Michael Vorlaender

• Dr
• Chair at RWTH Aachen University

Auralization of sound sources in outdoor spaces faces challenges not found in traditional room acoustics models. In particular, the late sound reflections and reverberation tail cannot be practically simulated by typical image source models or ray-tracing. Due to open regions in the outdoor geometries, the impulse responses are rather sparse. In ou...

The absorption and scattering coefficients of surfaces play a critical role in acoustic propagation simulations. However, the scattering coefficient defined by ISO 17497-1 is widely recognized as one of the most uncertain metrics in geometrical acoustics. In outdoor sound propagation simulations, the impulse response is typically sparse rather than...

Vehicle exterior noise is composed of speed-dependent contributions from tire/road interaction, powertrain, and aeroacoustic noise, each contributing to overall sound emission by characteristic directivity patterns. This work focuses on identifying the spatial and speed-dependent directivity patterns of a broad range of road-traffic vehicles (inclu...

Listening experiments are crucial for understanding human sound perception. In overall human perception, combined audiovisual effects play an important role. However, traditional virtual reality (VR) setups, consisting of a head-mounted display (HMD) and headphones, are limited by their need for expensive equipment and time-consuming laboratory ses...

Over the past decades, hearing aid technology has advanced considerably. Despite these advancements, hearing technology still faces limitations, leading to user dissatisfaction due to various factors. A frequently reported issue is an "unnatural" auditory experience when wearing hearing aids. This stems from the difference in acoustic behavior betw...

In order to examine the impact of different architectural features on sound source distance perception in future studies, the uncertainty of auralization results needs to be minimized and quantified. The RAVEN room acoustic software was benchmarked against measurements of the loudspeaker orchestra by Pätynen et al. in the Gasteig concert hall in Mu...

The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

Previous studies of the authors have shown that there are limitations when the existing acoustic energy models are applied to theatres. In the present study, a new semi-analytical model is developed based on site surveys and scale model measurements, aiming to overcome these limitations and provide a reliable prediction of the most relevant energy-...

The simulation of urban environments requires knowledge of vehicle directional noise emission characteristics to increase accuracy and provide more authenticity to 3D audio. This paper presents a methodology to extract the directional sound energy pattern emitted by a moving vehicle using a simple microphone array. The method involves recording the...

One of the major problems in the auralization of complex urban scenarios is the creation of ambience, i.e. the diffuse background which represents the sound floor on which the acoustic scene of interest is created. Omitting a realistic ambience results in a sterile and implausible impression. To overcome this drawback, a hybrid approach with admixt...

Building and room acoustics are relatively modern architectural and engineering disciplines, but acoustics have been a concern in buildings since ancient times, such as in Greek and Roman theatres. Today, we spend 80–90% of our time indoors, where sound significantly impacts our communication and actions, making it essential to consider acoustic as...

Transversely isotropic porous materials are well represented by equivalent fluid models based on semi-phenomenological models such as the Johnson-Champoux-Allard-Lafarge (JCAL) model and a set of material parameters. Direct measurements of these parameters, however, are often difficult or time consuming. As an alternative, inverse estimation method...

Deconvolution algorithms can considerably improve the spatial resolution of sound sources when applied to beamforming techniques. However, they are often associated with additional computation time, which can be prohibitive for real-time applications, especially when using high-resolution scanning grids. Additionally, depending on the size of the p...

Auralization has a key role in the design of immersive virtual reality tools for the study of human environments and their evolution. In soundscape and multisensory research, the validation of auralization frameworks traditionally relies on the impressions engendered by the virtual acoustic environment on the human subjects, and whether those impre...

Auralizations enable the simulation of sound fields in complex environments. For example, they can be used to investigate the perceptual aspects of sound emitted by vehicles. As input for the signal processing chain, sound source models must adequately represent the acoustic spatial and spectro-temporal characteristics of real vehicle emissions. An...

