<p>Bilaga: 1 CD</p>

This thesis describes a system that can be used for the decoding of a three dimensional audio recording over headphones or two, or more, speakers. A literature review of psychoacoustics and a review (both historical and current) of surround sound systems is carried out. The need for a system which is platform independent is discussed, and the proposal for a system based on an amalgamation of Ambisonics, binaural and transaural reproduction schemes is given. In order for this system to function optimally, each of the three systems rely on providing the listener with the relevant psychoacoustic cues. The conversion from a five speaker ITU array to binaural decode is well documented but pair-wise panning algorithms will not produce the correct lateralisation parameters at the ears of a centrally seated listener. Although Ambisonics has been well researched, no one has, as yet, produced a psychoacoustically optimised decoder for the standard irregular five speaker array as specified by the ITU as the original theory, as proposed by Gerzon and Barton (1992) was produced (known as a Vienna decoder), and example solutions given, before the standard had been decided on. In this work, the original work by Gerzon and Barton (1992) is analysed, and shown to be suboptimal, showing a high/low frequency decoder mismatch due to the method of solving the set of non-linear simultaneous equations. A method, based on the Tabu search algorithm, is applied to the Vienna decoder problem and is shown to provide superior results to those shown by Gerzon and Barton (1992) and is capable of producing multiple solutions to the Vienna decoder problem. During the write up of this report Craven (2003) has shown how 4th order circular harmonics (as used in Ambisonics) can be used to create a frequency independent panning law for the five speaker ITU array, and this report also shows how the Tabu search algorithm can be used to optimise these decoders further. A new method is then demonstrated using the Tabu search algorithm coupled with lateralisation parameters extracted from a binaural simulation of the Ambisonic system to be optimised (as these are the parameters that the Vienna system is approximating). This method can then be altered to take into account head rotations directly which have been shown as an important psychoacoustic parameter in the localisation of a sound source (Spikofski et al., 2001) and is also shown to be useful in differentiating between decoders optimised using the Tabu search form of the Vienna optimisations as no objective measure had been suggested. Optimisations for both Binaural and Transaural reproductions are then discussed so as to maximise the performance of generic HRTF data (i.e. not individualised) using inverse filtering methods, and a technique is shown that minimises the amount of frequency dependant regularisation needed when calculating cross-talk cancellation filters.

With the development of technology over the past decade and the former challenges of virtual environments mitigated, the need for further study of human interaction with these environments has grown apparent. The visual and interaction components for virtual reality applications have been comprehensively studied, but a lack of spatial audio fidelity leaves a need for understanding how well humans can localize aural cues and discern audio-visual disparity in these virtual environments. In order for development of accurate and efficient levels of audio fidelity, a human study was conducted with 18 participants to see how far a bimodal audio and visual cue need to separate for someone to notice. As suspected, having a visual component paired with an auditory one led to biasing toward the visual component. The average participant noticed a disparity when the audio component was 33.7° apart from the visual one, pertaining to the azimuth. There was no significant evidence to suggest that speed or direction of audio component disparity led to better localization performance by participant. Presence and prior experience did not have an effect on localization performance; however, a larger participant base may be needed to draw further conclusions. Increase in localization ability was observed within a few practice rounds for participants. Overall, performance in virtual reality was parallel to augmented reality performance when a visual source biased sound localization, and can this be a both tool and design constraint for virtual environment developers. / Master of Science / Virtual Reality has overcame a large technological gap over the past decade, allowing itself to be a strong tool in many applications from training to entertainment. The need for studying audio fidelity in virtual environments has emerged from a gap of research in the virtual reality domain. Therefore, a human participant study was conducted to see how well they could localize sound in a virtual environment. This involved signaling when they noticed a visual object and a sound split. The average of 72 trials with 18 participants was 33.7° of separation on the horizontal plane. This can be both a tool and a design constraint for virtual reality developers, who can use this visual biasing as a guideline for future applications.

