Stephan Werner

Communication technologies play an important role in maintaining the grandparent-grandchild (GP-GC) relationship. Based on Media Richness Theory, this study investigates the frequency of use (RQ1) and perceived quality (RQ2) of established media as well as the potential use of selected innovative media (RQ3) in GP-GC relationships with a particular focus on digital media. A cross-sectional online survey and vignette experiment were conducted in February 2021 among N = 286 university students in Germany (mean age 23 years, 57% female) who reported on the direct and mediated communication with their grandparents. In addition to face-to-face interactions, non-digital and digital established media (such as telephone, texting, video conferencing) and innovative digital media, namely augmented reality (AR)-based and social robot-based communication technologies, were covered. Face-to-face and phone communication occurred most frequently in GP-GC relationships: 85% of participants reported them taking place at least a few times per year (RQ1). Non-digital established media were associated with higher perceived communication quality than digital established media (RQ2). Innovative digital media received less favorable quality evaluations than established media. Participants expressed doubts regarding the technology competence of their grandparents, but still met innovative media with high expectations regarding improved communication quality (RQ3). Richer media, such as video conferencing or AR, do not automatically lead to better perceived communication quality, while leaner media, such as letters or text messages, can provide rich communication experiences. More research is needed to fully understand and systematically improve the utility, usability, and joy of use of different digital communication technologies employed in GP-GC relationships.

The paper presents an alternative approach for estimating reverberation time from measurements in real rooms when the requirements of the standard DIN EN ISO 3382-1/2 for the characteristics of the sound source, receiver, and measurement positions cannot be met. The main goal is to minimize the variance of the calculated reverberation times when using a directional source and receiver, or source-receiver relative positions with very small distances. For this purpose, the energy decay curve for individual octave bands is sampled in time. The estimation starts 2 ms after the direct sound. This is followed by several estimates of the RT over a 20 dB drop, starting 1 dB later with each iteration. The best fit mean of these values gives the estimated reverberation time. A comparison with the standard reverberation time estimation shows a variance reduction of 10% to 30% for binaural room impulse responses (BRIRs). The proposed method finds its application in situations where measurements can only be made at a few positions in the room and/or only in a few areas of the room. Furthermore, the method should be better suitable for measurements with receivers located near or at the head of a person.

In the field of Auditory Augmented Reality (AAR), one aim is to provide a listening experience that is as close as possible to a real scenario. Measured Spatial Room Impulse Responses (SRIRs) describe the acoustics of a room and can serve as a reference for acoustic simulations or parametrization of room acoustics. In previous works, a measurement system for SRIRs using a mobile robotic platform was introduced. The system consists of a commercially available self-driving platform on which a microphone array is mounted, while the sound sources are distributed at fixed positions in the room. The system is able to conduct high spatial resolution measurements of SRIRs in a uniform grid. In applications where time is limited and/or the area to discover is large, however, a high-resolution measurement is not always feasible.Therefore, the goal of this contribution is to compare different approaches for optimizing the measurement grid. One approach is to use mathematical optimization on acoustic parameters derived from a small set of initial measurements to determine new measurement positions in a iterative manner. Another approach is to optimize the measurement grid in respect to human auditory perception, incorporating e.g. just-noticeable differences of distance and localization perception.The results show that both approaches can achieve significant reductions in the number of measurements required for a adequate acoustic spatial reproduction, with different trade-offs depending on the application scenario and the available prior information.

How humans perceive, recognize, and remember room acoustics is of particular interest in the domain of spatial audio. For the creation of virtual or augmented acoustic environments, a room acoustic impression matches the expectations of certain room classes or a specific room. These expectations are based on the auditory memory of the acoustic room impression. In this paper, the authors present an exploratory study to evaluate the ability of listeners to recognize room acoustic features. The task of the listeners was to detect the reference room in a modified ABX double-blind stimulus test that featured a pre-defined playback order and a fixed time schedule. Furthermore, the authors explored distraction effects by employing additional nonacoustic interferences. The results show a significant decrease of the auditory memory capacity within 10 s, which is more pronounced when the listeners were distracted. However, the results suggest that auditory memory depends on what auditory cues are available.

