1,720,967 research outputs found
Feasibility of a finite-difference time-domain model in large-scale acoustic simulations
Full text linkWave-based techniques for room acoustics simulations are commonly applied to low frequency analysis and small-sized simplified environments. The constraints are generally the inherent computational cost and the challenging implementation of proper complex boundary conditions. Nevertheless, the application field of wave-based simulation methods has been extended in the latest research decades. With the aim of testing this potential, this work investigates the feasibility of a finite-difference time-domain (FDTD) code simulating large non-trivial geometries in
wide frequency ranges. A representative sample of large coupled-volume opera houses allowed demonstration of the capability of the selected FDTD model to tackle such composite geometries up to 4 kHz. For such a demanding task, efficient calculation schemes and frequency-dependent boundary admittances are implemented in the simulation framework. The results of in situ acoustic measurements were used as benchmarks during the calibration process of three-dimensional virtual models. In parallel, acoustic simulations performed on the same halls through standard ray-tracing techniques enabled a systematic comparison between the two numerical approaches highlighting significant
differences in terms of input data. The ability of the FDTD code to detect the typical acoustic scenarios occurring in coupled-volume halls is confirmed through multi-slope decay analysis and impulse responses’ spectral content
Mixing materials in false ceilings to increase sound diffusion in education spaces
No full textAccording to the International standards on education spaces, in situ acoustic tests should achieve specific reverberation time targets. Since the match between predictive formulas and measurements increase with the sound field diffuseness, it is extremely important to pursue such condition through proper design choices. For example, false ceilings can play a key role in controlling room acoustic features; however, the use of such elements is generally considered only for absorption purposes. For this reason, the present work concerns mixing materials in false ceilings within a group of teaching spaces here taken as case studies. The alternation of materials with different acoustic impedances has been investigated through experimental acoustic measurements and numerical models in order to assess the related sound diffusion increase. The ceiling treatment here proposed proved to be an efficient and smart method to exploit diffraction effects along material discontinuities junctions. The match between early design predictive formulas and the results of the acoustic measurements enhanced the reliability of the acoustic design process and set up a potential new guideline for indoor acoustic treatments
Acoustical comfort in university lecture halls: simulating the dynamic role of occupancy
Full text linkThe acoustic comfort in teaching environments is generally
determined through requirements concerning
reverberation time, speech intelligibility and HVAC
noise. The presence of students reduces the reverberation
time but concurrently increases the background
noise, that undermines the focus of students and the
vocal effort of teachers. A double set of measures were
acquired in two university lecture halls in unoccupied
and occupied state to investigate the consequences of
occupancy variations. Acoustic simulations allowed
to assess the dynamic effects of the occupancy detecting
the differences of speech intelligibility. Predicting
the student activity may return reliable outcomes improving
the quality of lessons
The coupled rooms of Odeo Cornaro (1534) as support for Renaissance musicians and soloists
Full text linkThe Odeo Cornaro in Padua (Italy) is a well-preserved XVI Century octangular music space (from Latin the ottangulo) surrounded by communicating smaller halls. Inspired by Roman classicism, the Renaissance architect
Falconetto designed such coupled volume system for the private villa of the Venetian nobleman Alvise Cornaro.
With the aim of assessing the acoustics of the Odeo by means of a contemporary approach, acoustic measurements
were performed, and the room acoustic criteria were derived from the acquired impulse responses.
Experimental results were employed to quantify the acoustic coupling effects throughout the environments and
to outline the acoustic features of the central space. Numerical models were used to assess the free path distribution
and the support given by the ottangulo to the singers’ voices. The main outcomes confirm the different
use of the spaces suggested by historical research: while the main hall was probably employed for singing
and playing instruments, the adjoining rooms were intended for erudite conversations and symposia. The symmetrical
shape and the moderate volume of the central octangular space contribute to creating a neat modal
behaviour that accentuates the sound propagation, highlighting the outstanding value of the Odeo as one of the
“loci resonantes” of the past
MPP sound absorbers investigation to optimize a lecture hall speech intelligibility
No full textThe recent pandemic has drawn attention to the built environment’s hygiene, sustainability, and durability.
Furthermore, studies on micro-perforated panels (MPPs) have recently highlighted their potential for sound absorption in such a context. On the other hand, metal additive manufacturing has become a very popular and convenient method to test acoustic metamaterials (AMMs) performance; however, their deployability in several civil indoor environments and functions still lacks assessment. So, the present work assesses the
suitability of metal 3D printed MPP systems to fulfil speech requirements in lecture rooms. Firstly, an analytical optimization process defined two MPP steel specimens in terms of sound absorption performance.
Secondly, these models were physically manufactured through 3D additive metal printing, and their acoustic performance was measured experimentally on a double-layer configuration. Finally, experimental results were used as input data for characterizing finite-difference time-domain (FDTD) simulations, highlighting the potential enhancement of oral communication through double-layer MPPs on the ceiling of a historical university lecture hall. An FDTD code with a full-spectrum wave-based method was chosen to better handle time-dependent signals, like verbal communication. The outcomes of the process show the influence of the acoustic treatment in terms of reverberation time (T30)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Some Considerations on Sound Propagation in a Cylindrical Worship Space
Full text linkInternational audienceSt John Baptistery in Pisa is a huge space with well-known reverberation effects. The building, recognised as UNESCO world heritage, is a complex space that shows the coupled volumes of galleries - the so-called "matroneum" - and the conical dome. Previous works concerned the calibration of the numerical model of the space. In the present work, a more detailed survey was conducted on acoustic coupling, echo fluttering, and whispering-gallery effects, basing on measurements and simulation. Moreover, the sound decay of the space does not fit the prediction model of scholars. A further aim of the study is to investigate the peculiar typology of free path distribution
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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