The in situ measurement of acoustic surfaces presents a significant challenge in room acoustics, as it is often impractical to conduct laboratory measurements of already installed materials. In a former study, the in situ analysis of porous samples that react locally when supported by a solid wall demonstrated a good degree of accuracy. Nevertheless, when a porous layer is supported by a large air cavity (depth >100 mm), a situation commonly seen in suspended ceiling designs, the air cavity exhibits a non-locally reacting behavior; thus, the local reaction cannot be reliably assumed. This study introduces a method to characterize such a non-locally responding system through in situ PU probe measurements, utilizing an inverse technique to fit the parameters of the impedance model of a porous layer that is backed by an infinite air layer, based on the measured reflection coefficient. The precision of the approach was confirmed through 2D numerical simulations, indicating that the method produced reliable results for air cavities of 200 mm or deeper. The method was then experimentally validated on systems comprising several porous layers supported by air cavities of varying depths. Good agreement was obtained between the parameters measured experimentally using the proposed technique and the references, even in cases where the air cavity was less than 200 mm deep. Additionally, the proposed method demonstrated more precise characterization results compared to those achieved by fitting the parameters of an impedance model based on a standard multilayer model.

Ground vibrations generated by the operation of high-speed trains are one of the significant challenges at hand. These vibrations have the potential to cause harm to nearby structures through horizontal and vertical ground accelerations. A combination of sand crumb rubber (SCR) mixture and geofoam is explored as a vibration screening barrier parallel to the railway track. In the present study, train speeds of 80, 160, and 300 kmph were considered. A four-story building with a concrete frame structure near the railway track was simulated. Several parametric studies were conducted in this investigation. The variation in building acceleration at different floor levels caused by ground shaking from train-generated vibration was computed for various screening materials. There was an 8–10 dB vibration reduction after the trench, meaning that in areas with an excessive number of buildings, a combination of SCR and geofoam barriers might be placed parallel to the rail track.

As urbanization and building densities increase, the need for effective sound and thermal insulation in building design becomes increasingly important. This study investigates the impact of polypropylene fibers and microparticles on the sound and thermal insulation properties of recycled polyurethane foam. Microparticles with mesh sizes of 500, 750, and 1000 microns, along with polypropylene fibers under 1000 microns, were added to the recycled foam. Results indicate that thermal conductivity ranged from 0.07 to 0.15 W/(m²·K). The lowest thermal conductivity value (0.07 W/(m²·K)) was obtained in the sample containing recycled polyurethane foam with 5% by weight of polypropylene fibers, which provided the best thermal performance. Also, the Noise Reduction Coefficient (NRC)—as a standardized index for acoustic performance—was obtained in the range of 0.15–0.7. The highest NRC value was achieved by pure polypropylene fibers (0.70), followed by the sample containing recycled polyurethane foam reinforced with 3 wt% polypropylene microparticles sized 750–1000 µm (0.55). The results revealed that increasing the particle size generally improved NRC values, and increasing the polypropylene content up to 3 wt% enhanced the acoustic absorption performance, with further addition leading to diminishing returns. The addition of microparticles significantly improved sound absorption, with optimal particle sizes of 750–1000 microns yielding the best acoustic results, while the reinforced polypropylene fibers demonstrated the most effective thermal performance. Overall, these materials can provide effective solutions for enhancing building quality against sound and heat.

This research is aimed to quantify the extent of sound attenuation achievable through a slab formed by the Gosper structure. A metamaterial slab is designed using Gosper curve which are space coiling structures. The work also explores its potential applicability in creating quieter indoor environments, particularly in the context of creating acoustic barriers by stacking the slabs or making longer structures. The work proposes Peano-Gosper curve (PG), a space-filling and self-avoiding fractal that forms a hexagonal tiling pattern. These patterns were fabricated using concrete 3D printing techniques and evaluated for their sound attenuation. To investigate the sound attenuation capabilities of the Gosper structure, both experimental and numerical methods were employed. A harmonic excitation was applied as input to the structure, and sound transmission loss (STL) was calculated as a function of frequency. The experimental setup involved constructing a prototype slab of the Gosper structure created using additive manufacturing and subjecting it to controlled acoustic testing. Numerical simulations were carried out using finite element analysis, employing suitable material and boundary conditions to replicate real-world scenarios. The results obtained from the experimental and numerical analyses demonstrated a robust sound insulation capability by the single slab Gosper structure (28 dB). The findings suggest that the Gosper structure has the potential to serve as an effective multi-directional acoustic barrier in various architectural applications.

The acoustic properties of airlaid nonwoven panels made of Posidonia and Alfa natural fibers are compared to Hemp fibers. The acoustic performance of the panels is studied as a function of density and thickness. Experimental and modeling approaches are both considered. First, porosity and airflow resistivity are determined experimentally for several densities and compared with extrapolated values. This allows predicting the acoustic equivalent fluid properties for any density. Impedance tube measurements are then performed to determine the acoustical absorption coefficient. The equivalent fluid model, together with the extrapolated porosity and airflow resistivity for a given panel density, provides a good comparison with the measurements. The sound absorption properties of 0.04 and 0.08 m thick panels for densities of 40 and 80 kg/m 3 is finally compared for the three materials. We show that natural Posidonia and Alfa fibers have comparable efficiencies to Hemp fibers and can contribute to the development of more sustainable sound absorption materials.