To achieve the goal of a perceptual fusion between the auralization of virtual audio objects in the room acoustics of a real listening room, an adequate adaptation of the virtual acoustics to the real room acoustics is necessary. The challenges are to describe the acoustics of different rooms by suitable parameters, to classify different rooms, and to evoke a similar auditory perception between acoustically similar rooms. An approach is presented to classify rooms based on measured BRIRs using statistical methods and to select best match BRIRs from the dataset to auralize audio objects in a new room. The results show that it is possible to separate rooms based on their room acoustic properties, that the separation also corresponds to a large extent to the perceptual distance between rooms, and that a selection of best match BRIRs is possible.

Background: Loneliness and social isolation in older age are considered major public health concerns and research on technology-based solutions is growing rapidly. This scoping review of reviews aims to summarize the communication technologies (CTs) (review question RQ1), theoretical frameworks (RQ2), study designs (RQ3), and positive effects of technology use (RQ4) present in the research field. Methods: A comprehensive multi-disciplinary, multi-database literature search was conducted. Identified reviews were analyzed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) framework. A total of N = 28 research reviews that cover 248 primary studies spanning 50 years were included. Results: The majority of the included reviews addressed general internet and computer use (82% each) (RQ1). Of the 28 reviews, only one (4%) worked with a theoretical framework (RQ2) and 26 (93%) covered primary studies with quantitative-experimental designs (RQ3). The positive effects of technology use were shown in 55% of the outcome measures for loneliness and 44% of the outcome measures for social isolation (RQ4). Conclusion: While research reviews show that CTs can reduce loneliness and social isolation in older people, causal evidence is limited and insights on innovative technologies such as augmented reality systems are scarce.

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.

The aim of auditory augmented reality is to create an auditory illusion combining virtual audio objects and scenarios with the perceived real acoustic surrounding. A suitable system like position-dynamic binaural synthesis is needed to minimize perceptual conflicts with the perceived real world. The needed binaural room impulse responses (BRIRs) have to fit the acoustics of the listening room. One approach to minimize the large number of BRIRs for all source-receiver relations is the synthesis of BRIRs using only one measurement in the listening room. The focus of the paper is the evaluation of the spatial audio quality. In most conditions differences in direct-to-reverberant-energy ratio between a reference and the synthesis is below the just noticeable difference. Furthermore, small differences are found for perceived overall difference, distance, and direction perception. Perceived externalization is comparable to the usage of measured BRIRs. Challenges are detected to synthesize more further away sources from a source position that is more close to the listening positions.

Spatial audio processing includes recording, modification and rendering of multichannel audio. In all these fields there is the choice of either a physical representation or of perceptual approaches trying to achieve a target perceived audio quality. Classical microphone techniques on one hand and wave field synthesis, higher order ambisonics or certain methods of binaural rendering for headphone reproduction on the other hand target a good physical representation of sound. As it is known today, especially in the case of sound reproduction a faithful physical recreation of the sound wave forms ("correct signal at the ear drums") is neither necessary nor does it allow a fully authentic or even plausible reproduction of sound. 20 years ago, MPEG-4 standardized different modes for perception based versus physics based reproduction (called "Perceptual approach to modify natural source" and "Acoustic properties for physical based audio rendering"). In spatial rendering today, more and more the perceptual approach is used in state of the art systems. We give some examples of such rendering. The same distinction of physics based versus psychoacoustics (including cognitive effects) based rendering is used today for room simulation or artificial reverb systems. Perceptual aspects are at the heart of audio signal processing today.

