Architectural Acoustics Research Articles

Ultra-broadband acoustic ventilation barrier based on multi-cavity resonators

The numerical simulations and experimental results of an ultra-broadband acoustic ventilation barrier composed of periodic unit cells are reported in this paper. Based on multiple mechanisms, including sound absorption by eigenmodes of the unit cell and sound reflection by a plate structure on upper surface of the unit cell, a single-layer ventilation barrier with broadband sound reduction is designed, and its working bandwidth can reach about 1560 Hz. The experimental results accord well with the simulation results. Furthermore, two types of three-layer ventilation barriers are designed and demonstrated by using the unit cells with different values of a (the length of the hollow square region) and w (the width of the channel between the adjacent cavities), and the bandwidths of both ventilation barriers can increase to 3160 Hz and 3230 Hz, respectively. The designed barrier structures have the advantages of ultra-broadband sound reduction and ventilation, which paves the way to designing high-performance ventilation barriers for the applications in environmental protection and architectural acoustics.

Reflections on the scientific basis of building-related acoustic standards

As with standards in other indoor-environmental quality, standards play also an important role in building and room acoustics field. They are typically expected to a) represent the state of the art in the respective area and b) arbitrate if a building's design and construction meets the mandated requirements. It is thus important to ensure that the standards' mandates are indeed based on sound scientific evidence. Given their utility as a source of guidance for practitioners, the standards of course need not be conceived as scientific treatises. Nonetheless, the respect for and trust in the standardization bodies and the documents they issue is arguably proportional to the strength of their underlying scientific basis. Given this presupposition, the main intention of the present contribution is to examine, via the review of 19 European, American, and international standards in the domain of building and room acoustic, if they provide, either directly or indirectly, evidence with regard to the included requirements and mandates. The results of this review suggest that the majority of the selected acoustic standards provide sparse references to the evidentiary basis of their mandates. Nonetheless, there are also contrary instances, where standards engage, to some degree, the experimental evidence underlying their mandates. A case study of such an instance displays the potential for future developments in developing explicitly evidence-based standards.

Building and environmental acoustics in obsolete residential neighbourhoods: The case of San Pablo, Spain

In order to establish an agreement between the objectives of acoustic quality in the outdoor environment and the acoustic insulation in a building as required in the current legislation in Spain, the acoustic insulation of typical social housing has been studied in the residential neighbourhood of San Pablo in Seville. Field measurements based on acoustic sonometry have been performed in its public areas, together with the consultations to the strategic noise maps prepared by the administration of the city and with data from a questionnaire answered by neighbours on the perception of environmental and domestic noise. These inputs have enabled calculations of airborne and impact noise insulation in a typical dwelling of the neighbourhood. The neighbourhood presents various kinds of obsolescence, as do many residential estates built in Europe in the same period, mainly in terms of its low quality of construction and structural solutions, its energy poverty, and its typology. Results on acoustic insulation indicate that the requirements of current Spanish legislation have not been met, Dnt,A = 49 dBA, L'nT,w = 80 dB. However, thanks not only to the urban layout of the various types of housing blocks in the neighbourhood, but also to the breadth and abundance of green and common areas and to their roads, the existing environmental sound levels remain below the established limit: Ld < 60 dBA. Hence, the calculation for the external noise insulation in façades indicates that the requirements are met, D2m,nT,Atr = 33 dBA. In the acoustic survey, most people consider the environmental acoustic conditions of the neighbourhood to be acceptable or good and believe that they are barely affected by the domestic noise of next-door neighbours. The research found that social heritage neighbourhoods of the 1960s and 1970s, laid out with cul-de-sacs, curved layouts, and small pockets of parking, significantly improve their urban acoustic performance.

