Due requisiti essenziali per la qualità acustica degli ambienti interni sono l'assenza di eccessivo disturbo e la buona ricezione.

Background noise levels and Reverberation Times were measured in 34 unoccupied classrooms. From these measurements, the values corresponding to different degrees of classroom occupancy were estimated, together with Speech Intelligibility. Results show that most unoccupied classrooms do not meet the required criteria, while in occupied classrooms the requirements are met only for medium/high levels of occupancy.