The IHTA at the RWTH Aachen University, Germany, opens its doors for a laboratory tour. It was founded in 1963 under the name ITA. The current directors of the institute are Michael Vorländer (since 1996) and Janina Fels (since 2012). In 2021, the institute was renamed the “Institute of Hearing Technology and Acoustics - IHTA” due to its expanded i...

Recent studies have provided valuable insight into the anatomy and motion of the cochlear partition, particularly emphasizing the flexible nature of the osseous spiral lamina (OSL). However, whether in studies involving air- or bone-conducted stimulation, the OSL is often treated as a rigid structure, overlooking its potential impact on the cochlea...

Auralizations are a valuable tool for demonstrating acoustic phenomena. They can form a basis on which both non-experts and experts can discuss and evaluate acoustic scenarios. However, creating auralizations often demands expert knowledge due to their complexity. The open-source, real-time auralization framework “Virtual Acoustics” (VA) aims to si...

The auralization of dynamic soundscapes brings significant computational challenges, as multiple often moving sources have to be considered simultaneously. Making such auralizations interactive rules out pre-rendering, requiring the underlying computations to be performed in real-time instead. The “Virtual Acoustics” (VA) framework allows for such...

In the field of urban design assessment, increasing attention to the nonexpert verbalizations is paid to engage social participation in planning processes, especially those not limited to static visual renderings. However, little has been explored on reproducible methods to collect these vocabularies and their relationship with architectural featur...

This paper presents a drone auralization model that reproduces the spectro-temporal and spatial characteristics of a drone during flight. Focusing on perceptual plausibility, the time-variant processes are modeled by taking into account the statistical amplitude and frequency modulation distributions of a reference drone sound. For completeness, th...

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 buildin...

Emerging technologies of virtual reality (VR) and augmented reality (AR) are enhancing soundscape research, potentially producing new insights by enabling controlled conditions while preserving the context of a virtual gestalt within the soundscape concept. This study explored the ecological validity of virtual environments for subjective evaluatio...

This paper presents a free-field method for inverse estimation of acoustic porous material parameters from sound pressure measurements above small rectangular samples. The finite sample effect, the spherical propagation of the sound field, and a potential lateral material reaction are considered. Using an extensive series of systematically varied f...

One of the major challenges in the auralization of complex urban simulations is the presence of ambience, for example background sounds. Omitting them can result in a sterile and implausible impression. In this work we present a dataset of spatially recorded ambient sounds with metadata on meteorological and acoustical parameters. The recordings ar...

The use of outdoor virtual scenarios promises to have a lot of potential to facilitate reproducible sensory evaluation experiments in laboratory. Auralizations allow for the integration of simulated or measured sound sources and transfer paths between the sources and receivers. Nonetheless, pure simulations can lack perfect plausibility. This contr...

Simulation of urban environments requires the knowledge of the vehicle directional noise emission characteristics, in order to be more accurate and confer more authenticity to the 3D audio. This paper presents a methodology to extract the directional sound energy pattern, emitted by a moving vehicle, using a simple microphone array. The method cons...

Urban noise pollution, particularly from road traffic, poses a significant challenge in modern cities. Simulation techniques have become crucial for designing and optimizing attractive, healthy living spaces. When it comes to more detailed analyses than required in standard noise mapping techniques, auralization, i.e. the creation of sounds in virt...

The acoustic far-field prediction of high-fidelity aerodynamic simulation data is still not accurately possible when accounting for the surface reflections from an aircraft’s fuselage or wings. By presenting a general method for order-reduced equivalent source modeling of aeroacoustic sound sources, this work is bridging the gap between high-fideli...

Auralization is a promising approach for future application in urban planning including noise aspects. From a technical point of view, auralization of the urban environment is challenging due to the high number of sound sources, time-variant and inhomogeneous atmospheric conditions and the large scale of scenarios. This work presents the modeling a...

