Thesis

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The influence of reverberation on externalization

Authors Giller, P.
Year 2019
Thesis Type Master's thesis
Topic Psychoacoustics
Abstract Realistic binaural synthesis produces well externalized sound images. Externalization is a subjective quantity that refers to the sensation of auditory events being located outside the listener's head. It is a fragile experience which, in addition to the sound field at the entrance of the ear canals, also depends on visual cues, training, and expectation. Various studies have examined perceptual and technical aspects of the phenomenon. It was found that the presence of reverberation can increase the degree of externalization. Furthermore, recent findings indicate the benefit of individual HRTFs may be negligible in reverberant conditions. This work investigates how reverberation influences externalization in a listening experiment, considering different HRTFs and listening conditions. Techniques shall be developed to add helpful reverberation cues to generic HRTFs while preserving the original room impression and sound coloration. Ideally, the results will be integrated in an application for robust binaural rendering of virtual sound scenes.
Supervisors Wendt, F., Höldrich, R.
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Acoustic Analysis of the modern Recorder

Authors Kocher, L.
Year 2019
Thesis Type Bachelor's thesis
Topic Audio Signal Processing
Keywords Klanganalyse
Abstract This thesis considers the acoustic analysis of the so-called Helder Tenor, a modern recorder. Since the Helder Tenor is a rather new instrument and poorly studied, the analysis is focused on the frequency response characteristics and the partial harmonics of the flute. In order to make any conclusions, a baroque model, the most common used recorder model, and two more, are analysed, too. This allows to draw a direct comparison from the new model, which is still in development, to a well-tried model. Ultimately, the thesis should provide an interpretation of the main differences and advantages of the Helder Tenor compared to other, older recorder models.
URL http://phaidra.kug.ac.at/o:79028
Supervisors Höldrich, R.
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Sound generator for rolling- and wind noise

Authors Koch, J.
Year 2019
Thesis Type Master's thesis
Topic Audio Signal Processing
Keywords Sound Design
Abstract Nowadays driving simulators are an important testing tool in the automotive industry. The most important feature is naturally the realistic simulation of the driving feeling. Besides the mechanical/optical simulation, also the realistic soundfield in the driver's cab (which generally consists of engine-, rolling- and wind noises) play an important role. While the mechanical/optical simulation is often a subject of great interest, the realistic soundfield in the driver's cab is rather neglected most of the time. In the course of this master thesis, a sound module for rolling- and wind noise will be developed for Magna Steyr, which will be integrated into an already existing Matlab/Simulink model. By analysing different data sets , a connection between characteristic rolling-/wind noises and driving parameters (such as speed, condition of the road, gear position...) should be established, to subsequently re-synthesize those characteristic noises in Matlab/Simulink by only using these parameters. In addition, a model evaluation/validation through specially adapted listening tests is planned in order to assess the quality of the model and to clarify the question "How important is the rolling/wind noise for a realistic speed impression?"
Supervisors Sontacchi, A.
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Interactive virtual walkthrough by position-dependent interpolation of first-order room impulse responses

Authors Müller, K.
Year 2019
Thesis Type Master's thesis
Topic Spatial Audio
Abstract The spatial decomposition method (SDM) enables the mapping of first-order ambisonic room impulse responses to arbitrary higher orders. Thus, a sharper directionality of sound sources and reverberation can be achieved. Based on the SDM an efficient method for position-dependent interpolation of ambisonic room impulse responses will be developed first. Then influences of single components of the utilized approach will be evaluated to achieve a computational efficient algorithm which only deals with the necessary components. Finally, utilizing the position-dependent interpolation of a finite number of measured room impulse responses, a virtual acoustic walk through the room will be possible. To preserve natural acoustics when moving in the virtual room, the real-time capable algorithm is focused on consistent source positions, timbre and room impression related to the reference measurements.
Supervisors Zotter, F., Höldrich, R.
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Distance-coded Ambisonics Formats and their Reproduction on Headphones and Loudspeaker Arrays

Authors Riedel, S.
Year 2019
Thesis Type Audio Engineering project
Topic Spatial Audio
Abstract This work introduces distance-coded Ambisonics formats and their reproduction on headphones and loudspeaker arrays. The first simple and practically motivated format proposes two ambisonic streams, a far-field and a near-field stream, to which sounds are distributed according to a distance parameter at encoding stage. In binaural decoding this enables the application of near-field HRTFs with inherent binaural cues which cannot be applied at encoding stage, for example the frequency-dependent increase in interaural level differences compared to far-field HRIRs. Blending between two ambisonic reverberation patterns (model or measured DRIR) is combined with a physically meaningful level attenuation to achieve a plausible distance effect that includes a change in the direct-to-reverberant sound energy ratio. Compatibility with loudspeaker arrays is given by combining the two ambisonic streams into one single stream after introducing differences in level and the two reverberation patterns to retain a relative distance effect. An efficient and more accurate way to render distance is to restrict the effect to the horizontal plane. Therefore, a second format that interprets negative elevation as the distance of a horizontal source is proposed. In binaural reproduction, this format allows for a high spatial resolution in the precomputation of distance-dependent HRTFs and early reflections, applied at decoding stage. Moreover, this format could motivate future research on loudspeaker systems that employ horizontal sound field synthesis (rendering of near-field sources) combined with AllRAD for elevated sources.
Supervisors Höldrich, R.
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Discrimination of short frequency glides depending on reverberation