Musik och rörelser har sedan urminnes tider varit nära bundna via dansen, men detta sambandet har för det mesta varit endimensionellt i den mening att en eller fler människor som reagerar till musik eller ljud av något slag. Här har vi sett att det finns ett intressant rumsligt, interaktivt och sinnligt utforskande att göra. Via ambisonics, en teknik för att panorera ljud i tre dimensioner och en Kinect kamera har vi utforskat vad som sker när en vänder på detta sambandet och låter ljudet reagera till människans rörelse istället. Men här finns mer att utforska än bara sambandet mellan musik och dans. En av de för oss mest intressanta delarna har varit hur det går att utveckla en ljudinstallation där ljuden som spelas upp motsvarar rörelserna som skapar dem. Med sensory ethnography som perspektiv har vi under ett antal workshops tillsammans med personer med en bakgrund inom dans och uppträde undersökt vilken roll kinestesi och agens har i detta möte mellan rörelse och ljud. Vad vi funnit utifrån diffrakterande analys är hur agens, förkunskap och precision spelar stor roll för upplevelsen av kontroll i en installation som våran; men även hur rumsligt utforskande och lekfullhet kan träda fram när ovannämnda kriterier uteblir. / Music and motion have shared an intimate connection through dance since ages past, however this bond has for the most part been one dimensional in the sense that people are the ones reacting to music. This connection is something we have found intriguing to explore through the aspects of interactivity, spaciousness and sensory experience. Using ambisonics, a technology used to recreate three dimensional sound fields and a Kinect camera, we have sought out to investigate what happens if you reverse this connection and let audio react to a person's movement instead. There is however more to this than just the bond between dance and music. One of the more interesting aspects has been how an audio installation can be developed to play back audio that corresponds to the movements that generate them. We have through the usage of sensory ethnography as our exploratory perspective enacted a number of workshops where we, together with people with a background in dance and performance, investigated the role that kinaesthesia and a person's sense of agency has in this interconnection of motion and sound. What we have found is how agency, precognition and precision plays a vital role in how well the sense of control is experienced in an installation such as ours; but also how a more spacious and playful exploration can emerge when the above mentioned criterias are absent.

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Dans ce travail nous étudions la problématique des ingénieurs du son face au mixage d’un microphone principal HOA avec des microphones d’appoint, et notamment l’estimation des paramètres tels que le retard, la position et le gain des sources acoustiques associées aux microphones d’appoint. Nous proposons un algorithme fournissant les paramètres estimés (retard, position, gain) basé sur des équations d’encodage spatial au format HOA qui peuvent alors être utilisées pour traiter les signaux des microphones d’appoint durant le mixage. Cette extraction automatique des paramètres peut être vue comme une assistance pour les ingénieurs du son, leur permettant d’éviter un travail à faible valeur ajoutée (mesure de la distance et des angles entre microphones) afin de pouvoir se concentrer sur des problèmes artistiques comme l’ajustement des paramètres de niveau, d’égalisation ou de compression, voire l’ajustement fin des paramètres de retard, position, gain. La robustesse de l’algorithme est bien présentée pour les scènes sonores de différents niveaux de complexité (plusieurs sources acoustiques, réverbération, encodage réel du microphone…). Nous proposons des tests de performances pour les scènes sonores simulées et réels afin de montrer l’efficacité de l’algorithme ainsi que ces limites. La conclusion et les perspectives pour des futurs travaux complètent cette thèse à la fin du document. / In this thesis we study the problematic of a sound engineer mixing HOA (Higher Order Ambisonics) and spot microphones, namely the estimation of parameters such as delay, position and gain of acoustic sources associated to spot microphones. We present a typical workflow in this context, and also propose an algorithm extracting parameters that could be applied to the spot microphone signals. This mixing assistance allows sound engineers to easily work with HOA 3D sound and to concentrate on artistic choices (fine adjustments of the parameters), by avoiding a low-added value work (coarse parameter estimation). The robustness of the estimators is evaluated on recorded and artificial sound scenes, with different degrees of complexity in terms of number of sources and acoustic conditions (reverberation, effect of real microphone encoding, …). We also provide performance evaluations, based on both sound scene simulations and real recordings, showing encouraging results along with actual limits, and conclude on perspectives.