The first edition of ISO 3382 was adopted in 1997. It already listed T30, Early Decay Time, Clarity, Definition, Center time, Lateral fraction and IACC as relevant room acoustic parameters. They are still up to date, only supplemented by the division into two dimensions of the spatial impression and by the stage support. In the last decade, new res...

A central part of auralization is the consideration of realistic sound propagation effects. This can be achieved using computationally efficient physics-based simulations based on the principle geometrical acoustics. When considering complex effects, e.g. curved propagation due to atmospheric refraction, those simulations can be computationally dem...

Virtuelle Akustik kann Personen auditiv in eine andere Umgebung versetzen, virtuelle Elemente zur realen Umgebung hinzufügen oder diese für den/die Nutzer:in modifiziert erscheinen lassen. Inzwischen erzielt die Virtuelle Akustik dabei perzeptiv so überzeugende Ergebnisse, dass sie sowohl als Werkzeug in der Forschung als auch als Technologie in ko...

The Helmholtz equation least-squares (HELS) method is a valuable tool for estimating equivalent sound sources of a radiating object. It solves an inverse problem by mapping measured pressures to a set of basis functions satisfying the Helmholtz equation in spherical coordinates. However, this problem is often ill-posed, necessitating additional reg...

Absorption and scattering coefficients of surfaces are crucial components of room-acoustic simulations. The random-incidence scattering coefficient is the most uncertain metric applied in geometrical acoustics. Databases of scattering coefficients are rare. Their impact on auditory perception in auralizations, however, is relatively well studied. R...

The occlusion effect (OE) denotes the increased low-frequency perception of bone-conducted sounds when the ear canal (EC) is occluded. Circuit and finite element (FE) models are commonly used to investigate the OE and improve its prediction, often applying acoustic impedances at the EC entrance and tympanic membrane (TM). This study investigates th...

Virtual Acoustics (VA) is the open-source real-time auralization framework developed at the Institute for Hearing Technology and Acoustics, RWTH Aachen University. Its modular structure allows the (real-time) auralization of various acoustic scenarios from simple free-field conditions to complex room acoustic and outdoor scenarios with dynamic sour...

The acoustic scattering of surfaces is crucial for acoustic simulations in rooms or urban spaces. The sound propagation is usually calculated by using geometrical simulation methods and random-incidence scattering coefficients. In a running project, new approaches towards angle-dependent scattering metrics are defined and investigated. With this, a...

The state-of-the-art models of soundscape planning and noise mapping are based on geometrical acoustics. Numerical wave models are possible but they exceed acceptable computation times for acoustics in practice by orders of magnitude. In geometrical acoustics, the sound is propagated either assuming Lambert’s diffusion or specular reflections, whic...

The introduction of the scattering coefficient has enabled geometrically-based acoustic simulations to produce full-length impulse responses of fairly high accuracy. However, the scattering coefficient is a random-incidence quantity that can be applied only when considering a statistical energy average over different directions. This model is inacc...

The software Virtual Acoustics (VA) is an open-source auralization framework developed at the Institute for Hearing Technology and Acoustics, RWTH Aachen University, Germany. Using physics-based models for source emission and sound propagation, it allows plausible rendering of virtual scenes based on purely synthetic data. Its modular design provid...

Measurements are essential for validating theories and making well-founded decisions. A criterion for the validity and comparability of measured values is their uncertainty. The latter aspect is not always applied in room acoustics. Using the standardized "Guide to the Expression of Uncertainty in Measurement" (GUM) framework, this contribution dis...

Today, there is a lack of standardized methods to study people’s perception of the architectural design of urban spaces. Moreover, outdoor spaces are subject to a continuous change of environmental conditions and variability of possible scenes. In order to conduct sensory evaluation experiments under reproducible conditions, it has been proposed to...

