Room Acoustics Research Articles

Latency-free real-time auralisation in hemi-anechoic chambers

Real-time auralisation allows users to interact with a simulated acoustical room, providing a more responsive way of evaluating acoustical performance than pre- recorded auralisation. Nevertheless, real-time auralisation is computationally intensive and, therefore, susceptible to latency. This paper presents a novel latency-free real-time auralisation method that enables users to auralise a simulated acoustical event with self-excitation more accurately than current methods. The method uses a loudspeaker system inside a hemi-anechoic chamber. By exploiting the inherent floor reflection of the hemi-anechoic chamber, the impulse response can be trimmed to compensate for the total latency of the loudspeaker system. The method's validity is demonstrated with measurements presenting virtual wall reflections arriving at the correct time at the listening position. The influence of the speaker placement regarding latency is discussed. This method enables users to evaluate a given response more accurately than conventionally possible.

Raumakustische Planung von ­Großraumbüros gemäß ASR A3.7

Room acoustic planning of open-plan offices in ­accordance with ASR A3.7 Room acoustic verification for office use is generally carried out in accordance with the recommendations of DIN 18041. The introduction of the workplace regulation ASR A3.7 “Noise” in 2018 formulated additional requirements that can affect the dimensioning of room acoustics measures. This article summarizes practical experience in the acoustic planning of open-plan offices and examines the extent to which the target values described in ASR A3.7 are in line with the protection goals of occupational health and safety.

Directional Sound Field and Spatial Speech Decay: Impact of Sound Absorption and Screen Height in Performance Spaces and Open-Plan Offices

This study investigates the spatial decay rate of speech in performance spaces and open-plan offices, focusing on the effects of sound absorption and screen height. Utilising parameters such as D2, SD_2, SD2, S (decay rate) and Lp, A, S, 4mL_p, A, S, 4mLp, A, S, 4m (sound pressure level at 4 meters), the research evaluates how acoustic environments impact speech transmission. Through detailed experiments on different screen heights (1.2 m, 2.1 m, and 2.9 m) and material absorption, it was found that increasing screen height significantly reduces the spatial speech decay in open-plan offices, but only up to a certain threshold. The results suggest that while acoustic enhancements like screens and absorptive materials improve speech privacy, over-reliance on single- number ratings can lead to misclassification of office acoustics. This research provides insights for optimising room acoustics, ensuring speech privacy, and meeting acoustic comfort standards.

In situ acoustic characterization of a perforated panel on a cavity by means of PU measurement and model fitting

The in situ characterization of materials is a crucial challenge in room acoustics, as laboratories measurement cannot always be applied in consultancy practices. In particular, there is a lack of method to characterize in situ systems with perforated facings, which are commonly encountered systems in room acoustics. In this paper, the in situ characterization of a rigidly-backed porous material behind a rigid perforated facing by means of pressure–velocity measurements is presented. The method includes an inverse impedance model fitting based on measurement in a limited frequency range. The applicability of this method was studied by measuring a variety of perforated facings, whether in front of an air cavity or backed by a porous layer, and comparing the obtained impedance model parameters to reference values. Good agreement was observed between the retrieved parameters and the references, with the errors in all retrieved parameters moving mass, facing thickness, cavity depth, porous layer thickness and porous layer flow resistivity not exceeding 15%.

Cognitive load associated with speaking clearly in reverberant rooms

Communication is a fundamental aspect of human interaction, yet many individuals must speak in less-than-ideal acoustic environments daily. Adapting their speech to ensure intelligibility in these varied settings can impose a significant cognitive burden. Understanding this burden on talkers has significant implications for the design of public spaces and workplace environments, as well as speaker training programs. The aim of this study was to examine how room acoustics and speaking style affect cognitive load through self-rating of mental demand and pupillometry. Nineteen adult native speakers of American English were instructed to read sentences in both casual and clear speech—a technique known to enhance intelligibility—across three levels of reverberation (0.05 s, 1.2 s, and 1.83 s at 500–1000 Hz). Our findings revealed that speaking style consistently affects the cognitive load on talkers more than room acoustics across the tested reverberation range. Specifically, pupillometry data suggested that speaking in clear speech elevates the cognitive load comparably to speaking in a room with long reverberation, challenging the conventional view of clear speech as an ‘easy’ strategy for improving intelligibility. These results underscore the importance of accounting for talkers' cognitive load when optimizing room acoustics and developing speech production training.

