Perceived quality and spatial impression of room reverberation in VR reproduction from measured images and acoustics. - In: Proceedings of the 23rd International Congress on Acoustics, (2019), S. 3361-3368
https://edocs.tib.eu/files/e01mr19/1677542403.pdf
Perceptual aspects in spatial audio processing. - In: Proceedings of the 23rd International Congress on Acoustics, (2019), S. 3354-3360
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.
https://edocs.tib.eu/files/e01mr19/1677542403.pdf
Data set: BRIRs for position-dynamic binaural synthesis measured in two rooms. - In: Audio for virtual, augmented and mixed realities, (2019), S. 165-169
Binaural room impulse responses were measured with a KEMAR 45BA head-and-torso-simulator. For the first data set, it was placed at different positions located on a line with a length of 2 m in a 25 cm positional resolution and an azimuth resolution of 4˚. Two source positions were considered in the setup, one in front of the line, one at the side. The same arrangement of source and receiver positions was realized in two different rooms, a quite dry listening laboratory and a quite reverberant seminar room. For the second data set, BRIRs and omni-directional RIRs were measured for a translation line with a length of 7.5 m through the given seminar room. The data sets are valuable for realizing, testing and studying dynamic binaural walk-through scenarios in the two different rooms.
https://doi.org/10.22032/dbt.39972
Real-time estimation of reverberation time for selection of suitable binaural room impulse responses. - In: Audio for virtual, augmented and mixed realities, (2019), S. 145-150
The aim of auditory augmented reality is to create a highly immersive and plausible auditory illusion combining virtual audio objects and scenarios with the real acoustic surrounding. For this use case it is necessary to estimate the acoustics of the current room. A mismatch between real and simulated acoustics will easily be detected by the listener and will probably lead to In-head localization or an unrealistic acoustic envelopment of the virtual sound sources. This publication investigates State-of-the-Art algorithms for blind reverberation time estimation which are commonly used for speech enhancement algorithms or speech dereverberation and applies them to binaural ear signals. The outcome of these algorithms can be used to select the most appropriate room out of a room database for example. A room database could include pre-measured or simulated binaural room impulse responses which could directly be used to realize a binaural reproduction. First results show promising results combined with low computational effort. Further strategies for enhancing the used method are proposed in order to create a more precise reverberation time estimation.
https://doi.org/10.22032/dbt.39968
Investigation on spatial auditory perception using non-uniform spatial distribution of binaural room impulse responses. - In: Audio for virtual, augmented and mixed realities, (2019), S. 137-144
For spatial audio reproduction in the context of virtual and augmented reality, a position-dynamic binaural synthesis can be used to reproduce the ear signals for a moving listener. A set of binaural room impulse responses (BRIRs) is required for each possible position of the listener in the room. The required spatial resolution of the BRIR positions can be estimated by spatial auditory perception thresholds. If the resolution is too low, jumps in perception of direction and distance and coloration effects occur. This contribution presents an evaluation of spatial audio quality using different spatial resolutions of the position of the used BRIRs. The evaluation is performed with a moving listener. The test persons evaluate any abnormalities in the spatial audio quality. The result is a comparison of the quality and the spatial resolution of the various conditions used.