In acoustic array applications, it is important to know the sensor positions as precisely as possible in order to reduce the residual terms in the subsequent data processing. Depending on the mechanical design, especially with larger setups, the situation can arise, that the actually reached sensor positions are uncertain. In this contribution arra...

Within the research project "Person-focused Analysis of Architectural Design", it is a goal to correlate the individual soundscape attributes with objective urban space indicators. This contribution will present, in particular, a comparative analysis with the established Space Syntax indices, and more specifically, with isovists. These indices were...

This article presents an interactive system for stage acoustics experimentation including considerations for hearing one's own and others' instruments. The quality of real-time auralization systems for psychophysical experiments on music performance depends on the system's calibration and latency, among other factors (e.g. visuals, simulation metho...

Recent advances in the development of plausible environmental noise auralization tools are making way for their implementation in practical applications. In particular, increasingly realistic air traffic noise auralization frameworks are being developed. These could become powerful tools for assisting decision-making in architectural and urban plan...

p>Analysis of sound source directivity uncertainty for room acoustics simulations and auralizations. </p

As subsonic jets remain one of the major contributions to aircraft noise emissions, near-field flow simulations should be included in aircraft design at an early stage using quantitatively predicted sound pressure levels and the time-domain signal properties of the noise data. In this regard, the interface from the near-field data to the far-field...

Ultrasonic metal welding (USMW) is a welding technique often used in the electronic and automobile industries. However, the strength of the welds it produces is influenced by a large number of variables, making USMW difficult to monitor. There is therefore a need for monitoring parameters which can be used across a large number of influencing varia...

Absorption and scattering coefficients of surfaces are crucial for acoustic propagation simulations. The scattering coefficient according to ISO 17497-1, however, is the most uncertain standard metric applied in geometrical acoustics. In outdoor sound propagation simulation, the amount of scattered energy is crucial for the sound immission at the r...

p>Analysis of sound source directivity uncertainty for room acoustics simulations and auralizations. </p

Beamforming results depend on the spatial resolution of the microphone array used, which may lead to sources close to each other being considered as one. Deconvolution methods that consider all directions simultaneously, such as DAMAS, produce better results in these situations. However, they have a high computational cost, often lack sufficient sp...

The performance of singing, especially in religious context, is supposed to be strongly influenced by the room acoustic environment. The research project Sacred Sound - Sacred Space deals with the interaction of the environment and the performance and perception of singing in religious spaces. In this project, a technical setup has been created to...

Within the research project “Person-focused Analysis of Architectural Design”, it is a goal to elaborate a method which categorizes architectural design based on vocabulary describing audio-visual perception of built environments. The first step is to understand which dimensions are of importance to assess and verbalize the perception. Such a vocab...

The approach of auralization allows rendering plausible audio signals based on purely synthesized data. One key aspect for this is the simulation of sound propagation. Using sophisticated physics-based models, even complex situations—like sound propagation through an inhomogeneous, moving atmosphere—can be considered. However, even with fast approa...

The use of neural networks is becoming increasingly prevalent due to their ability to represent complex relationships and solve complex problems. However, implementing these models in systems that require low-latency output can be challenging, especially for practitioners who are used to developing their models in controlled environments like Pytho...

As part of the project Acoustics Knowledge Alliance (ASKnow), an online course including 30 lessons on the topic of acoustic simulations and auralization was created. It covers the required fundamentals of signal processing, gives an introduction into geometrical acoustics and wave-based simulation models for room acoustics, explains binaural synth...

Simulation models based on geometrical acoustics mostly do not immediately deliver a simulated room impulse response, but intermediate results such as an energy histogram or an energy decay curve. At this point, further models are required to generate a room impulse response of the simulated environment, which are essential for the process of aural...

Ultrasonic Metal Welding is a type of welding used in the production of electric car batteries. Currently, it suffers from quality fluctuations, and there is a need for online quality control techniques. One technique being investigated involves the measurement of the vibrations of the welding horn using laser vibrometry. However, this comes with t...