L'objectif de cette thèse est l'optimisation de la qualité perçue de la reproduction sonore par un système audio multicanal, dans un contexte de salle d'écoute domestique. Les travaux de recherche présentés s'articulent selon deux axes. Le premier concerne l'effet de salle, et plus particulièrement les aspects physiques et perceptifs liés aux premières réflexions d'une salle. Ces éléments sont décrits spécifiquement, et une expérience psychoacoustique a été menée afin d'étendre les données disponibles quant à leur perceptibilité, c'est à dire leur capacité à modifier la perception du son direct, que ce soit en termes de timbre ou de localisation. Les résultats mettent en évidence la dépendance du seuil en fonction du type de stimulus, ainsi que son évolution en fonction de la configuration spatiale de l'onde directe et de la réflexion. Pour une condition donnée, le seuil de perceptibilité est décrit comme une fonction de directivité dépendant de l'incidence de la réflexion.Le deuxième axe de travail concerne les méthodes de correction de l'effet de la salle de reproduction. Les méthodes numériques classiques sont d'abord étudiées. Leur principale lacune réside dans l'absence de prise en compte du rôle spécifique des propriétés temporelles et spatiales des première réflexions. Le travail de thèse se termine par la proposition d'une nouvelle méthode de correction utilisant un algorithme itératif de type FISTA modifié afin de prendre en compte la perceptibilité des réflexions. Le traitement est implémenté dans une représentation où l'information spatiale est analysée sur la base des harmoniques sphériques. / The goal of this Ph. D. thesis is to optimize the perceived quality of multichannel sound reproduction systems, in the context of a domestic listening room. The presented research work have been pursued in two different directions.The first deals with room effet, and more particularly with physical and perceptual aspects of first reflections within a room. These reflections are specifically described, and a psychoacoustical experiment have been carried out in order to extend the available data on their perceptibility, i.e. their potency in altering the perception of the direct sound, whether in its timbral or spatial features. Results exhibit the variation of the threshold depending on the type of stimulus, as well as on the spatial configuration of the direct sound and the reflection. For a given condition, the perceptibility threshold is given as a directivity function depending on the direction of incidence of the reflection.The second topic deals with room correction methods. Firstly, state-of-the art digital methods are investigated. Their main drawback is that they don't consider the specific impact of the temporal and spatial attributes of first reflections. A new correction method is therefore proposed. It uses an iterative algorithm, derivated from the FISTA method, in order to take into account the perceptibility of the reflections. All the processing is carried out in a spatial sound representation, where the spatial properties of the sound are analysed thanks to spherical harmonics.

Detta examensarbete innefattar en utforskning om mitt arbete med immersivt ljud och hur det har påverkat min konstnärliga praktik som musikproducent. Utforskningen görs genom en analys av tre delstudier bestående av en 360-video som spelades in i S:t Jakobskyrkan i Stockholm, en VR upplevelse i en virtuell kopia av Nathan Milsteinsalen på Kungliga Musikhögskolan, samt en komposition som producerades med Dolby Atmos. Slutsatsen som dras är att arbetet har påverkat min konstnärliga praktik genom att ge mig nya insikter på komponerande, inspelning, och mixning. Slutligen ges förslag på fortsatta studier om audiovisuella metoder för immersiv musikproduktion samt nya infallsvinklar på stereomixning som är informerade av immersivt ljud. / This thesis examines how working with immersive audio has affected my artistic practice as a music producer. It does so by examining the insights gained during the production of three case studies consisting of a 360-video recorded at Saint James’s Church in Stockholm, Sweden, a Virtual Reality (VR) experience in a 3D replica of Nathan Milstein Hall at the Royal College of Music in Stockholm, as well as a composition produced using Dolby Atmos. The paper concludes that working with the case studies has changed my artistic practice by leading to new insights in the areas of composing, recording, and mixing. The paper also suggests future studies into the use of audiovisual approaches to immersive music production as well as considerations for stereo mix techniques based on insights gained from immersive audio.

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This research dissertation presents work undertaken to develop new performance techniques and mappings for the expressive control of spatial motion using Ambisonic projection. The dissertation reviews relevant research from the fields of Spatial Sound and Extended Instruments, and establishes playability as a useful set of criteria for a reflexive project methodology and evaluation. This reflexive research systematically investigates Trevor Wishart’s taxonomy of spatial motions through the development of new hardware, software, performance techniques and spatial motion analysis.