Traditionally, the management of environmental noise was focused mainly on measuring the physical parameters of the acoustic environment, as defined by international standards. However, over the years, several studies have shown that reducing sound pressure levels not always leads to an improvement in quality of life. Consequently, a new perspective on this problem has been emerging, called the “soundscape” approach, which also incorporates users’ perception and contextual factors in this evaluation. Since the UNESCO Convention for the Safeguarding of the Intangible Cultural Heritage, in 2003, there has been a growing interest in the analysis of soundscapes in places of high cultural significance, recognizing the need to preserve the acoustic environment as it contributes to the identity of a place and influences the visitor’s experience. In this study, the soundscape of historical areas of high heritage value, located in the urban zone of Coimbra, Portugal, was analysed, applying the soundwalk methodology, according to the ISO/TS 12913. The acoustic environment is described by means of appropriate acoustic indicators; however, it does not incorporate psychoacoustic parameters. The findings suggest that this comprehensive approach is essential for fully understanding the sound environment of a place, as sound pressure levels alone are insufficient to explain acoustic perception, since the type and characteristics of sound sources significantly affect how environments with similar LAeq values are experienced. ​

While increased sound levels near the ground in downwind conditions are a well-studied topic, comparatively little attention has been given in the literature to increased sound pressure levels in upwind propagation. This increase, however, typically occurs only under specific conditions, including an elevated source location, a non-linear (e.g., logarithmic) wind or temperature profile, and a focus on particular distances within the upwind domain. These conditions are known to be responsible for the formation of caustics. Simultaneously, the sound level enhancement may be disturbed by diffraction, ground reflection, and its characteristics depend on the source structure, being most readily derivable for point sources. Consequently, investigations using models and comparisons with observations are challenging. This work uses two fundamentally different modelling approaches in their ability to capture such phenomena. The goal is to provide an intuitive understanding of the complex interactions involved in sound propagation under real atmospheric conditions, thereby supporting the interpretation of acoustic simulation and measurements in applied contexts.

Laboratory experiments in psychoacoustical and soundscape research indicate that participants perceive a reproduction sound level lowered by 8-10 dB as more plausible than the original level. This bias supposedly roots in an adaptation of perceptual loudness scaling to the laboratory environment, that is overall quieter than urban outdoor soundscapes. To gain further insights into the nature of such loudness bias, we conducted a listening experiment in both field and laboratory using a within-subjects design. Thirty-one participants visited a street and listened to the environmental sounds for one minute, while these sounds were also recorded using a dummy head. Thereafter, they listened to the recording in a quiet laboratory nearby and adjusted its level as they remembered it. About half of the sample did this immediately, the other half about 20 minutes after the recording. Results confirm a bias towards lower levels with a mean of about 8.9 dB, regardless of the time between the recording and the reproduction in the laboratory. Also, participants with higher musical abilities tended to select higher, more accurate levels, whereas noise-sensitive participants deemed lower levels appropriate. Results suggest that the hypothesized adaptation of perceptual scaling to the laboratory happens immediately and is affected by individual factors.

The Laboratoire Vibrations Acoustique is a research unit of INSA Lyon, founded in the late 1960s to study vibrations and their consequences on noise emitted by machines and structures. The aim of this article is to review the history and main developments of the laboratory over the last fifty years. After examining the early years of the laboratory, we retrace the developments and key scientific contributions that have enabled it to gain renown at national and international levels in the field of vibration and acoustical engineering.

Auralization of outdoor sound propagation has become an important tool for studying noise perception in the contexts of aircraft, wind farm, and drone noise. To achieve high realism, these auralizations consider amplitude fluctuations caused by atmospheric turbulence. In a recent publication, a semi-empirical model was introduced which is applicable to relatively long outdoor sound propagation such as aircraft and wind farm noise, as it considers the saturation effect for amplitude fluctuations in the partially-saturated regime. This article presents a study applying the semi-empirical model for investigating the impact of turbulence-induced amplitude fluctuations on annoyance in auralized aircraft flyovers. For this, two 2-alternative-forced-choice listening experiments were conducted in a controlled laboratory setting: the first tested whether participants could reliably detect audible differences between aircraft flyovers under different meteorological conditions; the second assessed which condition was perceived as more annoying. The results show that strong differences in meteorological conditions and the respective atmospheric turbulence can lead to salient audible differences. Relative annoyance ratings tend to increase with stronger atmospheric turbulence. Further, the data suggest that amplitude fluctuations can interact with other characteristics of aircraft noise such as fan tones and alter the perceptual impact of these characteristics. Therefore, the study highlights the importance of modeling turbulence-induced amplitude fluctuations in realistic aircraft auralizations, and presumably also wind farm and drone noise auralization, as the perceptual impression can be affected in several ways.