Ten questions concerning Architectural Acoustics

Building and room acoustics are relatively modern architectural and engineering disciplines. Nevertheless, acoustics was also a concern for buildings in the past, e.g., in theatres in ancient Greece and in Roman times. Nowadays, we spend 80–90 % of our time indoors, and sound impacts our communication and actions in an environment to a great extent. Therefore, acoustic aspects should be considered appropriately in the Environmental Quality and Global Comfort context as part of the overall aspects of building physics, although other factors (e.g., thermal, air quality, etc.) are conventionally considered more “mainstream”. The ten questions considered in this paper range from the basic definitions underlying the differences between building and room acoustics, to more applied topics about how to measure, simulate and use acoustic data in the design of the built environment. Significant research activities have been conducted by acoustic experts on different aspects related to the measurements of physical properties, perceptual aspects and technological development in both the physical and virtual dimensions, thereby paving the way towards a more inclusive and healthier acoustic environment. Apart from illustrating the current state of the art, the answers to these questions point out the still existing gaps in the field and future challenges, thereby highlighting the new competencies required to support the design of the acoustic environment, focusing on the physical, physiological, and psychological needs of the users.

Reduced noise in the emergency department: the impact on staff well-being and room acoustics

Background and introductionThe ED is often perceived as noisy. Excessive noise has deleterious effects on health and productivity. This study evaluated if a package of noise-reducing interventions altered workload, physical...

The Historical Building and Room Acoustics of the Stockholm Public Library (1925–28, 1931–32)

The Stockholm Public Library was realized in two distinct phases of construction in the 1920s and early 1930s, and remains a well-known work in twentieth-century architecture, with a heritage status today. While previous studies have focused on the library’s architectural design, particularly its lighting, acoustics were also an important aspect of the building’s design and construction. This study marks the first detailed investigation of the library’s architectural acoustics, with a suite of standard measurements performed to assess and characterize the library’s historical room and building acoustics. Reverberation time measurements in the library’s reading rooms yielded results of about 1.5–2 s for frequencies associated with speech. A significantly longer reverberation time of 5–6 s was measured in the library’s central rotunda, confirming a prominent acoustic issue in the library, where appropriate heritage discussions are needed in the future as the library undergoes a major renovation in the coming years. A comparison of the measured airborne and impact sound insulation of the 1920s and 1930s reading room ceilings also yielded interesting results. While the materials in library’s two construction periods are notably different, the airborne sound insulation performance of the 1920s and 1930s floors or ceilings was comparable and in line with contemporary standards. Impact sound insulation results from the 1920s and 1930s floors, however, differed significantly, with the latter displaying a relatively poor performance. Flanking transmission effects related to historical construction details and deviations from archival plans were investigated and discussed. This work emphasizes the practical and academic importance of conducting on-site measurements, and the close mutual development of modern architecture, construction, and architectural acoustics.

Optimal sensor placement for the spatial reconstruction of sound fields

The estimation sound fields over space is of interest in sound field control and analysis, spatial audio, room acoustics and virtual reality. Sound fields can be estimated from a number of measurements distributed over space yet this remains a challenging problem due to the large experimental effort required. In this work we investigate sensor distributions that are optimal to estimate sound fields. Such optimization is valuable as it can greatly reduce the number of measurements required. The sensor positions are optimized with respect to the parameters describing a sound field, or the pressure reconstructed at the area of interest, by finding the positions that minimize the Bayesian Cramér-Rao bound (BCRB). The optimized distributions are investigated in a numerical study as well as with measured room impulse responses. We observe a reduction in the number of measurements of approximately 50% when the sensor positions are optimized for reconstructing the sound field when compared with random distributions. The results indicate that optimizing the sensors positions is also valuable when the vector of parameters is sparse, specially compared with random sensor distributions, which are often adopted in sparse array processing in acoustics.

