A methodology for sound scene manipulation based on the ray space transform

In this paper we devise a methodology for analysing and subsequently manipulating a sound scene acquired by means of a uniform linear array of microphones. The array signal is transformed in the ray space, i.e. a domain where acoustic rays are points; here we extract the source position and orientation in space and its radiation pattern, while its signal is extracted by a near-field beamformer. These descriptors can be easily manipulated and provided to any parametric rendering system. Through simulations we have proven the capability of the proposed method to perform different manipulations

Efficient Continuous Beam Steering for Planar Arrays of Differential Microphones

Performing continuous beam steering, from planar arrays of high-order differential microphones, is not trivial. The main problem is that shape-preserving beams can be steered only in a finite set of privileged directions, which depend on the position and the number of physical microphones. In this letter, we propose a simple and computationally inexpensive method for alleviating this problem using planar microphone arrays. Given two identical reference beams pointing in two different directions, we show how to build a beam of nearly constant shape, which can be continuously steered between such two directions. The proposed method, unlike the diffused steering approaches based on linear combinations of eigenbeams (spherical harmonics), is applicable to planar arrays also if we deal with beams characterized by high-order polar patterns. Using the coefficients of the Fourier series of the polar patterns, we also show how to find a tradeoff between shape invariance of the steered beam, and maximum angular displacement between the two reference beams. We show the effectiveness of the proposed method through the analysis of models based on first-, second-, and third-order differential microphones

Investigating Networked Music Performances in Pedagogical Scenarios for the InterMUSIC Project

With the big improvement of digital communication networks, Networked Music Performances (NMP) received a great interest from music live performance and music recording industry. The positive impact of NMP in pedagogical appli- cations, instead, has been only preliminary explored. Within the InterMUSIC project, we aim to investigate NMP from a pedagogical perspective, that has considerable differences with respect to music performances, and to develop tools to improve distance learning experiences. In this paper, we introduce a conceptual framework designed to be the foundation for all the experiments conducted in the project. We also present two preliminary experiments that investigate the sense of presence of geographically-distant musicians in a distance learning scenario. We discuss the comments provided by the musicians as a set of requirements and guidelines for future experiments

Aspects of room acoustics, vision and motion in the human auditory perception of space