Multiband acoustic reflection metasurface with split hollow cubic

A kind of acoustic metasurface (AMS) with multiple response frequency bands based on the replace method was proposed, which composed of six units, each containing three split hollow cubics (SHCs) (denoted as the AAA type of AMS). The simulation results demonstrated that the presented AMS can achieve the flexible modulation of the reflected wave direction. The AAA type of AMS had one response band, the AAC type of AMS had two different response bands, and the ABC type of AMS had three different response bands. Furthermore, the response bandwidth of the ABC type of AMS declined the most in the middle-frequency band, followed in the low-frequency band, and the least in the high-frequency band, when compared to the corresponding AAA type of AMS with single bandwidth. In addition, it was worth noting that the ABC type of AMS not only enlarged the manipulation direction of reflected acoustic wave, but also improved the effects of the wavefront distribution at the same frequency. This multiple band AMS will be beneficial for the application of architectural acoustics, and acoustic absorption and noise reduction.

Marakeş'teki (Fas) Ben Youssef Medresesi'nin Ses Atmosferleri

This study investigates architectural acoustics in heritage building that is the Ben Youssef Madrasa in Marrakech (Morocco). It aims to characterize the sound atmospheres in this place of learning and community life of el-Tolba (plural of el-Tãleb: student). For this purpose, the study is divided into three parts. The first is the literature review in which we present the definitions of the key concepts, some research on the sound atmospheres in heritage buildings, the different materials and methods used. The objective of this part is to have an overview of the topic of atmospheres. The second consists of architectural conformation reading which is devoted to the identification of the architectural and spatial devices participating in the creation of these sound atmospheres. Special attention was given to the prayer hall as a place of teaching and prayer. The third part focuses on the quantitative characterization of the acoustic environment through computer simulation. The prayer hall and the central courtyard were chosen for the simulation which was done through the Ecotect V5.50. The simulation analysis is limited to three criteria: the uniformity of the sound in the prayer hall, the sound behavior and the degree of the presence of reverberation. The results show that the builders of the madrasa paid attention to the architectural acoustics. Several strategies and devices were adopted to have sound atmospheres appropriate to this building.

Broadband acoustic attenuation in microperforated meta-shells with ventilation

Achieving sound attenuation across a broad frequency range while maintaining adequate ventilation remains a significant challenge in acoustic engineering, as there exists a rigid trade-off between attenuation ability and ventilation. In this Letter, we propose a double-layered microperforated meta-shells to serve as broadband acoustic ventilation barrier. Multiple scattering theory is first employed to characterize sound attenuation performance of the proposed design in terms of both sound absorption and transmission loss, which is not reported before. Experimental result demonstrates a good enhancement of absorption due to the insertion of inner shell with a specific perforation rate of micro cores. The mechanism can be attributed to the inter-cell coupling, which is further utilized to devise a different configuration by wrapping the meta-shell with porous sponge. It is found that adding an extra layer of sponge can further improve the low-frequency attenuation performance. The proposed broadband sound barrier with effective ventilation can find potential applications in architectural acoustics and office noise insulation.

Research on Prediction Method of Objective Assessment of Building Acoustics Based on Machine Learning

The purpose of this study is to predict the objective assessment of building acoustics more accurately and efficiently. In this paper, the neural network technology based on machine learning and computer acoustic simulation technology are combined to extract 10 typical characteristic parameters and 3 target parameters of 800 halls and rooms. Three matrix training sample databases are established by using Odeon platform. The reverberation time and speech transmission index are trained by BP neural network data fitting. The R results of the target parameters in this study are all more than 0.95. The MSE of the reverberation time parameter is in the range of 0.01-0.05 and the MSE of the STI parameter is less than 1 × 10−4. The results show that the neural network has good prediction accuracy, data generalization and application applicability. This prediction method can quickly evaluate the target parameters, reduce manpower and material resources, and improve work efficiency.

A Comparative Study on Acoustic Parameters of Porous Absorber of polyamide, polyester and polyurethane

The analysis and simulation of porous absorbers using COMSOL Multiphysics software is a powerful tool for predicting the acoustic performance of these materials. Porous absorbers are widely used in various industries, including automotive, aerospace, and architectural acoustics. The study aims to provide a better understanding of the acoustic properties of porous absorbers, and the simulation results could be used for optimizing the design of porous absorbers for specific applications. The main objective of this research is to investigate the effect of various parameters on the acoustic performance of porous absorbers, Sound pressure level, scattered acoustic pressure, Incident acoustic pressure, Point pressure, Normal Impedance, Absorption Coefficient. The absorber made from polyamide, Polyester and polyurethane are selected for the studies. The better absorbing results are obtained from the absorber made from polyurethane. The COMSOL software is used to simulate the acoustic behavior of porous absorbers, and the results are compared with experimental measurements to validate the accuracy of the simulation. Keywords: porous absorber, analysis and simulation, acoustic properties, comsol software.

