On the plausibility of simplified acoustic room representations for listener translation in dynamic binaural auralizations. - Ilmenau : Universitätsbibliothek, 2023. - 1 Online-Ressource (167 Seiten)
Technische Universität Ilmenau, Dissertation 2023
Diese Doktorarbeit untersucht die Wahrnehmung vereinfachter akustischer Raumrepräsentationen in positionsdynamischer Binauralwiedergabe für die Hörertranslation. Die dynamische Binauralsynthese ist eine Audiowiedergabemethode zur Erzeugung räumlicher auditiver Illusionen über Kopfhörer für virtuelle, erweiterte und gemischte Realität (VR/AR/MR). Dabei ist es nun eine typische Anforderung, immersive Inhalte in sechs Freiheitsgraden (6DOF) zu erkunden. Dynamische binaurale Schallfeldimitationen mit hoher physikalischer Genauigkeit zu realisieren, ist meist mit sehr hohem Rechenaufwand verbunden. Frühere psychoakustische Studien weisen jedoch darauf hin, dass Menschen eine begrenzte Empfindlichkeit gegenüber den Details des Schallfelds haben, insbesondere im späten Nachhall. Dies birgt das Potential physikalischer Vereinfachungen bei der positionsdynamischen Auralisation von Räumen. Beispielsweise wurden Konzepte vorgeschlagen, die auf der perzeptiven Mixing Time oder der Hörbarkeitsschwelle von frühen Reflexionen basieren, für welche jedoch eine gründliche psychoakustische Bewertung noch aussteht. Zunächst wurde ein Aufbau zur positionsdynamischen Raumauralisation implementiert und evaluiert. Daran untersucht die Arbeit wesentliche Systemparameter wie die erforderliche räumliche Auflösung eines Positionsrasters für die dynamische Anpassung. Da allgemein etablierte Testmethoden zur wahrnehmungsbezogenen Bewertung von räumlichen auditiven Illusionen unter Berücksichtigung interaktiver Hörertranslation fehlten, untersucht die Arbeit verschiedene Ansätze zur Messung der Plausibilität. Auf dieser Grundlage werden physikalische Vereinfachungen im Verlauf des Schallfeldes in positionsdynamischen binauralen Auralisationen der Raumakustik untersucht. Für die Hauptexperimente wurden binaurale Raumimpulsantworten (BRIRs) entlang einer Linie für die Hörertranslation in einem eher trockenen Hörlabor und einem halligen Seminarraum ähnlicher Größe gemessen. Die erstellten Datensätze enthalten Szenarien von Hörerbewegungen auf eine virtuelle Schallquelle zu, daran vorbei, davon weg oder dahinter. Darüber hinaus betrachten die Untersuchungen zwei Extremfälle der Quellenorientierung, um die Auswirkungen einer Variation der Schallquellenrichtcharakteristik zu berücksichtigen. Die BRIR-Sätze werden systematisch bearbeitet und vereinfacht, um die Auswirkungen auf die Wahrnehmung zu bewerten. Insbesondere das Konzept der perzeptiven Mixing Time und manipulierte räumlich-zeitliche Muster früher Reflexionen dienten als Testfälle in den psychoakustischen Studien. Die Ergebnisse zeigen ein hohes Potential für Vereinfachungen, unterstreichen aber auch die Relevanz der genauen Imitation prominenter früher Reflexionen. Die Ergebnisse bestätigen auch das Konzept der wahrnehmungsbezogenen Mixing Time für die betrachteten Fälle der positionsdynamischen binauralen Wiedergabe. Die Beobachtungen verdeutlichen, dass gängige Testszenarien für Auralisierungen, Interpolation und Extrapolation nicht kritisch genug sind, um allgemeine Schlussfolgerungen über die Eignung der getesteten Rendering-Ansätze zu ziehen. Die Arbeit zeigt Lösungsansätze auf.