Diese Arbeit umfasst meine Forschungstätigkeiten auf dem Gebiet des räumlichen Hörens. Es wird der Frage nachgegangen, welche Effekte verschiedene Kontexteinflüsse auf die Herausbildung einer auditorischen Illusion haben. Diese Effekte werden quantitativ erfasst. Es werden die Wahrnehmung von Externalität, Hörereignisrichtung u. a. bei Verwendung eines Binauralsynthesesystems untersucht. Als Ziel steht die Beschreibung und Messbarmachung der Kontexteinflüsse Raumdivergenz, Personalisierung und visuelle Merkmale. Die eigenen Untersuchungen zeigen deutlich, dass für das Zustandekommen einer sogenannten perfekten auditorischen Illusion eine ausreichende technische Realisierung der korrekten Ohrsignale nicht ausreichend ist. Vielmehr ist eine Erfüllung der intrinsischen Erwartungshaltung des Hörers notwendig. Der Prozess der Herausbildung von Qualität lässt sich durch einen Vergleich und Beurteilungsprozess beschreiben. Hierbei werden die aus den durch die Sinnesorgane aufgenommenen Reizungen abgeleiteten Qualitätsmerkmale mit den abgeleiteten Merkmalen einer inneren, individuellen Referenz verglichen. Dieser Prozess ist ausschlaggebend für die Herausbildung eines Hörereignisses. Mithilfe von qualitätsbewertenden Befragungen (Hörtests) lässt sich dieses Hörereignis als Abbildung messbar und beschreibbar machen. Die Ergebnisse meiner Arbeit zeigen, dass eine Divergenz akustischer Raumparameter zwischen einer binaural synthetisierten Szene und dem Abhörraum zu einer signifikanten Verringerung der Externalisierung von Hörereignissen führt. Eine Konvergenz raumakustischer Parameter erhöht die wahrgenommene Externalisierung. Die Sichtbarkeit von bspw. Lautsprecherattrappen im Abhörraum lässt die Externalität insgesamt ansteigen. Der sogenannte Raumdivergenzeffekt kann dadurch aber nicht aufgelöst werden. Die Personalisierung eines Binauralsynthesesystems zeigt eine Verringerung von Fehllokalisationen und einen Anstieg der Externalisierung. Es wird die Vermutung aufgestellt und untersucht, inwiefern Lokalisierungsfehler und Externalisierung korrelieren. Es wird gezeigt werden, dass eine personalisierte Binauralsynthese den Raumdivergenzeffekt nicht auflösen kann. Die Untersuchungen zum Raumdivergenzeffekt dienen als Grundlage zur Entwicklung von Methoden, welche verschiedene zeit- und energiebasierte akustische Merkmale der verwendeten Raumimpulsantworten verändern. Das Ziel ist die Anpassung einzelner raumakustischer Parameter der Synthese an die Raumakustik des Abhörraumes zur Erzeugung einer plausiblen auditorischen Illusion.

This contribution presents investigations on the influence of scene complexity and room acoustic disparity on the perception of different quality features using a binaural headphone system. The quality features "spatial presence" and "listener envelopment" are investigated next to "perceived externalization" and "localization" of an auditory event. The test uses three different rooms with distinct room acoustic characteristics and several scenes with different spatial complexity. The work addresses the question if the quality features can profit by the different audio scenes or not. The results show that spatial presence is influenced by spatial complexity while room acoustic disparity influences listener envelopment. Furthermore, externalization and localization are not affected by spatial complexity regardless of the personalization method used for binaural synthesis.

The auditory system of humans enables the perception of spatial audio in real and virtual acoustics using monaural and binaural cues. The perception of direction and distance are two prominent quality features to evaluate the quality of experience of spatial audio systems. Inaccuracies in perception can occur if physical quality elements of the synthesis system are not adequate. In this study a binaural synthesis via headphones is used to re-synthesize single sound sources on several discrete positions on a full circle around the listener. An artificial head (KEMAR) and a two channel spherical microphone setup are used to measure binaural room impulse responses in a real environment. A listening test is performed to measure the number of quadrant errors and perceived externalization of the auditory events in a localization task. The distributions of its frequencies depending on the direction of the re-synthesized sound source are investigated. The results show a continuous relationship between the investigated quality features and the direction of the sound source. Furthermore, an analysis of the relationship between quadrant errors and externalization depending on direction and used binaural room impulse responses are presented.