The human sense of hearing contributes to the awareness of where sound-generating objects are located in space and of the environment in which the hearing individual is located. This auditory perception of space interacts in complex ways with our other senses, can be both disrupted and enhanced by sound reflections, and includes safety mechanisms which have evolved to protect our lives, but can also mislead us. This dissertation explores some selected topics from this wide subject area, mostly by testing the abilities and subjective judgments of human listeners in virtual environments. Reverberation is the gradually decaying persistence of sounds in an enclosed space which results from repeated sound reflections at surfaces. The first experiment (Chapter 2) compared how strongly people perceived reverberation in different visual situations: when they could see the room and the source which generated the sound; when they could see some room and some sound source, but the image did not match what they heard; and when they could not see anything at all. There were no indications that the visual image had any influence on this aspect of room-acoustical perception. The potential benefits of motion for judging the distance of sound sources were the focus of the second study (Chapter 3), which consists of two parts. In the first part, loudspeakers were placed at different depths in front of sitting listeners who, on command, had to either remain still or move their upper bodies sideways. This experiment demonstrated that humans can exploit motion parallax (the effect that closer objects appear faster to a moving observer than farther objects) with their ears and not just with their eyes. The second part combined a virtualisation of such sound sources with a motion platform to show that the listeners’ interpretation of this auditory motion parallax was better when they performed this lateral movement by themselves, rather than when they were moved by the apparatus or were not actually in motion at all. Two more experiments were concerned with the perception of sounds which are perceived as becoming louder over time. These have been called “looming”, as the source of such a sound might be on a collision course. One of the studies (Chapter 4) showed that western diamondback rattlesnakes (Crotalus atrox) increase the vibration speed of their rattle in response to the approach of a threatening object. It also demonstrated that human listeners perceive (virtual) snakes which engage in this behaviour as especially close, causing them to keep a greater margin of safety than they would otherwise. The other study (section 5.6) was concerned with the well-known looming bias of the sound localisation system, a phenomenon which leads to a sometimes exaggerated, sometimes more accurate perception of approaching compared to receding sounds. It attempted to find out whether this bias is affected by whether listeners hear such sounds in a virtual enclosed space or in an environment with no sound reflections. While the results were inconclusive, this experiment is noteworthy as a proof of concept: It was the first study to make use of a new real-time room-acoustical simulation system, liveRAZR, which was developed as part of this dissertation (Chapter 5). Finally, while humans have been more often studied for their unique abilities to communicate with each other and bats for their extraordinary capacity to locate objects by sound, this dissertation turns this setting of priorities on its head with the last paper (Chapter 6): Based on recordings of six pale spear-nosed bats (Phyllostomus discolor), it is a survey of the identifiably distinct vocalisations observed in their social interactions, along with a description of the different situations in which they typically occur.Das menschliche Gehör trägt zum Bewusstsein dafür bei, wo sich schallerzeugende Objekte im Raum befinden und wie die Umgebung beschaffen ist, in der sich eine Person aufhält. Diese auditorische Raumwahrnehmung interagiert auf komplexe Art und Weise mit unseren anderen Sinnen, kann von Schallreflektionen sowohl profitieren als auch durch sie behindert werden, und besitzt Mechanismen welche evolutionär entstanden sind, um unser Leben zu schützen, uns aber auch irreführen können. Diese Dissertation befasst sich mit einigen ausgewählten Themen aus diesem weiten Feld und stützt sich dabei meist auf die Testung von Wahrnehmungsfähigkeiten und subjektiver Einschätzungen menschlicher Hörer/-innen in virtueller Realität. Beim ersten Experiment (Kapitel 2) handelte es sich um einen Vergleich zwischen der Wahrnehmung von Nachhall, dem durch wiederholte Reflexionen an Oberflächen hervorgerufenen, sukzessiv abschwellenden Verbleib von Schall in einem umschlossenen Raum, unter verschiedenen visuellen Umständen: wenn die Versuchsperson den Raum und die Schallquelle sehen konnte; wenn sie irgendeinen Raum und irgendeine Schallquelle sehen konnte, dieses Bild aber vom Schalleindruck abwich; und wenn sie gar kein Bild sehen konnte. Dieser Versuch konnte keinen Einfluss eines Seheindrucks auf diesen Aspekt der raumakustischen Wahrnehmung zu Tage fördern. Mögliche Vorteile von Bewegung für die Einschätzung der Entfernung von Schallquellen waren der Schwerpunkt der zweiten Studie (Kapitel 3). Diese bestand aus zwei Teilen, wovon der erste zeigte, dass Hörer/-innen, die ihren Oberkörper relativ zu zwei in unterschiedlichen Abständen vor ihnen aufgestellten Lautsprechern auf Kommando entweder stillhalten oder seitlich bewegen mussten, im letzteren Falle von der Bewegungsparallaxe (dem Effekt, dass sich der nähere Lautsprecher relativ zum sich bewegenden Körper schneller bewegte als der weiter entfernte) profitieren konnten. Der zweite Teil kombinierte eine Simulation solcher Schallquellen mit einer Bewegungsplattform, wodurch gezeigt werden konnte, dass die bewusste Eigenbewegung für die Versuchspersonen hilfreicher war, als durch die Plattform bewegt zu werden oder gar nicht wirklich in Bewegung zu sein. Zwei weitere Versuche gingen auf die Wahrnehmung von Schallen ein, deren Ursprungsort sich nach und nach näher an den/die Hörer/-in heranbewegte. Derartige Schalle werden auch als „looming“ („anbahnend“) bezeichnet, da eine solche Annäherung bei bedrohlichen Signalen nichts Gutes ahnen lässt. Einer dieser Versuche (Kapitel 4) zeigte zunächst, dass Texas-Klapperschlangen (Crotalus atrox) die Vibrationsgeschwindigkeit der Schwanzrassel steigern, wenn sich ein bedrohliches Objekt ihnen nähert. Menschliche Hörer/-innen nahmen (virtuelle) Schlangen, die dieses Verhalten aufweisen, als besonders nahe wahr und hielten einen größeren Sicherheitsabstand ein, als sie es sonst tun würden. Der andere Versuch (Abschnitt 5.6) versuchte festzustellen, ob die wohlbekannte Neigung unserer Schallwahrnehmung, näherkommende Schalle manchmal übertrieben und manchmal genauer einzuschätzen als sich entfernende, durch Schallreflektionen beeinflusst werden kann. Diese Ergebnisse waren unschlüssig, jedoch bestand die Besonderheit dieses Versuchs darin, dass er erstmals ein neues Echtzeitsystem zur Raumakustiksimulation (liveRAZR) nutzte, welches als Teil dieser Dissertation entwickelt wurde (Kapitel 5). Abschließend (Kapitel 6) wird die Schwerpunktsetzung auf den Kopf gestellt, nach der Menschen öfter auf ihre einmaligen Fähigkeiten zur Kommunikation miteinander untersucht werden und Fledermäuse öfter auf ihre außergewöhnliches Geschick, Objekte durch Schall zu orten: Anhand von Aufnahmen von sechs Kleinen Lanzennasen (Phyllostomus discolor) fasst das Kapitel die klar voneinander unterscheidbaren Laute zusammen, die diese Tiere im sozialen Umgang miteinander produzieren, und beschreibt, in welchen Situationen diese Lauttypen typischerweise auftreten