https://doi.org/10.22032/dbt.57596
Proof-of-concept study to evaluate the impact of spatial audio on social presence and user behavior in multi-modal VR communication. - In: IMX 2023, (2023), S. 209-215
This paper presents a proof-of-concept study conducted to analyze the effect of simple diotic vs. spatial, position-dynamic binaural synthesis on social presence in VR, in comparison with face-to-face communication in the real world, for a sample two-party scenario. A conversational task with shared visual reference was realized. The collected data includes questionnaires for direct assessment, tracking data, and audio and video recordings of the individual participants’ sessions for indirect evaluation. While tendencies for improvements with binaural over diotic presentation can be observed, no significant difference in social presence was found for the considered scenario. The gestural analysis revealed that participants used the same amount and type of gestures in face-to-face as in VR, highlighting the importance of non-verbal behavior in communication. As part of the research, an end-to-end framework for conducting communication studies and analysis has been developed.
https://doi.org/10.1145/3573381.3596458
Plausibility of an approaching motion towards a virtual sound source II: in a reverberant seminar room. - In: AES Europe Spring 2022, (2022), S. 559-571
This study investigates the plausibility of dynamic binaural audio scenarios wherein the listener interactively walks towards a virtual sound source. An originally measured BRIR set was manipulated and simplified systematically to challenge plausibility, explore its limits, and examine the relevance of selected acoustic properties. After the first investigation in a quite dry listening laboratory, this second exploratory study repeats and extends the experiment in a considerably more reverberant room. The participants had to rate externalization, continuity, stability of the apparent sound source, impression of walking towards the sound source and the plausibility of the virtual acoustic scene. The results confirm the observations of the first study in the different acoustic environment. Both studies indicate much room for simplifications, but certain modifications seriously affect plausibility. Even inexperienced listeners notice if the progress of the auditory distance change does not match their own walking motion. In addition, the meaning of context and expectation for the perception of binaural audio is highlighted.
Discriminability of concurrent virtual and real sound sources in an augmented audio scenario. - In: AES Europe Spring 2022, (2022), S. 521-529
This exploratory study investigates peoples’ ability to discriminate between real and virtual sound sources in a position-dynamic headphone based augmented audio scene. For this purpose, an acoustic scene was created consisting of two loudspeakers at different positions in a small seminar room. Considering the presence of headphones, non-individualized BRIRs measured along a line with a dummy head wearing AKG K1000 headphones were used to allow for head rotation and translation. In a psychoacoustic experiment, participants had to explore the acoustic scene and tell which sound source they believe is real or virtual. The test cases included a dialog scenario, stereo pop-music and one person speaking while the other speaker played mono-music simultaneously. Results show that the participants were on trend able to debunk individual virtual sources. However, for the cases where both sound sources reproduced sound simultaneously, lower distinguishability rates were observed.
Augmented/mixed reality audio for hearables: sensing, control, and rendering. - In: IEEE signal processing magazine, ISSN 1558-0792, Bd. 39 (2022), 3, S. 63-89
Augmented or mixed reality (AR/MR) is emerging as one of the key technologies in the future of computing. Audio cues are critical for maintaining a high degree of realism, social connection, and spatial awareness for various AR/MR applications, such as education and training, gaming, remote work, and virtual social gatherings to transport the user to an alternate world called the metaverse. Motivated by a wide variety of AR/MR listening experiences delivered over hearables, this article systematically reviews the integration of fundamental and advanced signal processing techniques for AR/MR audio to equip researchers and engineers in the signal processing community for the next wave of AR/MR.