Building regulations increasingly require balanced solutions for thermal comfort and acoustic performance, particularly for naturally ventilated dwellings. England’s Approved Document O (ADO) establishes noise thresholds for bedrooms using open windows for ventilation, allowing partially open windows (POW) rather than fully open ones to balance sound insulation with overheating mitigation. This study addresses the fundamental challenge of aligning acoustic and thermal modelling methodologies for POWs. Through field measurements at eight residential sites with diverse window configurations, we compared two assessment approaches: the theoretically-derived ‘Acoustic Open Area’ (AcOA) and the ventilation-based ‘Equivalent Area’ (EA). Statistical analysis revealed comparable accuracy between methods (standard deviations of 1.9 and 1.8 dB respectively), with no significant additional uncertainty when using EA instead of AcOA. Spectral analysis demonstrated that while measured sound insulation varies considerably with frequency, both methods effectively predict overall performance for typical environmental noise sources. This research establishes that EA – already used in thermal modelling – can reliably replace AcOA for acoustic assessments, significantly simplifying interdisciplinary coordination. These findings provide practical guidance for designers, engineers, and regulators developing integrated façade solutions that simultaneously address ventilation requirements and acoustic comfort.

The acoustic environment of schools is critical for effective learning, teaching, and wellbeing, with traditional guidelines prioritizing technical parameters such as noise levels thresholds, reverberation time, and sound insulation. However, the integration of soundscape principles, encompassing perceptual and experiential aspects of the auditory environment, remains underexplored. Gray literature offers a valuable resource for synthesizing reviews, particularly in fields where guidelines and policies are often published outside traditional academic channels. In this review a comprehensive gray literature search plan was developed using four complementary strategies: (1) gray literature databases, (2) customized Google search engines, (3) targeted website searches, and (4) consultation with field experts. Documents were screened for relevance through their abstracts, executive summaries, or tables of contents, followed by full-text reviews. Extracted data included acoustic parameters, user-centered elements, inclusion of wellbeing and soundscape considerations, and mentions of positive auditory stimuli. The search strategy identified 18 guidelines, most addressing traditional metrics like noise level thresholds and reverberation time. However, integration of soundscape principles, positive sounds, and wellbeing was minimal, with only 2 out of 18 guidelines (WELL Building Standard v2 and DQLS Version 3.0) mention soundscape principles, with WELL addressing auditory comfort and DQLS acknowledging natural sounds outdoors. User-specific needs were addressed in 11 guidelines, but user preferences were absent. Wellbeing was linked to acoustics in 6 guidelines, though mostly indirectly. These findings highlight gaps in addressing the experiential and psychological aspects of sound in educational environments.

A novel concept for enhancing timber floor slabs with integrated acoustic decoupling is introduced. The approach was evaluated through a series of measurements on both small-scale and large-scale setups. The tests involved a dual-shell timber slab system with discontinuous timber beam elements within the cavity. The timber beam elements are used to integrate acoustic decoupling into the structural system achieved through the use of targeted processing and geometric modification. The results show up to 5 dB improvement in the weighted normalized impact sound pressure level L n , w and the sound reduction index R compared to the unmodified reference system, without the addition of mass. This demonstrates the potential for improving sound insulation in lightweight timber structures, also in the low-frequency range, while maintaining minimal material use, offering significant implications for the design and construction of future building systems.

Mass timber panels are increasingly used in mass timber and hybrid construction projects for efficient off-site construction. Conventional continuous floating concrete toppings often struggle to achieve an apparent impact insulation class (AIIC) above 55 when tested according to ASTM standards. This study explores the impact sound insulation of raised discrete floating floor assemblies on cross-laminated timber (CLT) and dowel-laminated timber (DLT) floors through experimental testing. The study found that a raised discrete floating floor, constructed using commercially available dry materials such as oriented strand board (OSB), cement board, and gypsum board, significantly improved impact sound isolation and reduced the need for thick concrete layers. Interestingly, increasing the thickness of the floating concrete topping from 38 to 100 mm had minimal effect on sound insulation. Instead, cement boards provided an effective alternative, achieving an AIIC rating of 65 and offering a dry solution for improving sound insulation in timber construction.

This study focuses on the context of historiographical and acoustic research in St. Martin’s Cathedral in Bratislava, as it also serves as a concert hall. The aim of the study is to offer an innovative perspective on the interpretation of exact acoustic results in the context of concert productions. By applying heuristic research and acoustic field research according to the latest methodologies, it details the stages in the construction of the cathedral and characterizes its acoustic properties. The main contribution of the study lies in its detailed evaluation of the historico-cultural contexts and selected spatial acoustic parameters of the cathedral ( T 30 , T 20 , EDT, C 80 , IACC, BR ), together with recommendations for sound when concerts are held in it. Our acoustic research has revealed that St. Martin’s Cathedral is a suitable concert hall for specific instruments (organ, choral singing, wind and strings solo instruments). As for speech intelligibility without the use of sound reinforcement equipment ( STI ), it was found to be an unsatisfactory space.