Applying active learning method to improve teaching outcomes in architectural engineering courses

PurposeThis study analyzes the effect of the techniques of active teaching and learning as a way of delivery on the outcomes of quality learning. Focusing on the courses of architectural science taught in a nontraditional method using various active learning strategies, the study takes the case study of the course Building Illumination and Acoustics (BIA) delivered in the academic year 2019–2020 at the University of Sharjah (UoS)'s Architectural Engineering Department (AED).Design/methodology/approachUtilizing both quantitative and qualitative research approaches, the study applied a case study and survey as methods. A questionnaire was designed and performed to assess the level of students' satisfaction with the implemented active teaching method.FindingsThe vibrant learning setting made the students actively engaged and more motivated and enthusiastic. The active learning practices used, including employing senses as in sight and hearing, reasoning rationally and intuitively, reflecting and acting, working steadily and in fits and starts, creating mathematical models, visualizing and memorizing and drawing analogies, were efficient in boosting their ability to comprehend theoretical concepts more effectively. The delivery style effectively enhances quality learning when various active techniques are used pedagogically beyond being merely a utilitarian instrument to prepare novice students of architectural engineering to fulfill practical challenges.Research limitations/implicationsThis article focuses specifically on a theoretical, scientific non-studio course in a particular program of architectural engineering in a particular semester before the dramatic changes in styles of teaching delivery that happened due to the COVID-19 pandemic. Future research could further highlight its results by comparing them to statistical evidence of the development of the course, especially for the duration of online teaching during the pandemic and the hybrid teaching period after it.Originality/valueThis article contributes to the development of teaching and learning of architectural engineering in the local Emirati context by putting original theories of teaching into practice. This paper further contributes to the field of architectural pedagogy in terms of the effect of active learning in the architecture field in the non-studio courses in higher education in the United Arab Emirates.

Modeling impedance boundary conditions and acoustic barriers using the immersed boundary method: The one-dimensional case

Immersed boundary methods are heavily used in computational fluid dynamics, as an alternative to volumetric meshing, when a problem contains irregular geometric features. In wave-based architectural and room acoustics, the dynamics are simplified, but boundary conditions and acoustic barriers are usually described in terms of frequency-dependent impedance and transmittance functions. In this article, a formulation of the immersed boundary method is developed in the informative special case of one-dimensional linear acoustics. It relies on dual driving terms applied to the conservation of mass and momentum equations separately and is directly tunable against boundary impedances and barrier transmittances. It is shown how the driving terms may be combined to model either an impermeable frequency-dependent boundary condition or a barrier with a given transmittance. An explicit time-domain numerical method of finite-difference time-domain type is presented, and it is shown how the immersed boundary condition may be included, at minimal additional computational cost. Special attention is paid to the discrete approximation of the Dirac delta function, necessary in immersed boundary methods, as well as the discretisation strategy for frequency-dependent boundary and barrier conditions. Numerical results are presented. A complete derivation of numerical stability conditions for this immersed boundary method appears in an appendix.

Meta-silencer with designable timbre

Timbre, as one of the essential elements of sound, plays an important role in determining sound properties, whereas its manipulation has been remaining challenging for passive mechanical systems due to the intrinsic dispersion nature of resonances. Here, we present a meta-silencer supporting intensive mode density as well as highly tunable intrinsic loss and offering a fresh pathway for designable timbre in broadband. Strong global coupling is induced by intensive mode density and delicately modulated with the guidance of the theoretical model, which efficiently suppresses the resonance dispersion and provides desirable frequency-selective wave-manipulation capacity for timbre tuning. As proof-of-concept demonstrations for our design concepts, we propose three meta-silencers with the designing targets of high-efficiency broadband sound attenuation, efficiency-controlled sound attenuation and designable timbre, respectively. The proposed meta-silencers all operate in a broadband frequency range from 500 to 3200 Hz and feature deep-subwavelength sizes around 50 mm. Our work opens up a fundamental avenue to manipulate the timbre with passive resonances-controlled acoustic metamaterials and may inspire the development of novel multifunctional devices in noise-control engineering, impedance engineering, and architectural acoustics.