The development of recording and playback systems is motivated by the goal to create a perfect auditory illusion. In the last decades audio systems like ambisonics, wave field synthesis and binaural headphone reproduction gained in importance. Efforts are made to increase the quality of such systems. Despite the years of research and development, there are still many perceptual effects and psychoacoustical factors which are still unknown or not fully understood. This contribution presents a research project which deals with the systematically analysis of perceptual effects regarding to binaural playback. Based on the results of listening tests a measurement model on the perception of binaural synthesized scenes is developed. For this, a set of quality features needs to be determined and evaluated. These quality features and their weightings can be summarized as plausibility of perception. The plausibility of a binaural auralization does not only depend on physical quality elements of the synthesis system, but also depends significantly on contextual factors. During the project several different auditive scenes are created for evaluation. The contextual factors which influence the quality features are varied. Different rooms for playback and recording are considered as well as variations of the complexity of the acoustical scene, the degree of personalization and the type of visual presentation. Dependencies between these factors are expected and are going to be evaluated. This contribution presents first results of contextual factors influencing quality features.

Beyond the correct technical realization of binaural signals and synthesis, perceptional effects depending on congruence and divergence between the synthesized scene and listening situation have a not neglectable influence on perception and plausibility of synthesis. This contribution deals with the perceived externalization and plausibility of virtual acoustic environment at binaural headphone synthesis. Investigations of divergence and congruence between listening room and auralized room are conducted. The Direct-to-Reverberant-energy-Ratio (DRR) as an adjustable parameter of binaural room impulse responses is adapted to evaluate externalization and perceived congruence between the synthesized scene and the listening environment. A clear influence of the listening room on perception of externality is visible in the results of the listening tests.

It is well-known that the perception of the position of audio and video stimuli is not independent. In general, video dominates the position if the position offset between audio and video is small. Most previous work focused on natural listening conditions and position offsets between audio and video in the horizontal plane. There is little research concerning offsets in vertical direction and artificial, auralized sound environments. Among different approaches to auralization of spatial audio, the binaural reproduction is especially very interestingas it offers proper perception of direction, distance, and elevation of sound sources at moderate cost. This article addresses the question whether the thresholds of perceptual fusion of audio and video stimuli are the same in binaural reproduction systems and in natural listening conditions. To estimate the influence of audio-visual discrepancy on vertical sound source localization, two experiments have been designed. The test methods were optimized to improve usability and minimize rating errors. Both experiments resulted in psychometric functions of intersensory bias for competing audio and visual stimuli. For binaural reproduction, the obtained results showed an effect of similar magnitude for both the vertical and horizontal plane which is in good agreement with the results obtained from other studies in natural environments.

Die meisten derzeitigen binauralen Wiedergabesysteme werden mit Kopfhörern realisiert. Dabei können aber Phänomene wie eine Im-Kopf-Lokalisation und eine Vorne-Hinten-Konfusion auftreten und der Entfernungseindruck kann verloren gehen. Aus diesen Gründen wurde die Wiedergabe mit Lautsprechern in einer Stereoanordnung untersucht. Das Wiedergabesystem wurde als statisch angenommen, d.h. zusätzlich zur Stereoanordnung sind die Abhörposition und die horizontale und vertikale Ausrichtung des Kopfes bekannt. Bei einer normalen Stereowiedergabe kommt es zu einem Übersprechen zwischen dem linken Lautsprecher und rechten Ohr und umgekehrt. Deshalb wurde ein Übersprechkompensator realisiert und im Wiedergabesystem implementiert. Zusätzlich zur Realisierung der Übersprechkompensation werden die Einflüsse des Mess- und Wiedergaberaumes kompensiert. Um sich von früheren Untersuchungen zu unterscheiden, wird die Wiedergabe nicht unter Freifeld- sondern unter Diffusfeldbedingungen durchgeführt.