https://doi.org/10.1109/MSP.2021.3110108
Perceptual matching of room acoustics for auditory augmented reality in small rooms - literature review and theoretical framework. - In: Trends in hearing, ISSN 2331-2165, Bd. 26 (2022), S. 1-22
For the realization of auditory augmented reality (AAR), it is important that the room acoustical properties of the virtual elements are perceived in agreement with the acoustics of the actual environment. This perceptual matching of room acoustics is the subject reviewed in this paper. Realizations of AAR that fulfill the listeners? expectations were achieved based on pre-characterization of the room acoustics, for example, by measuring acoustic impulse responses or creating detailed room models for acoustic simulations. For future applications, the goal is to realize an online adaptation in (close to) real-time. Perfect physical matching is hard to achieve with these practical constraints. For this reason, an understanding of the essential psychoacoustic cues is of interest and will help to explore options for simplifications. This paper reviews a broad selection of previous studies and derives a theoretical framework to examine possibilities for psychoacoustical optimization of room acoustical matching.
https://doi.org/10.1177/23312165221092919
The availability of a hidden real reference affects the plausibility of position-dynamic auditory AR. - In: Frontiers in virtual reality, ISSN 2673-4192, Bd. 2 (2021), 678875, S. 1-17
This study examines the plausibility of Auditory Augmented Reality (AAR) realized with position-dynamic binaural synthesis over headphones. An established method to evaluate the plausibility of AAR asks participants to decide whether they are listening to the virtual or real version of the sound object. To date, this method has only been used to evaluate AAR systems for seated listeners. The AAR realization examined in this study instead allows listeners to turn to arbitrary directions and walk towards, past, and away from a real loudspeaker that reproduced sound only virtually. The experiment was conducted in two parts. In the first part, the subjects were asked whether they are listening to the real or the virtual version, not knowing that it was always the virtual version. In the second part, the real versions of the scenes where the loudspeaker actually reproduced sound were added. Two different source positions, three different test stimuli, and two different sound levels were considered. Seventeen volunteers, including five experts, participated. In the first part, none of the participants noticed that the virtual reproduction was active throughout the different test scenes. The inexperienced listeners tended to accept the virtual reproduction as real, while experts distributed their answers approximately equally. In the second part, experts could identify the virtual version quite reliably. For inexperienced listeners, the individual results varied enormously. Since the presence of the headphones influences the perception of the real sound field, this shadowing effect had to be considered in the creation of the virtual sound source as well. This requirement still limits test methods considering the real version in its ecological validity. Although the results indicate that the availability of a hidden real reference leads to a more critical evaluation, it is crucial to be aware that the presence of the headphones slightly distorts the reference. This issue seems more vital to the plausibility estimates achieved with this evaluation method than the increased freedom in motion.
https://doi.org/10.3389/frvir.2021.678875
Comparing the effect of different open headphone models on the perception of a real sound source. - In: 150th Audio Engineering Society Convention 2021, (2021), S. 389-398
Creation of auditory augmented reality using a position-dynamic binaural synthesis system - technical components, psychoacoustic needs, and perceptual evaluation. - In: Applied Sciences, ISSN 2076-3417, Bd. 11 (2021), 3, 1150, S. 1-20
For a spatial audio reproduction in the context of augmented reality, a position-dynamic binaural synthesis system can be used to synthesize the ear signals for a moving listener. The goal is the fusion of the auditory perception of the virtual audio objects with the real listening environment. Such a system has several components, each of which help to enable a plausible auditory simulation. For each possible position of the listener in the room, a set of binaural room impulse responses (BRIRs) congruent with the expected auditory environment is required to avoid room divergence effects. Adequate and efficient approaches are methods to synthesize new BRIRs using very few measurements of the listening room. The required spatial resolution of the BRIR positions can be estimated by spatial auditory perception thresholds. Retrieving and processing the tracking data of the listener’s head-pose and position as well as convolving BRIRs with an audio signal needs to be done in real-time. This contribution presents work done by the authors including several technical components of such a system in detail. It shows how the single components are affected by psychoacoustics. Furthermore, the paper also discusses the perceptive effect by means of listening tests demonstrating the appropriateness of the approaches.
https://doi.org/10.3390/app11031150
Minimum BRIR grid resolution for interactive position changes in dynamic binaural synthesis. - In: 148th Audio Engineering Society International Convention 2020, (2020), S. 660-669