Fatela: Interpolation of scheduled simulation results for auralization.
2022-06-02 09:15 - 10:15 (Europe/Berlin) | IHTA Seminarraum (60 Persons) and Zoom-Meeting (Hybrid), Kopernikusstr. 5, Aachen, 52074, Deutschland
Auralization is a technique which allows the rendering of realistic 3D audio based on virtual spatial scenes. Certain sound propagation parameters (or so-called auralization parameters) such as propagation delay, atmospheric attenuation, and spreading loss, can be derived from physics-based simulations of virtual scenes. These parameters are essential to rendering plausible sound signals in a spatial context. In the auralization of complex scenes, the simulations can be very computationally demanding. This can become a bottleneck for real-time auralization: The amount of resources required for the simulation must not compromise the real-time audio output. As a result, the simulations are run at a much lower rate than the audio rendering operations. Hence, sound propagation parameter values may „jitter“ over time, which can lead to audible artifacts in the output signal. This is especially true for the simulation of fast-moving sound sources, like aircraft, since parameters may change drastically in relatively small time intervals.
In this thesis, different methods are studied, tested, and implemented for the interpolation of sound propagation parameters in the context of aircraft flyovers. This is thought to be an elegant solution to both upsample and smooth out the auralization parameter data with the goal of avoiding audible artifacts in real-time auralization.
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Zoom-Meeting-ID: 914 7471 2584
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Kahle: The Concert Hall - a machine for music? Or how to integrate acoustic design into architecture
2022-06-03 11:00 - 12:00
For Concert Halls, most people agree that the acoustic quality is a quintessential element of the success of the project, and often the acoustics is considered as being more important than the architectural design. Yet it should be clear that architecture and acoustics are totally interwoven, and every architectural decision will have an acoustic effect and vice versa. Even the dimensions of interest are the same in acoustics and architecture, the wavelengths of audible sound range from a few millimeters (corresponding to architectural surface texture) to a few meters (corresponding to large-scale architectural design). At Kahle Acoustics, we believe that acoustic solutions should not be “bolted on” but integrated into the architectural language. The advantage is that, once the acoustic principles are clear and taken into account, there are always several solutions to achieve the goals and the most appropriate solution can be developed in close collaboration with the architects.
Examples will be given ranging from Concert Hall design, where the architectural freedom is very different between a shoebox design and a vineyard or free-form design, to placement of absorption in offices, restaurants and auditoria.
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Zoom-Meeting-ID: 975 1497 5390
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Stienen: Real-time auralisation of outdoor sound propagation
2022-06-03 13:00 - 14:00
Auralisation describes the process of generating and presenting audible sound using computer programs and audio hardware. Since the result is perceived naturally by the human’s auditory system, a demonstration by means of auralisation is easily comprehensible and does neither require background knowledge nor expertise. Producing auralisation under real-time constraints increases the implementation demands significantly. Real-time auralisation is required in applications that respond to user interaction, for example, in interactive Virtual Reality (VR) environments. Dynamically moving sound sources and receivers evoke a change in the perceived sound, and the corresponding result must be provided as quickly as possible. A feeling of immersion can be created if the response time of the system does not exceed perceptual thresholds and thus enables a plausible scene presentation. To achieve this emotional state, real-time auralisation must comply with the expected physical behaviour.
The realisation of a real-time auralisation application for outdoor environments represents a promising addition to current noise assessment procedures. It also delivers the foundation for the auditory modality in outdoor VR scenarios, which can server as as an audio-video tool for perception-related scientific investigations.
In the past, auralisation has gained much attention in room acoustics. An attempt to transfer the established concepts and approaches to outdoor environments reveals two systemic deficiencies.
Firstly, room acoustic simulations are commonly based on Geometrical Acoustics (GA), which determines reflected sound rapidly and with high accuracy, but struggles to incorporate diffracted sound. In most urban settings, however, the transmission of sound from a noise source to a receiver contains a significant contribution of both reflected and diffracted components. Furthermore, dynamic virtual environments are time-variant. Traditional realisations often neglect this characteristic, treating an acoustic environment as temporarily static on a frame-by-frame basis. Adaption to dynamic events is implemented by transition of sequences of time-invariant simulations, which is contradictory to the highly dynamic nature of outdoor scenarios.
