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

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

Deadline for manuscript submissions: closed (20 August 2020) | Viewed by 44759

Special Issue Editors

Dr. Arianna Astolfi

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
Dr. Louena Shtrepi

E-Mail Website
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

Special Issue Information

Dear Colleagues,

The advances in acoustic materials research have been put in the spotlight since acoustic comfort as well as noise effects 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 aesthetical 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 which are very promising 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, in recent years, the interest on soundscape design in outdoor environments has 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 potentials of new materials and a combination of different acoustic properties in order to maximize their effects on the acoustic performance of indoor and outdoor environments.

The invitation for contributions is addressed at 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, submissions on real applications and simulations in different environments as well as subjective investigations on the effectiveness of the applications are strongly invited in this Special Issue.

Dr. Louena Shtrepi
Prof. 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 (7 papers)

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Research

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13 pages, 3118 KiB  
Article
Angle-Dependent Absorption of Sound on Porous Materials
by Jose Cucharero, Tuomas Hänninen and Tapio Lokki
Acoustics 2020, 2(4), 753-765; https://0-doi-org.brum.beds.ac.uk/10.3390/acoustics2040041 - 16 Oct 2020
Cited by 14 | Viewed by 5314
Abstract
Sound-absorbing materials are usually measured in a reverberation chamber (diffuse field condition) or in an impedance tube (normal sound incidence). In this paper, we show how angle-dependent absorption coefficients could be measured in a factory-type setting. The results confirm that the materials have [...] Read more.
Sound-absorbing materials are usually measured in a reverberation chamber (diffuse field condition) or in an impedance tube (normal sound incidence). In this paper, we show how angle-dependent absorption coefficients could be measured in a factory-type setting. The results confirm that the materials have different attenuation behavior to sound waves coming from different directions. Furthermore, the results are in good agreement with sound absorption coefficients measured for comparison in a reverberation room and in an impedance tube. In addition, we introduce a biofiber-based material that has similar sound absorption characteristics to glass-wool. The angle-dependent absorption coefficients are important information in material development and in room acoustics modeling. Full article
(This article belongs to the Special Issue Innovative Design and Applications of Materials for Acoustically Performative Indoor and Outdoor Environments)
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12 pages, 2416 KiB  
Communication
The Effect of Deviation Due to the Manufacturing Accuracy in the Parameters of an MPP on Its Acoustic Properties: Trial Production of MPPs of Different Hole Shapes Using 3D Printing
by Kimihiro Sakagami, Midori Kusaka, Takeshi Okuzono and Shinsuke Nakanishi
Acoustics 2020, 2(3), 605-616; https://0-doi-org.brum.beds.ac.uk/10.3390/acoustics2030032 - 14 Aug 2020
Cited by 11 | Viewed by 3542
Abstract
In this study, we discuss the effect of the manufacturing accuracy of a microperforated panel (MPP) produced by 3D printers on acoustic properties through measured and calculated results as a pilot study. The manufacturing costs of MPPs have long been one of their [...] Read more.
In this study, we discuss the effect of the manufacturing accuracy of a microperforated panel (MPP) produced by 3D printers on acoustic properties through measured and calculated results as a pilot study. The manufacturing costs of MPPs have long been one of their shortcomings; however, with recent developments in the manufacturing process, low-cost MPPs are now available. In a further attempt at reducing the cost, 3D printing techniques have recently been considered. Cases of trial production of MPPs manufactured by 3D printing have been reported. When introducing such new techniques, despite the conventional microdrill procedure, manufacturing accuracy can often become an issue. However, there are few studies reporting the effect of manufacturing accuracy on the acoustic properties in the case of 3D-printed MPPs. Considering this situation, in this pilot study, we attempted to produce MPPs with circular and rectangular perforations using a consumer 3D printer of the additive manufacturing type. The hole sizes of the specimens were measured, and the accuracy was evaluated. The normal incidence absorption coefficient and specific impedance were measured using an impedance tube. The measured results were compared with the theoretical values using Guo’s model. Through these basic studies, the MPPs produced by an additive manufacturing 3D printer demonstrated good sound absorption performance; however, due to the large deviations of parameters, the agreement with the theoretical values was not good, which suggests that it is difficult to predict the acoustic properties of MPPs made by a consumer-grade additive manufacturing 3D printer. Full article
(This article belongs to the Special Issue Innovative Design and Applications of Materials for Acoustically Performative Indoor and Outdoor Environments)
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19 pages, 6191 KiB  
Article
The Effect on Room Acoustical Parameters Using a Combination of Absorbers and Diffusers—An Experimental Study in a Classroom
by Emma Arvidsson, Erling Nilsson, Delphine Bard Hagberg and Ola J. I. Karlsson
Acoustics 2020, 2(3), 505-523; https://0-doi-org.brum.beds.ac.uk/10.3390/acoustics2030027 - 04 Jul 2020
Cited by 15 | Viewed by 7592
Abstract
Several room acoustic parameters have to be considered in ordinary public rooms, such as offices and classrooms, in order to present the actual conditions, thus increasing demands on the acoustic treatment. The most common acoustical treatment in ordinary rooms is a suspended absorbent [...] Read more.
Several room acoustic parameters have to be considered in ordinary public rooms, such as offices and classrooms, in order to present the actual conditions, thus increasing demands on the acoustic treatment. The most common acoustical treatment in ordinary rooms is a suspended absorbent ceiling. Due to the non-uniform distribution of the absorbent material, the classical diffuse field assumption is not fulfilled in such cases. Further, the sound scattering effect of non-absorbing objects such as furniture are considerable in these types of rooms. Even the directional characteristic of the sound scattering objects are of importance. The sound decay curve in rooms with absorbent ceilings often demonstrate a double slope. Thus, it is not possible to use reverberation time as room parameter as a representative standalone acoustic measure. An evaluation that captures the true room acoustical conditions therefore needs supplementary parameters. The aim of this experimental study is to show how various acoustical treatments affect reverberation time T20, speech clarity C50 and sound strength G. The experiment was performed in a mock-up of a classroom. The results demonstrated how absorbers, diffusers and scattering objects influence room acoustical parameters. It is shown that to some extent the parameters can be adjusted individually by using different treatments or combination of treatments. This allows for the fine-tuning of the acoustical conditions, in order to fulfill the requirements for achieving a high-quality sound environment. Full article