Optimizing Coziness and Productivity: An All-Encompassing Ergonomic Investigation on Diners and Restaurant Operators in Dense Urban Living Environments

This research aims to determine and optimize the welfare of visitors and food stall owners in dense urban environments, especially in the context of dense residential areas in big cities. As ergonomics research, its main focus is to assess the physical and psychological conditions of visitors and food stall owners operating in dense urban environments. This research method involves a detailed analysis of ergonomic aspects, including room layout, furniture design, lighting and acoustics, taking into account the unique demands of dense housing. In addition, in-depth interviews with food stall owners and observations of visitor behavior were conducted to understand the non-physical aspects that influence their well-being. The research location is in the Paseban area, Central Jakarta. The results of this research provide an in-depth understanding of how environmental conditions can influence comfort and productivity in food stalls, both from the perspective of visitors and owners. The practical implications of these findings can serve as a guide for architects, designers and policy makers in improving the design of public spaces in dense urban environments, with the ultimate goal of improving the welfare of local communities. This study makes a significant contribution to our understanding of how ergonomics can be applied effectively to improve the quality of life amidst the challenges of dense housing in large cities.

Enhanced Environmental Sustainability for the Acoustic Absorption Properties of Cabuya Fiber in Building Construction Using Machine Learning Predictive Model

Sustainability in construction is a growing concern due to the significant polluting waste generated before, during, and after a building’s life cycle. The use of natural materials can significantly reduce the environmental footprint in obtaining, manufacturing, transportation, execution, use, maintenance, and demolition of the building, especially when locally sourced. Natural fibers, in particular, can be used in room acoustics, offering good acoustic absorption while meeting sustainability goals. The objectives of this paper are to evaluate cabuya fiber, grown in Ecuador, as an acoustic absorbing material and to introduce a novel approach using machine learning to simulate the material’s acoustic properties. Eight samples of cabuya fiber, bound with a solution of water and Ca(OH)2, were prepared with thicknesses between 12 and 30.6 mm. The sound absorption coefficients (SACs) were calculated using an impedance tube, following international standards. A Gaussian regression model was built for the predictions. The results showed that the 30.6 mm sample achieved maximum absorption coefficients of 0.91 at 2 kHz and 0.9 at 5 kHz. The model predictions are very accurate, with a mean square error of just 0.0002. These findings offer valuable insights into using cabuya fiber and advanced predictive models to enhance building acoustic performance and reduce environmental impact.

A hybrid simulation approach to predicting noise in restaurants

High levels of noise are a well-known source of occupant discomfort in dining environments, and noise ranks highly among the most common customer complaints in restaurant reviews. Prior work has focused on measuring existing restaurant soundscapes and attempting to predict acoustic performance; however, current techniques are still limited in accuracy for restaurants with time-varying occupancy and complex layouts. This presentation demonstrates a novel approach to predicting ambient noise in restaurants via a hybrid simulation framework. Acoustical computations for a given restaurant space are performed in a room acoustics model, while a discrete event simulation (DES) model is used to simulate the arrival patterns of patrons and their conversational behaviors. Predictions from the room acoustics model inform the DES model, allowing for noise level predictions at each seat position. Results from the prediction model are validated against measurements in a case study restaurant. Further development of this framework may support the practical assessment of design interventions in any restaurant while also accounting for time-varying patterns of occupancy.

Time-dependent dynamical energy analysis via convolution quadrature

Dynamical Energy Analysis was introduced in 2009 as a novel method for predicting high-frequency acoustic and vibrational energy distributions in complex engineering structures. In this paper we introduce the first time-dependent Dynamical Energy Analysis method. Time-domain models are important in numerous applications including sound simulation in room acoustics, predicting shock-responses in structural mechanics and modelling electromagnetic scattering from conductors. The first step is to reformulate Dynamical Energy Analysis in the time-domain by means of a convolution integral operator. We are then able to employ the Convolution Quadrature method to provide a link between the previous frequency-domain implementations of Dynamical Energy Analysis and fully time-dependent solutions by means of the Z-transform. By combining a modified multistep Convolution Quadrature approach for the time discretisation, together with Galerkin and Petrov-Galerkin methods for the space and momentum discretisations, respectively, we are able to accurately track the propagation of high-frequency transient signals through phase-space. The implementation here is detailed for finite two-dimensional spatial domains and we demonstrate the versatility of our approach by performing a range of numerical experiments for regular, non-convex and irregular geometries as well as different types of wave source.

