Innovative Design and Applications of Materials for Acoustically Performative Indoor and Outdoor Environments II

A special issue of Acoustics (ISSN 2624-599X).

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 14911

Special Issue Editors


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Guest Editor
Department of Energy, Polytechnic University of Turin, 10129 Turin, Italy
Interests: applied acoustics; room acoustics; building acoustics; acoustic materials properties; acoustic simulations; measurement uncertainty
Special Issues, Collections and Topics in MDPI journals

E-Mail Website
Guest Editor
Department of Energy, Polytechnic University of Turin, 10129 Turin, Italy
Interests: classroom acoustics; speech intelligibility; voice monitoring; concert-hall acoustics; acoustic materials; soundscape and sound insulation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The advances in acoustic materials research have been put in the spotlight since the effects of acoustic comfort and noise on health and well-being have become hot topics in the design process. Several projects have seen collaborations among designers and acousticians that address the aesthetic and acoustic issues simultaneously. Such issues have very often involved researchers and innovative industries proposing new solutions to materials design and applications for acoustically performative indoor and outdoor environments. The main design issues have led to recent studies on acoustic metamaterials, which result in applications that hold great promise for the future. However, traditional materials also seem to offer new challenges related to sustainability and environmental impact. On one side, acoustic absorptive and diffusive materials and their combination are still subject to debate not only in musical performance spaces (e.g., concert halls) but also in more common acoustic environments (e.g., classrooms and offices). On the other side, the interest in soundscape design in outdoor environments has recently placed the attention on the opportunities offered by the choice of facade materials and shapes in order to control noise in the urban environment.

This Special Issue aims to bring together contributions that could highlight the potential of new materials and combinations of different acoustic properties in order to maximize their effects on the acoustic performance of indoor and outdoor environments.

This invitation for contributions is addressed to manuscripts in the form of research articles, review articles, and case study investigations that combine theoretical research and applications related to the design, modeling, optimization, fabrication, and acoustic characterization of acoustic materials. Moreover, we invite submissions on real applications and simulations in different environments as well as subjective investigations on the effectiveness of the applications for this Special Issue.

Dr. Louena Shtrepi
Dr. Arianna Astolfi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Acoustics is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • acoustic materials optimization
  • sound absorption
  • sound diffusion
  • sustainable materials
  • acoustic comfort
  • noise control

Related Special Issue

Published Papers (5 papers)