(This article belongs to the Special Issue Innovative Design and Applications of Materials for Acoustically Performative Indoor and Outdoor Environments)
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23 pages, 3901 KiB  
Article
Improved Room Acoustics Quality in Meeting Rooms: Investigation on the Optimal Configurations of Sound-Absorptive and Sound-Diffusive Panels
by Laura Labia, Louena Shtrepi and Arianna Astolfi
Acoustics 2020, 2(3), 451-473; https://0-doi-org.brum.beds.ac.uk/10.3390/acoustics2030025 - 27 Jun 2020
Cited by 23 | Viewed by 7486
Abstract
This work deals with the improvement of the room acoustic quality of two medium sized meeting rooms through the investigation of the optimal placement of absorption and diffusive panels on the walls and ceiling. Acoustic measurements have been carried out in the existing [...] Read more.
This work deals with the improvement of the room acoustic quality of two medium sized meeting rooms through the investigation of the optimal placement of absorption and diffusive panels on the walls and ceiling. Acoustic measurements have been carried out in the existing untreated rooms with ODEON 13 room acoustics measurement and prediction software, and the Adobe Audition plugins Aurora. Simulations of different combinations of sound absorption and diffusion treatments have been carried out with the updated version of the software, ODEON 15. The panels were positioned in the meeting rooms following the guidelines of the DIN 18041 standard and the scientific literature. The results advise the application of absorptive materials on the ceiling or around the borders, creating a reflective middle area, and on the upper part of one the lateral walls, including the rear wall. Configurations with diffusers do not generally bring significant improvements. The Speech Transmission Index (STI) is a less sensitive parameter for the different acoustic scenarios, compared to Reverberation Time (T) and Clarity (C50). The research also outlined a design workflow, useful to successfully design meeting rooms and rooms for speech in general, which allows to determine the optimal number and location of acoustic panels and to minimize the costs. Full article
(This article belongs to the Special Issue Innovative Design and Applications of Materials for Acoustically Performative Indoor and Outdoor Environments)
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15 pages, 3312 KiB  
Article
Plate-Type Acoustic Metamaterials: Experimental Evaluation of a Modular Large-Scale Design for Low-Frequency Noise Control
by Linus Yinn Leng Ang, Yong Khiang Koh and Heow Pueh Lee
Acoustics 2019, 1(2), 354-368; https://0-doi-org.brum.beds.ac.uk/10.3390/acoustics1020019 - 01 Apr 2019
Cited by 8 | Viewed by 6179
Abstract
For industrial applications, the scalability of a finalised design is an important factor to consider. The scaling process of typical membrane-type acoustic metamaterials may pose manufacturing challenges such as stress uniformity of the membrane and spatial consistency of the platelet. These challenges could [...] Read more.
For industrial applications, the scalability of a finalised design is an important factor to consider. The scaling process of typical membrane-type acoustic metamaterials may pose manufacturing challenges such as stress uniformity of the membrane and spatial consistency of the platelet. These challenges could be addressed by plate-type acoustic metamaterials with an internal tonraum resonator. By adopting the concept of modularity in a large-scale design (or meta-panel), the acoustical performance of different specimen configurations could be scaled and modularly combined. This study justifies the viability of two meta-panel configurations for low-frequency (80–500 Hz) noise control. The meta-panels were shown to be superior to two commercially available noise barriers at 80–500 Hz. This superiority was substantiated when the sound transmission class (STC) and the outdoor-indoor transmission class (OITC) were compared. The meta-panels were also shown to provide an average noise reduction of 22.7–27.4 dB at 80–400 Hz when evaluated in different noise environments—traffic noise, aircraft flyby noise, and construction noise. Consequently, the meta-panel may be further developed and optimised to obtain a design that is lightweight and yet has good acoustical performance at below 500 Hz, which is the frequency content of most problematic noises. Full article
(This article belongs to the Special Issue Innovative Design and Applications of Materials for Acoustically Performative Indoor and Outdoor Environments)
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18 pages, 7397 KiB  
Article
On the Frequency Up-Conversion Mechanism in Metamaterials-Inspired Vibro-Impact Structures
by Anuj Rekhy, Robert Snyder and James M. Manimala
Acoustics 2019, 1(1), 156-173; https://0-doi-org.brum.beds.ac.uk/10.3390/acoustics1010011 - 12 Feb 2019
Cited by 3 | Viewed by 4109
Abstract
Conventional acoustic absorbers like foams, fiberglass or liners are used commonly in structures for industrial, infrastructural, automotive and aerospace applications to mitigate noise. However, these have limited effectiveness for low-frequencies (LF, <~500 Hz) due to impractically large mass or volume requirements. LF content [...] Read more.
Conventional acoustic absorbers like foams, fiberglass or liners are used commonly in structures for industrial, infrastructural, automotive and aerospace applications to mitigate noise. However, these have limited effectiveness for low-frequencies (LF, <~500 Hz) due to impractically large mass or volume requirements. LF content being less evanescent is a major contributor to environmental noise pollution and induces undesirable structural responses causing diminished efficiency, comfort, payload integrity and mission capabilities. There is, therefore a need to develop lightweight, compact, structurally-integrated solutions to mitigate LF noise in several applications. Inspired by metamaterials, tuned mass-loaded membranes as vibro-impact attachments on a baseline structure are considered to investigate their performance as an LF acoustic barrier. LF incident waves are up-converted via impact to higher modes in the baseline structure which may then be effectively mitigated using conventional means. Such Metamaterials-Inspired Vibro-Impact Structures (MIVIS) could be tuned to match the dominant frequency content of LF acoustic sources. Prototype MIVIS unit cells were designed and tested to study energy transfer mechanism via impact-induced frequency up-conversion and sound transmission loss. Structural acoustic simulations were done to predict responses using models based on normal incidence transmission loss tests. Simulations were validated using experiments and utilized to optimize the energy up-conversion mechanism using parametric studies. Up to 36 dB of sound transmission loss increase is observed at the anti-resonance frequency (326 Hz) within a tunable LF bandwidth of about 300 Hz for the MIVS under white noise excitation. Whereas, it is found that under monotonic excitations, the impact-induced up-conversion redistributes the incident LF monotone to the back plate’s first mode in the transmitted spectrum. This up-conversion could enable further broadband transmission loss via subsequent dissipation in conventional absorbers. Moreover, this approach while minimizing parasitic mass addition retains or could conceivably augment primary functionalities of the baseline structure. Successful transition to applications could enable new mission capabilities for aerospace and military vehicles and help create quieter built environments. Full article
(This article belongs to the Special Issue Innovative Design and Applications of Materials for Acoustically Performative Indoor and Outdoor Environments)
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Review