To address these two misconceptions, a real-time auralisation system is suggested that attaches increased importance to fast geometric diffraction simulations and is based on an audio rendering network that reflects the time-variant nature of dynamic outdoor sound propagation.
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Zoom-Meeting-ID: 910 1346 5160
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Zusammenfassung in deutscher Sprache:
Echtzeit-Auralisierung von Außenlärm-Szenarien
Auralisierung beschreibt den Prozess der Erzeugung und Präsentation hörbaren Schalls mittels Computerprogrammen und Audio-Hardware. Weil das Resultat durch den menschlichen Hörapparat auf natürlichem Wege wahrgenommen wird, ist eine Demonstration durch Auralisierung unmittelbar verständlich und benötigt weder Hintergrundwissen noch Erfahrung. Eine solche Auralisierung unter Echtzeitbedingungen durchzuführen erhöht die Anforderungen an die Implementierung
beträchtlich. Echtzeit-Auralisierung wird in Anwendungen benötigt, die auf Benutzereingaben reagieren, zum Beispiel, in interaktiven Umgebungen der Virtuellen Realität (VR). Sowohl dynamische, bewegte Schallquellen als auch Empfängerbewegungen rufen eine Änderung des wahrgenommenen Schalls hervor und erfordern, dass eine entsprechende Anpassung so schnell wie möglich bereitgestellt wird. Das Gefühl der Immersion kann erzeugt werden, wenn die
Reaktionszeit des Systems perzeptive Schwellen unterschreitet und die Präsentation plausibel erscheint. Um diesen emotionalen Status zu erreichen, muss Echtzeit-Auralisierung mit dem erwarteten, physikalischen Verhalten übereinstimmen.
In der Vergangenheit hat die Auralisierung viel Aufmerksamkeit im Bereich der Raumakustik erfahren. Der Versuch, die etablierten Verfahren auf Außenlärm-Szenarien zu übertragen weist zwei systemische Defizite auf. Zum einen basieren Raumakustik-Simulationen üblicherweise auf dem Prinzip der Geometrischen Akustik (GA), welche zwar reflektierten Schall schnell und präzise bestimmen kann, jedoch erheblichen Mehraufwand bei der Integration von gebeugtem Schall benötigt. In vielen urbanen Situationen besteht die Lärmimission allerdings zu einem maßgeblichen Anteil aus reflektiertem und gebeugtem Schall. Darüber hinaus sind dynamische virtuelle Umgebungen zeitabhängig. Traditionelle Realisierungen vernachlässigen diesen Aspekt und behandeln eine virtuelle Umgebung als Zeitfolge, bei der jeder Abschnitt kurzzeitig als stationär erachtet wird. Die Adaption dynamischer Ereignisse erfolgt dann mittels Überblendungen dieser Sequenzen von zeitinvarianten Simulationen, welche den Grundsatz einer hochdynamischen Außenlärm-Situation nicht widerspiegelt.
Um diesem widersprüchlichen Ansatz zu begegnen wird ein Echtzeit-Auralisierungssystem vorgestellt, welches einerseits der schnellen Beugungssimulation gesteigerte Wichtigkeit beimisst und andererseits auf einem Netzwerk digitaler Audio-Verarbeitungseinheiten basiert, das die zeitvariante Natur von Schallereignissen in üblichen Außenlärm-Situationen berücksichtigt.