Authors Brands, B.
Year 2019
Thesis Type Bachelor's thesis
Topic Psychoacoustics
Abstract Differences in phase or group-delay are crucial properties that help the ear to discriminate between short sounds. To obtain further insights in the ability of short-time discrimination of the auditory system, a forced-choice adaptive listening experiment was performed. The subjects were exposed to chirp-like sounds varying in length, direction of the chirp and added reverberation. These chirp-like sounds were rendered by filtering test-signals with an all-pass filter with logarithmic group-delay. The group-delay was varied and the just notable difference (JND) between the logarithmic group-delay of two stimuli was measured. The results depict that by adding more reverberation, the discrimination decreased. Furthermore, upward chirp-like sounds were discriminable in a better way than downward chirp-like sounds and so were short versus long stimulus lengths. The influence of direction was only significant for short durations.
Supervisors Höldrich, R.
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Tangible user interface for sound field control

Authors Roenisch, T., Haider, M.
Year 2019
Thesis Type Bachelor's thesis
Topic Interaction Design
Keywords Auditory Visual Environment
Abstract Controlling the origin of sound sources in a three-dimensional audio field is a complex task, particularly in a live environment. Since multiple sources can be involved, a good overview, fast access to every source and simple automation commands are required. A user interface should facilitate straightforward handling and situational awareness. The following thesis presents the further development of "A Tangible User Interface for Playing Virtual Acoustics" by Birgit Gasteiger in 2010, with an emphasis on improved usability and advanced Ambisonic-controls and automation. Furthermore, it strives to devine a field of application for the "Tangible User Interface for Auditory Virtual Environments" (TUI-AVE). Several controls for the spatialization of sound sources, the respective development as well as designs of the corresponding visual presentation are outlined.
Supervisors Ritsch, W.
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Room divergence effect in virtual environments

Authors Enge, K.
Year 2019
Thesis Type Master's thesis
Topic Audio Signal Processing
Abstract Virtual reality environments are becoming an increasingly important factor in various applications such as architecture, film and computer games. For a long time, all these areas concentrated primarily on visual impressions. It is undisputed, however, that three-dimensional sound plays an important role in the credibility of virtual environments, if only for the reason that humans characterize real space to a large extent by listening. For the ears, the equivalent of VR glasses is binaural reproduction via headphones. The virtualization of real spaces using CAD-programs opens up new possibilities for psychoacoustic investigations, namely with binaural sounds in virtual spaces. How do virtualization and binaural reproduction influence each other? Does virtualization have an effect on the perceived externalization, distance and direction of binaural reproduction? Can the room divergence effect also be shown in virtual environments? How detailed must spaces be modelled in order to achieve credible experiences for test subjects? Does the possibility of physical movement around a source change the results? Is it possible to "learn" the virtual environment by walking through it? In order to investigate such questions, several spaces with different virtualization techniques will be used: One space by modeling in Unity, one by photo projection on a rectangular virtual space and one by photogrammetry. In these spaces, appropriate psychoacoustic investigations are carried out.
Supervisors Frank, M., Höldrich, R.
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Classification of mechanical noises of motorised cylinder locks

Authors Merz, P.
Year 2019
Thesis Type Audio Engineering project
Topic Audio Signal Processing
Keywords psychoacoustics, Music Information Retrieval
Abstract This thesis examines the classifiability of mechanical noises. The used test data is a set of recordings of motorised cylinder locks, which have been classified according to their build quality. Methods from unsupervised machine learning will be used to study whether it is possible or not to reproduce the classification based on a selection of psychoacoustic features implemented in Python. Finally it will be examined if this classification can also be done automatically.
Supervisors Sontacchi, A.
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Derivative-based regularization of inverse problems in acoustic holography