Discussion of impacts of measurement error in architectural acoustics performance specifications

Customers for acoustic products need manufacturers and professionals to provide performance specifications to allow informed design decisions. Acoustic professionals rely upon standard tests and special labs to quantify products. Data published by the ASTM for E90 shows that an STC rating for a single construction can have a variability range of up to 7 points. Being logarithmic, this equates to a sound pressure range of more than 2×, larger than 100%. The log nature of many acoustical performance metrics hides this from most. This large variability causes challenges for the architectural acoustics community. The primary negative impact: customers do not trust the acoustical ratings manufacturers provide. This is not an issue of the manufacturers providing inaccurate information, it is an issue of under-reported and incomplete understanding of the uncertainty in the metrics themselves. For perspective, NRC measured the Young’s Modulus of OSB material to have a mean of 6.8 × 109 and a standard deviation of 1.5 × 108 (Ref: NRC IR-766, Table 22). This yields a measurement error of 3.8%. It is simple to account for this in the design process. If the metric has an uncertainty as large as the acoustic metrics, the standard paradigm for accounting for error not only breaks down, it incentivizes bad actors: cherry picking, lab shopping, etc. More open acknowledgement of the measurement error in architectural acoustic metrics would increase the confidence customers have in them and would allow designers to make more informed decisions.

The creation of functional standards to streamline ASTM standards in committee E33 on building and environmental acoustics

ASTM E33 standards are in wide-spread use in North America in building and environmental acoustics. Some of these standards have been in existence in one form or another for over 60 years. There are now 55 standards within the E33 committee all created by different volunteer authors at different times. Each of these standards is periodically updated by other volunteers. While efforts have been made to keep agreement among these standards, subtle and not so subtle differences creep up in similar measurements, calculations, and specifications. A small working committee has identified 21 topics that are candidates for consolidation into “functional” standards. These functional standards will be used similarly to a computer program function and can be “called” from any other standard. The hope is that this will remove inconsistences among the standards and make the standards easier to read. The current status and future plans of this project will be shared.

Acoustic design trade-offs when reducing the carbon footprint of buildings

Architects and building engineers are increasingly tasked to consider the environmental performance of building designs to meet national and global targets to reduce carbon emissions. While minimizing the carbon footprint is needed to mitigate the effects of climate change, sustainability-driven design can have benefits or unintended consequences on secondary design objectives. Neglect of additional building disciplines could negatively impact the indoor environmental quality in a building and require costly change orders or retrofits. Recent research has shown that sustainability-driven design decisions can affect the acoustical performance in a building, though sustainable and acoustical goals are often unrelated. In response, this presentation reviews acoustic trade-offs when the building design is driven by sustainable goals. Acoustical ramifications and design solutions when minimizing the operational and embodied carbon are discussed. Lastly, areas of future research at the intersection of architectural acoustics and sustainability are provided. Overall, this presentation gives a brief overview on reducing carbon emissions in buildings, discusses the consequences sustainability-driven design can have on building acoustics, and provides sustainable alternatives that do not hinder acoustic performance.

An overview of the proposed new ASTM standard for impulse response measurements using swept sinusoidal signals

This contribution presents the current draft of the proposed ASTM standard for impulse response measurements using swept sinusoidal signals for use in room and building acoustics. After briefly discussing the theoretical background and main body of the proposed standard, the main focus of the presentation is the validation procedure to compare reverberation time measurements between the interrupted noise method and the impulse response method. The challenges and associated uncertainties of the validation procedure are discussed, and preliminary results for rooms of different sizes are shown.