Ercandogu: Process state estimation in ultrasonic metal welding from airborne sound recordings
2022-06-09 09:00 - 09:30
Ultrasonic metal welding is a solid-state bonding process in which metal workpieces are
exposed to high-frequency vibrations. It is an effective joining technology with a wide range
of industrial applications with its unique advantages. The vibrations of mechanical parts in
the machine cause fluctuations in the air pressure, thus causing sound waves to radiate. The
radiating sound may be directly related to the component vibrations. As a result, changes
in the process can be monitored by detecting changes in the airborne sound. This thesis
aims to study the airborne sound radiated during ultrasonic metal welding and estimate the
relation between the sound and the process stages. Several features are examined to achieve
this goal, starting with frequency analysis. The spectrogram of the airborne sound shows
that the sound emitted has a mostly constant amplitude and contains many frequencies,
most notably the fundamental frequency and its harmonics. These frequencies are examined
in relation to time in order to define transitions between different stages. Additionally, a
relationship between the welding strength and the welding frequency is investigated but no
correlation was discovered. Two ratios are derived to measure nonlinearity, one comparing
the fundamental frequency with all other frequencies, and the other with its harmonics. The
analysis presents comprehensive tables showing the relationship between welding stages and
the studied features. It is evident from the tables that there is a correlation between the
frequency behaviors and the stages of the process.
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Zoom-Meeting-ID: 967 6798 9931
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Lu: Vibration transfer function between horn and anvil measurements in ultrasonic metal welding
2022-06-09 09:30 - 10:00
Ultrasonic Metal Welding (USMW) is a quite important welding technique, because of the relative low heat this welding process generate, it is used in numerous industrial applications. However, this welding technique have a disadvantage, the welding strength have large variance despite the same values of input machine parameters. Thus, to improve this welding technique more knowledge about welding process is required.
In this thesis the data sets are 44 measurements on the oscillation of the horn and anvil vibrations along the direction of USMW between two copper layer sheets recorded by Laser Doppler vibrometers (LDV). Based on the model suggested by Balz, this work derives a mechanical model of the welding process, and uses it to estimate the spring and damping coefficients of the weld at different parts of welding. The estimation of the relationship of amplitude and phase shift between horn and work pieces is based on record of high-speed camera filtered at 20kHz. After prepossessing, the 44 measurements are being fitted into mass-spring-damper model using slight window method. Finally, the relationship between frequency and spring-damper coefficient will be analyzed.
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Seitz: Intentional switching of spatial auditory selective attention in preschool children
2022-06-17 11:00 - 12:00
From the beginning of their auditory development, children are immediately confronted with the challenge of orienting themselves in complex acoustic situations. Whether a parent’s voice or a passing vehicle, it is crucial to distinguish an auditory signal from the acoustic environment. Spatially distributed sound sources, distracting sounds, and disturbing background noise, for example, impede this listening process. The ability to focus on the relevant target source while blocking out simultaneous distracting sounds in a multi-layered acoustic environment is known as auditory selective attention or the cocktail party effect. In everyday communication situations, people can shift attention from one target sound to another, such as when children are called by their parents while talking to another child. Therefore, children also develop the ability to intentionally switch their auditory selective attention from one sound source to another. At the Institute of Hearing Technology and Acoustics in Aachen, a paradigm was developed to study the intentional switching of auditory selective attention in children. It considers spatial reproduction and background noise. This thesis extended the paradigm to examine the ability of intentional switching in auditory selective attention in preschool children aged three to six years. For this purpose, a listening experiment with ninety-one children (3-6 years, 47.25 % female) was conducted in several day-care centers in Aachen. The research hypothesis was that the ability of intentional switching in auditory selective attention matures between the ages of three and six. In addition, the extent to which background noise as well as different spatial sound source distributions influence this intentional attention switching were examined. Differences in response time between age groups were found, in particular a significant decrease in response time between three- and five-year-olds. This is thought to be due to termination of myelination of the brain stem’s radiations to the auditory cortex at age five. It has been confirmed that children are affected by background noise. Surprisingly, this was reflected in a decrease in response times for experiment parts with noise compared to those without. Possible reasons for this could be a noise avoidance strategy or an increase in attention caused by noise. It was revealed that children could not use less complex spatial sound source distributions to their benefit, which is probably related to the still ongoing myelination of the connection between the two cerebral hemispheres that lasts into the teenage years. The investigation of the suitability of the paradigm for three- to six-year-old children showed that the paradigm is appropriate for four- to six-year-olds. More than half of the three-year-olds were not able to successfully complete the introduction tasks, which is why only a conditional suitability of the paradigm was determined for this age group.