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Research

23 pages, 13789 KiB  
Article
Exploratory Acoustic Investigation of Customizable 3D-Printed Hybrid Acoustic Materials (HAMs) through Interlaboratory Impedance Tube Measurements
by Vaia Tsiokou, Louena Shtrepi, Elena Badino, Arianna Astolfi and Anna Karatza
Acoustics 2023, 5(3), 653-675; https://doi.org/10.3390/acoustics5030040 - 13 Jul 2023
Cited by 3 | Viewed by 2451
Abstract
Acoustic materials are widely used for improving interior acoustics based on their sound absorptive or sound diffusive properties. However, common acoustic materials only offer limited options for customizable geometrical features, performance, and aesthetics. This paper focuses on the sound absorption performance of highly [...] Read more.
Acoustic materials are widely used for improving interior acoustics based on their sound absorptive or sound diffusive properties. However, common acoustic materials only offer limited options for customizable geometrical features, performance, and aesthetics. This paper focuses on the sound absorption performance of highly customizable 3D-printed Hybrid Acoustic Materials (HAMs) by means of parametric stepped thickness, which is used for sound absorption and diffusion. HAMs were parametrically designed and produced using computational design, 3D-printing technology, and feedstock material with adjustable porosity, allowing for the advanced control of acoustic performance through geometry-related sound absorbing/diffusing strategies. The proposed design methodology paves the way to a customizable large-scale cumulative acoustic performance by varying the parametric stepped thickness. The present study explores the challenges posed by the testing of the sound absorption performance of HAMs in an impedance tube. The representativeness of the test samples (i.e., cylindrical sections) with respect to the original (i.e., rectangular) panel samples is contextually limited by the respective impedance tube’s geometrical features (i.e., cylindrical cross-section) and dimensional requirements (i.e., diameter size). To this aim, an interlaboratory comparison was carried out by testing the normal incidence sound absorption of ten samples in two independent laboratories with two different impedance tubes. The results obtained demonstrate a good level of agreement, with HAMs performing better at lower frequencies than expected and behaving like Helmholtz absorbers, as well as demonstrating a frequency shift pattern related to superficial geometric features. Full article
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19 pages, 6098 KiB  
Article
Sustainable Sound Absorbers to Improve Acoustical Comfort in Atria: A Methodological Approach
by Chiara Rubino, Stefania Liuzzi and Francesco Martellotta
Acoustics 2023, 5(1), 280-298; https://doi.org/10.3390/acoustics5010017 - 6 Mar 2023
Viewed by 2418
Abstract
Resource-efficient buildings are one of the most important challenges of the construction industry, which could be achieved by limiting the extraction of natural resources and by replacing them with industrial residues. The present work proposes innovative panels made from textile wastes as an [...] Read more.
Resource-efficient buildings are one of the most important challenges of the construction industry, which could be achieved by limiting the extraction of natural resources and by replacing them with industrial residues. The present work proposes innovative panels made from textile wastes as an efficient solution for making the semi-open atrium in the Polytechnic University of Bari, acoustically suitable for use as an area of study. Several measurements were carried out in the atrium under empty and occupied conditions in order to characterize the sound field of the space (i.e., the reverberation time and the sound pressure level) and the actual sound sources (i.e., the sound power level of the students occupying the space). The on-site measurement results were useful to calibrate a geometrical acoustic model implemented in CATT-Acoustic software and used to predict the effect of the proposed treatments. About 700 m2 of absorbent panels were distributed, leading to a predicted reduction in the reverberation time from 2.4 s to 1.4 s at 500 Hz, and consequently to an estimated 3 dB reduction in sound pressure level, resulting in a reduction in the background noise level due to speech. Furthermore, as a consequence of the “Lombard effect”, a decrease in the background noise level will likely reduce the sound power level of the speakers by 2 dB, with an expected overall reduction of 5 dB. Full article
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16 pages, 9268 KiB  
Article
The Recycling and Reuse of Natural Materials: Sound Absorbing Box Patterns That Use Waste from Olive Tree Pruning
by Rossella Cottone, Louena Shtrepi, Valentina Serra and Simonetta Lucia Pagliolico
Acoustics 2023, 5(1), 177-192; https://doi.org/10.3390/acoustics5010011 - 5 Feb 2023
Cited by 2 | Viewed by 2993
Abstract
The agricultural activity of pruning olive trees generates waste which, due to long-standing practices and unawareness of the consequences, are burned on site, thereby producing CO2 emissions in the atmosphere. Therefore, in order to prevent environmental pollution and a waste of resources, [...] Read more.