Statistical wave field theory.

In this paper, we introduce the foundations of the Statistical Wave Field Theory. This theory establishes the statistical laws of waves propagating in a closed bounded volume, that are mathematically implied by the boundary-value problem of the wave equation. These laws are derived from the Sturm-Liouville theory and the mathematical theory of dynamical billiards. They hold after many reflections on the boundary surface, and at high frequency. This is the first statistical theory of reverberation which provides the closed-form expression of the power distribution and the correlations of the wave field jointly over time, frequency, and space inside the bounded volume, in terms of the geometry and the specific admittance of its boundary surface. The Statistical Wave Field Theory may find applications in various science fields, including room acoustics, electromagnetic theory, and nuclear physics.

A rule-based framework for capturing geometric characteristics in design: A study of façade analysis for acoustic behaviour in urban space

In urban acoustics, the design of built environment substantially impacts the environmental noise of our everyday lives, as the built environment constantly reflects the sounds of human or non-human actors in its vicinity. The effects produced by these reflected sounds significantly depend on the geometric characteristics of the surrounding building façades. Despite their impact, the façade characteristics are often excluded from urban acoustic simulation models. As a result, sound reflection and scattering that are specifically related to building façades remain largely unexplored in noise control at the urban scale. Inspired by computational design tools used for exploring room acoustics, we investigate how a computational approach enables the analysis of geometric characteristics of façades to simulate urban acoustics during early design processes. This paper introduces a rule-based characterisation framework that enables the representation of geometric façade characteristics and their relationships with acoustic constraints in the form of rules. Our first results showed how these rules allowed for capturing and reconstructing façade geometries based on the given acoustic constraints. We believe that this novel approach empowers designers to describe their initial design ideas in a formalism that can be dynamically adapted to various dimensions, such as urban acoustics, and to reconstruct the form throughout the design process.

The link between the acoustic characteristics of worship spaces and their emotional impact.

The emotional impact of sound depends on its characteristics. Given that such characteristics can be modified when the sound is played in a room, it is crucial to examine how the acoustic characteristic of a room can impact the emotional experience. Researchers have investigated the links between the acoustic parameters of concert halls and the emotional impact; however, the applicability of such links to other building types, such as worship spaces, needs to be studied. In a previous study, the author analyzed the emotional response to the acoustic environments of worship spaces using self-report and physiological indicators. This paper builds on the previous work by analyzing the acoustic parameters of the buildings from the previous study and establishing links between such parameters and the emotional response indicators. It also analyzes the frequency domain to study the role of the interaction between the room and sound source in enhancing the emotional experience and introduces resonance quality (Q) and resonance width (Δf) as important parameters to consider in room acoustics. The results showed the significance of considering frequencies < 1000 Hz in analyzing the acoustics of the studied worship spaces and demonstrated that amplifying the dominant frequency range of the sound source was linked to enhancing the emotional experience.