https://doi.org/10.22032/dbt.39967
Audio for virtual, augmented and mixed realities : proceedings of ICSA 2019 : 5th International Conference on Spatial Audio, September 26th to 28th, 2019, Ilmenau, Germany. - Ilmenau : ilmedia, 2019. - 1 Online-Ressource (vii, 186 Seiten)
https://doi.org/10.22032/dbt.39936
Das VR-Headset als digitaler Kanal : Limitationen der heutigen VR-Technik für das Digital Storytelling erkennen und intelligent vermeiden. - In: FKT, ISSN 1430-9947, Bd. 73 (2019), 10, S. 45-50
Quality assessment of spherical microphone array auralizations. - Ilmenau : Universitätsbibliothek, 2019. - 1 Online-Ressource (viii, 214 Seiten)
Technische Universität Ilmenau, Dissertation 2019
Die vorliegende Arbeit beschäftigt sich mit der Qualitätsbewertung und -vorhersage in virtuellen akustischen Umgebungen, insbesondere in Raumsimulationen basierend auf Kugelarraydaten, die mithilfe binauraler Synthese auralisiert werden. Dabei werden verschiedene Prädiktionsverfahren angewandt, um den Einfluss des Arrays auf die Wiedergabequalität automatisiert vorherzusagen, indem die Daten von Hörexperimenten mit denen eines auditorischen Modells in Bezug gesetzt werden. Im Fokus der Experimente stehen unterschiedliche, praxisrelevante Aspekte des Messsystems, die einen Einfluss auf die Wiedergabequalität haben. Konkret sind dies Messfehler, wie räumliches Aliasing, Rauschen oder Mikrofonpositionierungsfehler, oder die Konfiguration des Arrays. Diese definiert das räumliche Auflösungsvermögen und entspricht der gewählten Ordnung der Sphärischen Harmonischen Zerlegung. Die Experimente basieren auf Kugelarray-Simulationen unter Freifeldbedingungen und in einfachen simulierten Rechteckräumen mit unterschiedlichen Reflexionseigenschaften, wobei ein Raum trocken, der andere dagegen stark reflektierend ist. Dabei dienen zehn Testsignale als Audiomaterial, die in praktischen Anwendungen relevant erscheinen, wie z. B. Orchester- oder Popmusik, männlicher und weiblicher Gesang oder Kastagnetten. In Wahrnehmungsexperimenten wird der Einfluss von Messfehlern in einer quantitativen Analyse bewertet und die Qualität der Synthese deskriptiv mit den Attributen Apparent Source Width (ASW) und Listener Envelopment (LEV) bewertet. Die resultierenden Daten bilden die Basis für die Qualitätsvorhersage, wobei die Hörtestergebnisse als Observationen und die Ausgangsdaten des auditorischen Modells als Prädiktoren dienen. Mit den Daten werden unterschiedliche Prädiktionsmodelle trainiert und deren Vorhersagegenauigkeit anschließend bewertet. Die entwickelten Modelle ermöglichen es, sowohl Messfehler zu identifizieren und zu klassifizieren als auch deren Ausprägung zu schätzen. Darüber hinaus erlauben sie es, den Einfluss der Arraykonfiguration auf die Wahrnehmung von ASW und LEV vorherzusagen und die verwendete Ordnung der Schallfeldzerlegung zu identifizieren, ebenso wie die Reflexionseigenschaften des simulierten Raumes. Es kommen sowohl einfache Regressionsmodelle und Entscheidungsbäume zur Anwendung als auch komplexere Modelle, wie Support Vector Machines oder neuronale Netze. Die entwickelten Modelle zeigen in der Regel eine hohe Genauigkeit bei der Qualitätsvorhersage und erlauben so die Analyse von grundlegenden Array-Eigenschaften, ohne aufwendige Hörexperimente durchführen zu müssen. Obwohl die Anwendbarkeit der Modelle auf die hier untersuchten Fälle beschränkt ist, können sie sich als hilfreiche Werkzeuge bei der Entwicklung von Kugelarrays für Auralisationsanwendungen erweisen.
https://nbn-resolving.org/urn:nbn:de:gbv:ilm1-2019000222
How tone mapping influences the bit rate and the bit depth of coded sequences. - In: SMPTE motion imaging journal, ISSN 2160-2492, Bd. 127 (2018), 5, S. 38-43
In recent years, high dynamic range (HDR) made major steps forward to become the next big broadcast technology. It is generally accepted that HDR will need a higher bit rate because of more quantization steps and the fact that the images deal with much more detail in the highlights and shadows. However, it is only insufficiently taken into account that most of these details will be preserved when performing an HDR downconversion using tone mapping. It remains unclear how the standard dynamic range bit rate is influenced by the HDR production. Therefore, peak signal-to-noise ratio measurements have been performed, and detailed explanations of the reasons are given in this paper. Moreover, it is not definitively known if the strong manipulation on the luminance component at downconversion can produce artifacts like banding. To provide information, the incoming bit depth of the HDR with subsequent tone mapping is verified by a viewing test.
https://doi.org/10.5594/JMI.2018.2810021
Innovative methods and technologies for spatial listening and speech intelligibility using hearing implants. - In: Adaptive processes in hearing, (2018), S. 343-350