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33 pages, 9632 KiB  
Review
Acoustic Performance-Based Design: A Brief Overview of the Opportunities and Limits in Current Practice
by Elena Badino, Louena Shtrepi and Arianna Astolfi
Acoustics 2020, 2(2), 246-278; https://0-doi-org.brum.beds.ac.uk/10.3390/acoustics2020016 - 01 May 2020
Cited by 19 | Viewed by 9171
Abstract
Current development in digital design, combined with the growing awareness of the importance of building performance, had drawn attention to performance-based design (PBD) in architecture. PBD benefits both design workflow and outcome, allowing one to control the performance of the design proposal since [...] Read more.
Current development in digital design, combined with the growing awareness of the importance of building performance, had drawn attention to performance-based design (PBD) in architecture. PBD benefits both design workflow and outcome, allowing one to control the performance of the design proposal since early design phases. The paper aims to explore its current application in the acoustic field, where its potential is still little exploited in architectural practice. A set of built case studies is collected and briefly analyzed with the aim to shed some light on the state of the art of the application of acoustic performance-based design (APBD) in practice. The analysis suggests that in order to encourage the application of APBD it is needed on one side to enhance the integration and interoperability among modeling and simulation tools, and on the other side to improve the acoustic knowledge and programming skills of the architectural practitioners. Full article
(This article belongs to the Special Issue Innovative Design and Applications of Materials for Acoustically Performative Indoor and Outdoor Environments)
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