This work presents the procedure to create a model of the iconic scenery at Copacabana in Rio de Janeiro, Brazil, for auralization-based noise assessment in virtual urban environments with the aid of photogrammetry. The proposed procedure, firstly, delivers a description of the investigated space and of the photographic data acquisition. Secondly,...

Virtual reality offers attractive tools to assess the urban design and its consequences for the quality of life in cities, especially in complex acoustic scenarios. However, the evaluation with regard to the level of realism of such scenarios still is a challenge. In this study, individuals are assessing with their own words the realism of such ren...

Spatial fluctuations of room acoustic quantities in auditoria cast doubt on the validity of measurement results: when the measurement position is uncertain, the variation of the sound field over space can be understood as an influence factor affecting the overall (combined) uncertainty. This study presents a discussion consistent with the "Guide to...

This poster presents the IHTApark lab, a real environment monitorized with acoustic and visual recordings, as well as with weather indicators, together with a virtual reproduction of the same environment for real-time, realistic and physically-based renderings of such scenarios. The description in detail of how the virtual model has been designed a...

This work presents the design and implementation of a perceptionally plausible vehicle pass-by noise synthesis model for environmental noise auralization. The source model consists of two separate components for engine noise and road-tyre noise synthesis. Additionally, the model accounts for spatial radiation characteristics by including higher-ord...

When auralizing scenarios in the context of environmental noise, the simulation of sound propagation is an important aspect. Typically, the respective simulation models base on the concept of geometrical acoustics which enables processing a huge number of simulations even for complex scenes and higher frequencies in a reasonable time. However, the...

No PDF available ABSTRACT Recent comparisons of room-acoustic simulations and auralizations demonstrated that a high degree of realism can be achieved under certain conditions. How close the simulation can get to reality depends on the definition of the objective in general terms (authenticity or plausibility). The question is also what is the appl...

No PDF available ABSTRACT Absorption and scattering coefficients of surfaces are crucial components of room-acoustic simulations. The random-incidence scattering coefficient is the most uncertain metric applied in geometrical acoustics. Databases of scattering coefficients are rare. Their impact on auditory perception in auralizations, however, is...

Automated capturing of room models for acoustic simulation might reduce time when acquiring room geometries for acoustic simulations. Additionally, ecologically valid representations of rooms in terms of both modalities, audio and visuals, are required for a qualitative evaluation of sound in architectural contexts. Those requirements might be achi...

p>Analysis of sound source directivity uncertainty for room acoustics simulations and auralizations. </p

p>Analysis of sound source directivity uncertainty for room acoustics simulations and auralizations. </p

The ACOUCOU platform is a web-based, interactive, acoustics training platform that includes a set of free educational materials in various technical fields of acoustics. Educational materials are designed to serve as a modern self-development tool for students and engineers, as well as a comprehensive solution for professional education in the work...

Auralization is a suitable method for the subjective evaluation of environmental noise. Due to its complexity, the plausible and immersive acoustic representation of outdoor scenarios in urban environments is an ongoing field of research. This work presents the design and implementation of a vehicle pass-by noise model with application in a spatial...

In a recent publication, we presented an efficient method to find eigenrays in a stratified, moving medium. The simulation framework is designed to auralize aircraft flyovers. However, the method is restricted to the direct sound and a ground reflection. When dealing with flyover scenarios close to residential areas, the interaction of sound with u...

Urban planners and architects present their designs as the fittest best solution for open public demands. However, yet there is a big void significant gap between the promises of designers and how the public space is perceived, especially when including urban sound features. Even at a low level of detail, the interest for what people judge in such...

No PDF available ABSTRACT Measurements of random-incidence absorption coefficients have been hotly contested since the ASA was founded in 1929. Yes, you read correctly, since 1929! Theories, explanations, myths, and strange interpretations appear, disappear, and reappear over the decades. What is wrong with this method of measurement? This paper di...