Inferring Room Geometries

Determining the geometry of an acoustic enclosure using microphone arrays has become an active area of research. Knowledge gained about the acoustic environment, such as the location of reflectors, can be advantageous for applications such as sound source localization, dereverberation and adaptive echo cancellation by assisting in tracking environment changes and helping the initialization of such algorithms. A methodology to blindly infer the geometry of an acoustic enclosure by estimating the location of reflective surfaces based on acoustic measurements using an arbitrary array geometry is developed and analyzed. The starting point of this work considers a geometric constraint, valid both in two and three-dimensions, that converts time-of-arrival and time-difference-pf-arrival information into elliptical constraints about the location of reflectors. Multiple constraints are combined to yield the line or plane parameters of the reflectors by minimizing a specific cost function in the least-squares sense. An iterative constrained least-squares estimator, along with a closed-form estimator, that performs optimally in a noise-free scenario, solve the associated common tangent estimation problem that arises from the geometric constraint. Additionally, a Hough transform based data fusion and estimation technique, that considers acquisitions from multiple source positions, refines the reflector localization even in adverse conditions. An extension to the geometric inference framework, that includes the estimation of the actual speed of sound to improve the accuracy under temperature variations, is presented that also reduces the required prior information needed such that only relative microphone positions in the array are required for the localization of acoustic reflectors. Simulated and real-world experiments demonstrate the feasibility of the proposed method.Open Acces

Sonic Interactions in Virtual Environments

This open access book tackles the design of 3D spatial interactions in an audio-centered and audio-first perspective, providing the fundamental notions related to the creation and evaluation of immersive sonic experiences. The key elements that enhance the sensation of place in a virtual environment (VE) are: Immersive audio: the computational aspects of the acoustical-space properties of Virutal Reality (VR) technologies Sonic interaction: the human-computer interplay through auditory feedback in VE VR systems: naturally support multimodal integration, impacting different application domains Sonic Interactions in Virtual Environments will feature state-of-the-art research on real-time auralization, sonic interaction design in VR, quality of the experience in multimodal scenarios, and applications. Contributors and editors include interdisciplinary experts from the fields of computer science, engineering, acoustics, psychology, design, humanities, and beyond. Their mission is to shape an emerging new field of study at the intersection of sonic interaction design and immersive media, embracing an archipelago of existing research spread in different audio communities and to increase among the VR communities, researchers, and practitioners, the awareness of the importance of sonic elements when designing immersive environments

Sonic interactions in virtual environments

This book tackles the design of 3D spatial interactions in an audio-centered and audio-first perspective, providing the fundamental notions related to the creation and evaluation of immersive sonic experiences. The key elements that enhance the sensation of place in a virtual environment (VE) are: Immersive audio: the computational aspects of the acoustical-space properties of Virutal Reality (VR) technologies Sonic interaction: the human-computer interplay through auditory feedback in VE VR systems: naturally support multimodal integration, impacting different application domains Sonic Interactions in Virtual Environments will feature state-of-the-art research on real-time auralization, sonic interaction design in VR, quality of the experience in multimodal scenarios, and applications. Contributors and editors include interdisciplinary experts from the fields of computer science, engineering, acoustics, psychology, design, humanities, and beyond. Their mission is to shape an emerging new field of study at the intersection of sonic interaction design and immersive media, embracing an archipelago of existing research spread in different audio communities and to increase among the VR communities, researchers, and practitioners, the awareness of the importance of sonic elements when designing immersive environments