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Zoom-Meeting-ID: 959 5601 6670
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Domah: Categorisation of urban soundscapes under variable weather conditions
2022-06-24 11:00 - 11:30
The IHTA park is used as a case study for a lot of the institute´s research on auralisation and visualisation of urban scenes. An audio-visual model of the park already exists, which uses synthesised sounds for the dominant technical transportation sounds, while inserting recorded sounds as background sounds. Hence, a database of recorded background sounds made in the IHTA park is necessary. Unfortunately, the recordings of existing database cannot be used for auralisation, as they are oftentimes uncalibrated and lack ambient indicators of the outdoor settings. When reproducing the specific scene, however, it is crucial to include the ambient weather parameters of the collected audio data. This is especially true when analysing the IHTA park under variable weather conditions, since meteorological factors have a significant effect on both the outdoor sound propagation as well as the acoustical and visual perception on the receiver-end. By coherently matching the audio data and with corresponding meteorological data, the IHTA park can be reproduced with increased ecological validity. Therefore, the goal of this thesis is to create a database of audio recordings under variable weather conditions and include the meteorological and ambient data for the corresponding scene.
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Zoom-Meeting-ID: 954 6079 3355
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Yang: Unsicherheiten der Quellparameterschätzung aus PKW-Vorbeifahrtgeräuschen
2022-06-24 11:30 - 12:00
Die Hörbarmachung urbaner Lärmszenarien mittels Außenlärm-Auralisationen ist neben geeigneten Modellen zur Simulation von Schallausbreitung- und empfängern angewiesen auf Modelle von bewegten Quellen wie beispielsweise PKW. In dieser Arbeit wird die Unsicherheit der Quellparameterschätzung von Vorbeifahrtgeräuschen der Fahrzeuge untersucht. Dazu werden die realen Richtcharakteristiken des Mikrofons analysiert. Außerdem werden die Auswirkungen unsicherer Parameter bei der Berechnung der Schallausbreitungsdämpfung durch Monte-Carlo-Simulationen und Sensitivitätsanalysen untersucht.
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Wenzel: The influence of varying degree of visualization on spatial audio-visual congruency effects with short-term memory performance
2022-06-28 10:30 - 11:30
When understanding and recalling spoken language, various complex processes take place in the brain. Certain circumstances can either impede or facilitate speech comprehension, e.g. visual stimuli such as lip movements or gestures. Although the field of cognitive psychology has already intensively studied short-term memory performance or listening effort in such situations, it mostly uses simple scenarios without plausible visual and auditory material. It is therefore possible that the performance of participants in such studies differs from reality.
This work investigates spatial congruency effects, i.e., the performance of the subjects depending on whether the perceived direction from which the acoustic signal comes is congruent with the direction in which a source is visually located. The established serial-recall paradigm is used, which allows the evaluation of short-term memory performance. As a further variable, a 3D-virtual reality (VR) environment is compared to an acoustic laboratory environment with single screens.
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Zoom-Meeting-ID: 919 9972 3349
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Zhu: Examining the influence of visual stimuli on auditory selective attention in a virtual classroom
2022-06-28 11:30 - 12:00
Auditory selective attention (ASA) is a common phenomenon which describes the ability to intentionally focus on a specific source of sound while ignoring other irrelevant sounds. Since in real life there are usually visual distractors in addition to auditory distractors, the effect of visual stimuli on ASA is also worth investigating. The purpose of this study was to explore a new paradigm to investigate the influence of visual stimuli on ASA. In addition, the experiment was carried out in a virtual reality classroom because using virtual reality for research allows for the simulation of a variety of complex scenarios without changing the laboratory environment. The listening experiment was conducted with 24 adults. The statistical analysis revealed that the presence or absence of visual stimuli had a significant effect on reaction times and error rates of ASA, and the congruence of the visual stimulus compared to the auditory target stimulus also showed a trend to an effect which was not significant. Further investigations are needed to investigate this phenomenon and refine the audiovisual paradigm if necessary.
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