Experimental study of instantaneous sound intensities in rectangular enclosures

Instantaneous and time-averaged intensities are relevant field quantities in architectural acoustics investigations. Modeling of intensity flows in coupled volumes and the effect of absorptive material on its trajectory in reverberation chambers have been studied recently. This work focuses on vortical energy flows with a derivation of instantaneous intensity in enclosed spaces and an experimental effort for investigating the changes over time in all field quantities of interest—instantaneous intensity, pressure, and velocity simultaneously. In this study, the scale modeling technique is applied to investigate instantaneous intensity flows experimentally measured using pressure-3D velocity sensors in a rectangular room. Experimental results suggest the presence of vortical intensity modes at specific frequencies correlated to the room dimensions. The resulting simulation of intensity vortices has potential applications in the acoustical design and analysis of complex room geometries where sound energy flows play a major role in the acoustics of the space such as that of coupled-volume spaces and small rooms for critical listening.

Using machine learning to reconstruct room geometry from an impulse response

Machine learning in room acoustics is an emerging field with great potential yet to be explored. Previous research includes predicting acoustic properties such as the impulse response from visual features that include an image of a room. However, one application that can significantly transform the architectural acoustics design process is reconstructing the room geometry based on its acoustic properties. This paper explores applying machine learning in predicting room geometry from an impulse response. The research aims to provide a tool for architects to design a room based on the desired acoustic experience.

Seeking the Nexus Between Building Acoustics and Urban Form: A Systematic Review.

Noise is penetrating urban life pervasively and is imperative for demonstrating the factors behind it regarding built environment, aka buildings and urban form. So, this review aims to provide a better understanding of the association between building acoustics and urban form characteristics. There is a growing attention for building acoustics, including materials and simulation aspects with various increasing urban form attributes, i.e., the built and natural environment and transportation. Building acoustics is a key aspect of urban life and falls within the interface of various urban form characteristics. While these two main attributes are not sufficiently addressed, they may adversely affect individuals; thus, all the more reason to explore this nexus. This study has evaluated 67 peer-reviewed journal articles after systematically reviewing the triple resources in assessing building acoustics and urban form between 2016 and 2022. This review separates the indoor and outdoor categories within the simulation, theory, building materials, facade, and the built environment sub-categories. The study does not only review the overall scope of present studies but also direct future directions of their associations.

The new buildings acoustic classification scheme in Spain: the standard UNE 74201

In September 2021, the document that develops an acoustic classification scheme was approved in Spain. It is the UNE 74201 standard that is described in this paper. The Spanish ACS is applicable to new and existing buildings for private or public residential use, for health/hospital and educational use. The development of this document has been a challenge which, requested by the construction sector, has been completed after 5 years of collaborative work, within the Technical Committee CTN74/SC2 - Building Acoustics of the Spanish Standardisation Body, UNE. It's been achieved an ACS compatible with the "DB HR" Spanish building acoustics regulations and, in turn, in agreement as much as possible with ISO/TS 19488:2021. The standard defines different levels of noise protection by using a system of six classes for the requirements, A to F, where Class D defines the minimum requirements for acoustic quality that are mandatory to fulfil in the building code. Criteria for airborne, impact and façade sound insulation, for service equipment noise and for reverberation time are included. This paper shows in detail the verification, sampling and class assignment procedures developed in the standard. A comparison of the most general aspects with other European schemes is also shown.

Validation of a potential-based active sound control methodology

This paper describes a global active sound control methodology based on difference potentials in a three-dimensional space. The proposed alternative method allows the reduction of a boundary value problem set in a complex domain to a boundary equation. The only input data needed by the methodology are the acoustic quantities at the perimeter of the protected region. By minimizing the number of input data, the characteristics of the method provide a practical and cost-effective control system. Moreover, these quantities may pertain to the overall acoustic field composed of both the unwanted and wanted components. The most distinctive feature of this methodology is its ability to automatically differentiates between the wanted sounds and unwanted noise within targeted domains. The proposed approach requires information of neither the wanted nor unwanted component separately, but the measurements of the total field on the boundaries of the shielded domain only. This capability can be very useful for the applications related to personal audio and building acoustics as it enables protection of the predefined personal space against the noise coming from the outside. In doing so, the controls will not interfere with the detectors' recognition of the wanted sound or communication among speakers in the room.