Listening to Distances and Hearing Shapes:Inverse Problems in Room Acoustics and Beyond

A central theme of this thesis is using echoes to achieve useful, interesting, and sometimes surprising results. One should have no doubts about the echoes' constructive potential; it is, after all, demonstrated masterfully by Nature. Just think about the bat's intriguing ability to navigate in unknown spaces and hunt for insects by listening to echoes of its calls, or about similar (albeit less well-known) abilities of toothed whales, some birds, shrews, and ultimately people. We show that, perhaps contrary to conventional wisdom, multipath propagation resulting from echoes is our friend. When we think about it the right way, it reveals essential geometric information about the sources--channel--receivers system. The key idea is to think of echoes as being more than just delayed and attenuated peaks in 1D impulse responses; they are actually additional sources with their corresponding 3D locations. This transformation allows us to forget about the abstract \emph{room}, and to replace it by more familiar \emph{point sets}. We can then engage the powerful machinery of Euclidean distance geometry. A problem that always arises is that we do not know \emph{a priori} the matching between the peaks and the points in space, and solving the inverse problem is achieved by \emph{echo sorting}---a tool we developed for learning correct labelings of echoes. This has applications beyond acoustics, whenever one deals with waves and reflections, or more generally, time-of-flight measurements. Equipped with this perspective, we first address the ``Can one hear the shape of a room?'' question, and we answer it with a qualified ``yes''. Even a single impulse response uniquely describes a convex polyhedral room, whereas a more practical algorithm to reconstruct the room's geometry uses only first-order echoes and a few microphones. Next, we show how different problems of localization benefit from echoes. The first one is multiple indoor sound source localization. Assuming the room is known, we show that discretizing the Helmholtz equation yields a system of sparse reconstruction problems linked by the common sparsity pattern. By exploiting the full bandwidth of the sources, we show that it is possible to localize multiple unknown sound sources using only a single microphone. We then look at indoor localization with known pulses from the geometric echo perspective introduced previously. Echo sorting enables localization in non-convex rooms without a line-of-sight path, and localization with a single omni-directional sensor, which is impossible without echoes. A closely related problem is microphone position calibration; we show that echoes can help even without assuming that the room is known. Using echoes, we can localize arbitrary numbers of microphones at unknown locations in an unknown room using only one source at an unknown location---for example a finger snap---and get the room's geometry as a byproduct. Our study of source localization outgrew the initial form factor when we looked at source localization with spherical microphone arrays. Spherical signals appear well beyond spherical microphone arrays; for example, any signal defined on Earth's surface lives on a sphere. This resulted in the first slight departure from the main theme: We develop the theory and algorithms for sampling sparse signals on the sphere using finite rate-of-innovation principles and apply it to various signal processing problems on the sphere

Sonic Interactions in Virtual Environments

This open access book tackles the design of 3D spatial interactions in an audio-centered and audio-first perspective, providing the fundamental notions related to the creation and evaluation of immersive sonic experiences. The key elements that enhance the sensation of place in a virtual environment (VE) are: Immersive audio: the computational aspects of the acoustical-space properties of Virutal Reality (VR) technologies Sonic interaction: the human-computer interplay through auditory feedback in VE VR systems: naturally support multimodal integration, impacting different application domains Sonic Interactions in Virtual Environments will feature state-of-the-art research on real-time auralization, sonic interaction design in VR, quality of the experience in multimodal scenarios, and applications. Contributors and editors include interdisciplinary experts from the fields of computer science, engineering, acoustics, psychology, design, humanities, and beyond. Their mission is to shape an emerging new field of study at the intersection of sonic interaction design and immersive media, embracing an archipelago of existing research spread in different audio communities and to increase among the VR communities, researchers, and practitioners, the awareness of the importance of sonic elements when designing immersive environments