Noise reduction in small wind turbines with optimized serrated blades

This study employs a comprehensive combination of experimental and numerical methodologies to delve into the aeroacoustic attributes of a small horizontal axis wind turbine with optimized blades. The experimental investigation is conducted within a semi-anechoic chamber, where both original and optimized geometry models are meticulously positioned to measure the sound pressure levels across a range of rotational speeds and positions. In parallel, the numerical simulations employed the large eddy simulation, complemented by the Ffowcs Williams–Hawkings analogy, facilitating detailed examinations of both aerodynamic and acoustic aspects in the original and optimized modes. The findings reveal a subtle enhancement in aerodynamic performance with the optimized serrated blade configuration when compared to the original. Nevertheless, the reduction in noise levels within the frequency domain was remarkable, culminating in an impressive overall sound pressure reduction of about 10 dB. Furthermore, an intriguing observation emerged from noise measurement in acoustic room: the noise production experiences a marked escalation as the turbine rotational speed intensifies, particularly within the downstream domain. The lateral noise level is found to be lower compared to the axial direction and the reduced noise emission for the serrated optimized blade is more dispersed in the plane of rotation than the original blade, which was pointed out to be nearly uniform. The results provide valuable insights into the interplay of aerodynamics and aeroacoustics in the context of small wind turbines with optimized blades.

Absorptive nature of scattering coefficients in stress-energy tensor formalism for room acoustics.

In the stress-energy tensor formalism, the symmetry between absorption and scattering coefficients, as proven by measurements combined with simulations, is counterintuitive. By introducing the wall admittance, we show that the scattering coefficient is partly created by the real part of the wall admittance combined with the active intensity, that is, is partly due to absorption. However, for curved surfaces or finite source distances, it also depends on the imaginary part of the wall admittance in combination with the reactive intensity, which confers its genuine scattering properties inversely proportional to the distances to the sources. Thus, for plane waves impinging on plane boundaries, or purely real admittances, scattering reduces to absorption.

An end-to-end approach for blindly rendering a virtual sound source in an audio augmented reality environment

Audio augmented reality (AAR), a prominent topic in the field of audio, requires understanding the listening environment of the user for rendering an authentic virtual auditory object. Reverberation time (RT60\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$RT_{60}$$\\end{document}) is a predominant metric for the characterization of room acoustics and numerous approaches have been proposed to estimate it blindly from a reverberant speech signal. However, a single RT60\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$RT_{60}$$\\end{document} value may not be sufficient to correctly describe and render the acoustics of a room. This contribution presents a method for the estimation of multiple room acoustic parameters required to render close-to-accurate room acoustics in an unknown environment. It is shown how these parameters can be estimated blindly using an audio transformer that can be deployed on a mobile device. Furthermore, the paper also discusses the use of the estimated room acoustic parameters to find a similar room from a dataset of real BRIRs that can be further used for rendering the virtual audio source. Additionally, a novel binaural room impulse response (BRIR) augmentation technique to overcome the limitation of inadequate data is proposed. Finally, the proposed method is validated perceptually by means of a listening test.

Mitigating Intensive Care Unit Noise: Design-Led Modeling Solutions, Calculated Acoustic Outcomes, and Cost Implications.

The study aimed to decrease noise levels in the ICU, anticipated to have adverse effects on both patients and staff, by implementing enhancements in acoustic design. Recognizing ICU noise as a significant disruptor of sleep and a potential hindrance to patient recovery, this study was conducted at a 40-bed ICU in Fiona Stanley Hospital in Perth, Australia. A comprehensive mixed-methods approach was employed, encompassing surveys, site analysis, and acoustic measurements. Survey data highlighted the importance of patient sleep quality, emphasizing the negative impact of noise on work performance, patient connection, and job satisfaction. Room acoustics analysis revealed noise levels ranging from 60 to 90 dB(A) in the presence of patients, surpassing sleep disruption criteria. Utilizing an iterative 3D design modeling process, the study simulated significant acoustic treatment upgrades. The design integrated effective acoustic treatments within patient rooms, aiming to reduce noise levels and minimize transmission to adjacent areas. Rigorous evaluation using industry-standard acoustic software highlights the design's efficacy in reducing noise transmission in particular. Additionally, cost implications were examined, comparing standard ICU construction with acoustically treated options for new construction and refurbishment projects. This study provides valuable insights into design-based solutions for addressing noise-related challenges in the ICU. While the focus is on improving the acoustic environment by reducing noise levels and minimizing transmission to adjacent areas. It is important to clarify that direct measurements of patient outcomes were not conducted. The potential impact of these solutions on health outcomes, particularly sleep quality, remains a crucial aspect for consideration.