This paper outlines the history and activities related to acoustics in Slovakia during the 20th century, focusing specifically on the Faculty of Civil Engineering at Slovak Technical University (STU) in Bratislava. The research in acoustics is presented within a historical context that has been notably turbulent in the Central European region. Consequently, the article examines the research and education in acoustics separately for the period before 1989 and the period following the fall of communism. It shows how the development of acoustics as a scientific discipline has been influenced by historical, political, and economic factors, particularly by several waves of emigration from Slovakia to Western EU and North America. The article is based on accessible information in the university library, historical research performance, testimonies of retired professors and colleagues, visits to university archives, and the archives of the Catholic Church. Finally, this paper presents recent research activities at STU Bratislava, the largest and best technical university in Slovakia, within national and European frameworks. It outlines the focus of scientific work and education for future architects, civil engineers, and material scientists.

The prediction and modeling of sound propagation rely heavily on accurate representations of surface scattering. Traditional scattering coefficients, often based on random-incidence assumptions, fail to capture the directional dependence of sound reflections from rough surfaces. This paper introduces a methodology for determining and representing bidirectional surface scattering coefficients, moving beyond the limitations of existing Lambertian-based approaches. We propose a framework that leverages numerical simulations and physical measurements to compute bidirectional scattering coefficients from reflected sound pressure distributions with finite-size samples. The methodology is validated using a well-documented sinusoidal test surface, comparing our results with analytical solutions for infinite-size samples and former random-incidence scattering coefficient measurements. Additionally, we propose a data storage format compatible with the Spatially Oriented Format for Acoustics (SOFA) to facilitate the integration of bidirectional scattering coefficients into sound propagation models. This work provides a foundation for improved acoustic simulations in applications ranging from room acoustics to urban noise control.

Prediction of the acoustic performance of 3D printed materials is investigated at normal and grazing incidence. A direct numerical (microscopic) simulation that solves the full set of Navier–Stokes equations is used as a reference. It is compared with a macroscopic approach in which the material is represented by an equivalent fluid. The materials have a periodic microstructure, consisting either of a single network of spherical or cubic cavities connected by cylindrical channels or of a double-nested network. The samples are printed using the stereolithography technique and are tested using an impedance tube and a duct test bench. For single network geometries, the results of sound absorption at normal and grazing incidence predicted using the equivalent fluid approach are in good agreement with those obtained by the microscopic approach. Comparisons with impedance tube measurements confirm that both approaches can accurately predict the absorption coefficient of the samples. For the in-duct liner configuration, the transmission loss measurements and predictions show similar evolution with frequency change, despite the discrepancy in amplitude. For the double network geometry, the equivalent fluid approach cannot exactly reproduce the results obtained with the direct numerical simulation. Finally, while the predictions with the microscopic approach provide a good match with the impedance tube measurements, only a poor agreement is obtained using the duct testing bench.

Outdoor noise measurement is highly uncertain due to its strong dependence on environmental conditions. In firearm noise studies, these uncertainties are amplified by the impulsive nature of the noise and the lack of large datasets, making long-term meteorological averaging and stochastic techniques impractical. Numerical models also face limitations, with most commercial software relying on coefficient-based environmental predictions. This study investigates uncertainties and environmental effects in outdoor firearm noise propagation, combining experimental and numerical approaches to understand their impacts. The expanded uncertainty of systematic (Type B) uncertainties contribute up to ±4.1 [dB], while random (Type A) uncertainties, influenced by environmental variability, range from ±0.5 to ±10 [dB], predominantly affecting mid- to high-frequency bands at extended distances. A refined 2D Nonlinear Progressive Equation (NPE) model is used to simulate varying terrains and atmospheric conditions. Results reveal that sound-dampening terrains, such as grass, cause significant amplitude and spectral shifts compared to asphalt, with attenuations up to 10 [dB] at specific frequencies and distances. Downwind conditions enhance high-frequency propagation, while upwind scenarios reduce signal strength, with notable effects indicatively happening beyond 65 [m]. The findings highlight the importance of environmental characterization and advanced modeling as complementary tools for understanding and contextualizing uncertainties in firearm noise studies, supporting the development of improved methodologies for military and civilian acoustic applications.

Acoustic comfort is an important factor that passengers and crew usually consider for their on-board wellness. The classification is an efficient way to show the level of acoustic comfort on board. Most of the existing classification approaches of on-board noise in different spaces are based on the decibel based indicators which describes the loudness. However, acoustic comfort is not only relevant to decibel based indicators but also perceptual attributes such as timbre and pitch. In order to provide more perceptual support, a satisfaction based classification method for acoustic comfort is modified, determining the limits of the noise in different task-oriented spaces on board. Perceptual assessments were carried out to obtain numerical values for acoustic comfort as noise comfort index (NCI) and measured satisfaction (SM) of each noise sample. Analysis made on these two descriptors indicated that the NCI has a strong relationship with SM. Therefore, satisfaction can be regarded as a basic perceptual guideline to classify the acoustic comfort and determine the limits of each level for each task-oriented space. A linear acoustic comfort model was established to predict the NCI based on the acoustic parameters. Comparison with the previous classification of on-board noise showed that there is a mismatch between the NCI and sound pressure level (SPL), and NCI can not be fully represented by SPL.