The agricultural activity of pruning olive trees generates waste which, due to long-standing practices and unawareness of the consequences, are burned on site, thereby producing CO2 emissions in the atmosphere. Therefore, in order to prevent environmental pollution and a waste of resources, the aim of this research investigation was to highlight some alternative uses of the pruning of olive trees waste. This work focuses on recycled and reused by-products as a secondary raw material for the implementation of interior components that can be used for indoor acoustic correction purposes and evaluates their potential as absorbing materials, without overlooking the aesthetic dimension. In this paper, different configurations based on plywood frames with loose olive pruning chips used as a filler, namely, modules and sub-modules, were investigated. Moreover, other technological details, that is, the influence of a Tissue-Non-Tissue (TNT) layer and a spray film coating applied over the external surface of the loose material, were measured. Sound absorption measurements were conducted inside a small-scale reverberation room (SSRR) and the experimental results demonstrated that the samples, for the given thickness, have weighted sound absorption values (αw) of between 0.15 and 0.35 and single third-octave band values that can reach higher values than 0.50 above 500 Hz. The frequency curves and weighted values of the samples in which the influence of TNT and the spray film coating were tested remained unchanged. This is a design aspect that allows absorbing surfaces to be modeled and integrated with existing walls, while maintaining the acoustic performance and the specific aesthetic features of the loose material. Full article
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13 pages, 3955 KiB  
Article
Numerical and Experimental Validation of Active Vibration Control Logic Performance of a Hybrid Noise Control-Based Brick
by Ilaria Ronconi, Roberta Salierno, Ling Liu, Andrea Giglio, Francesco Ripamonti and Ingrid Paoletti
Acoustics 2022, 4(3), 720-732; https://doi.org/10.3390/acoustics4030043 - 28 Aug 2022
Cited by 1 | Viewed by 2316
Abstract
The limitations of active noise control (ANC) in coping with low frequencies and of passive noise control (PNC) in coping with middle-high frequencies are objects of research that present the potentialities of hybrid noise control (HBC). It aims at combining both of the [...] Read more.
The limitations of active noise control (ANC) in coping with low frequencies and of passive noise control (PNC) in coping with middle-high frequencies are objects of research that present the potentialities of hybrid noise control (HBC). It aims at combining both of the behaviours by broadening the range of absorbed frequencies. Among the several application fields, the AEC (architecture, engineering, and construction) market can take advantage for those applications in which the noise conditions are caused by sound sources that tune in a broad frequencies range. In this frame, the paper describes the numerical and experimental validation of the active behaviour of an under-development project of a hybrid noise control-based acoustic bricks. The latter intends to embed the potentialities of active vibrational noise control (AVC) and passive destructive interference (PDI) in a unique design of an easy-to-mount, 3D-printed, customisable smart acoustic blocks. Active vibration control, the object of this paper, is provided by a 5-mm thick aluminium circular plate with an attached piezoelectric patch. The vibration of the latter, depending on a specific control law, defines the vibration of the plate itself achieving an abatement of the reflection coefficient. Through mathematical modelling and tests in an impedance tube, the results show that the control logic can reach an average abatement of the reflection coefficient of 82% in the frequency range 144–1007 Hz. Full article
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21 pages, 3967 KiB  
Article
A Basic Study on the Design of Dotted-Art Heterogeneous MPP Sound Absorbers
by Kimihiro Sakagami, Midori Kusaka and Takeshi Okuzono
Acoustics 2022, 4(3), 588-608; https://doi.org/10.3390/acoustics4030037 - 31 Jul 2022
Cited by 4 | Viewed by 3121
Abstract
Recently, dotted-art MPPs have been proposed in which a designed pattern is made with the holes. In such a case, the MPP becomes heterogeneous in general. However, existing theories used for the prediction of the absorption characteristics of MPPs assume homogeneity. Therefore, the [...] Read more.
Recently, dotted-art MPPs have been proposed in which a designed pattern is made with the holes. In such a case, the MPP becomes heterogeneous in general. However, existing theories used for the prediction of the absorption characteristics of MPPs assume homogeneity. Therefore, the elaboration of a method for heterogeneous MPPs needs to be performed. In previous work, the authors proposed a method to predict the absorption characteristics of a heterogeneous MPP by using synthesized impedances of each part with different parameters; this is called the synthetic impedance method (SIM) in the present paper. The SIM can potentially be used for various heterogeneous MPPs; however, its scope of applicability needs to be clarified. Furthermore, in proposing a design concept of dotted-art heterogeneous MPPs, the condition that would make the designed MPPs fall within the scope of the SIM needs to be determined. Therefore, in this study, in order to clarify the scope of the applicability of the SIM, twelve samples are first prepared, and then measured sound absorption characteristics and predicted ones are compared and examined in terms of prediction errors. The results show that there are two conditions that should be met to produce predictable heterogeneous MPPs: (1) holes are distributed over the entire surface of the specimen, and (2) the hole spacing is constant. Considering these conditions, a design concept for a dotted-art heterogeneous MPP is proposed: two types of holes, larger holes for the pattern and smaller holes for the background, should be used to meet the above two conditions. Case studies with nine prototypes show that the SIM can make predictions for dotted-art heterogeneous MPPs fabricated according to the concept described above. Full article
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