Authors Pagavino, M.
Year 2019
Thesis Type Master's thesis
Topic Audio Signal Processing
Keywords acoustic holography
Abstract The visualization of the sound field close to the source is often helpful to understand the vibroacoustic origin. This gave rise to the development of several acoustic imaging techniques that can be used to model the measured sound field radiated by an arbitrary source. One of these models is the equivalent source method (ESM). It models the local sound field by superimposing distributed elementary sources of different strengths. From spatially discrete sound pressure measurements, the strength of these sources can be determined through solving a linear inverse problem. Due to the underdetermined and ill-posed nature of the inverse problem, the introduction of some form of regularization is a prerequisite for obtaining a meaningful solution. Imposing additional constraints on the solution to enforce expected spatial structures can provide suitable regularization. Inverse problems with constraints typically minimize some norm functional acting on the spatial domain. Sparsity promotion through Compressive Sensing, based on L1-norm minimization, has received increasing attention in recent years due to its ability of providing solutions that are valid beyond the spatial sampling limit. However, typical vibroacoustic source phenomena are not necessarily spatially sparse themselves, as they frequently contain spatially distributed patterns as well. This thesis regards regularization methods that impose sparsity on first- and second-order spatial derivatives. This promotes piecewise constant or linear solutions with minimum curvature as a more probable spatial constraint. Such regularizers are heavily used in various fields of image processing. They were only recently introduced in acoustics, where they have consistently proven to effectively model common structures. In this thesis, I propose to adapt the Schatten-norms of the Hessian as regularizers, which to the best of my knowledge has not been considered for acoustic holography yet. What is more, a fused approach is considered where additional sparsity is imposed on the spatial domain, suitable for the characterization of sparse and extended sources. A proximal splitting algorithm is adopted to solve the minimization problem, which allows an efficient implementation of the proposed regularizers. This work provides the fundamental understanding of derivative-based regularization and reveals its characteristics and abilities. The proposed methods are investigated and verified by numerical simulations and by using measurements obtained from an experimental setup. The required theory behind the algorithm is examined and a detailed exposition of its use is provided.
Supervisors Zotter, F., Höldrich, R.
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Derivative-Based Regulatisation of inverse problems in acoustic holography

Authors Pacher, S.
Year 2019
Thesis Type Bachelor's thesis
Topic Algorithmic Composition
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Alternative discretizations for the numerical evaluation of Rayleigh’s integral based on Fourier acoustics

Authors Pagavino, M.
Year 2019
Thesis Type Audio Engineering project
Topic Audio Signal Processing
Keywords acoustic holography
Abstract This audio engineering project deals with the numerial evaluation of sound fields from plane radiators, based on the spatial Fourier method. By the means of the fast Fourier transform it is possible to evaluate the Rayleigh integral at high computational efficiency, a feature that made the near field holography popular in its beginnings. Nowaday, efficiency of the implementation is not a pre-requisite anymore, but it could potentially be advantageous, therefore it is reconsidered in this work. The calculation in via the discrete wave-number domain implies: (i) by the discretization of the propagator, waves propagating in parallel to the radiating plane get singular at some frequencies, and (ii) the inherent spatial periodization of the sound source affects the waves propagating into directions inclined with regard to the plane by interference. The work shows up possible strategies to mitigate these effects. As a thinkable remedy concerning the singularity, a rectangular or triangular interpolant is proposed in 2D, and a trapezoidal one in 3D. The results of FFT-based holography are compared with the correct results of the discretized Rayleigh integral. Moreover, the effects of the alternative discretization interpolants are investigated concerning the inverse holographic problem. The results provided justify the question if, from today's perspective, the FFT-based nearfield acoustic holography is still meaningful, compared to the Rayleigh integral discretized in the space domain.
Supervisors Zotter, F.
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Process and Form in Feedback Systems

Authors Pozzi, D.
Year 2019
Thesis Type Master's thesis
Topic Algorithmic Composition
Abstract This thesis presents a model for computer music composition and performance - music instantiated during performance on the basis of stored programs and performance and environmental information. The model is proposed on a view of music composition as an experimental activity, whose results are the consequence of the manifold interactions happening amongst the various agencies involved in its development. In performing a retrospective analysis of one of the author’s most recent works (a live electronics performance entitled CK91) an attempt will be made at unfolding the underlying tapestry of strands and nodes that motivated its development and the choices taken along the way. Some threads and traces, which are considered relevant for their aesthetic and artistic implications, will also be pulled out of the experimental process and discussed from a critical perspective.
URL http://phaidra.kug.ac.at/o:91885
Supervisors Eckel, G.
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Artifices of interdependency

Authors Gagliardi, D.
Year 2019
Thesis Type Master's thesis
Topic Sound and Space
Keywords Dynamische Systeme
Abstract The Live Electronics paradigm in the field of Contemporary Music has often been oriented toward the description or the individuation of a relationship. When the act of composing relies on this practice, the exploration and the constitution of the role of each element which is active in such a network becomes the key of the resulting musical experience. This paradigm is hereby examined in a specific field of application: the relationship between the concrete acoustical world and its digital counterpart. This exploration begins with the definition and the interpretation of these terms, the acknowledgment of what the characteristic of a concrete object are, and the consequent delineation of the boundaries that constrain the concretization of the musical experience. The same importance is given to the description of the methodologies used in this process, which will allow the constitution of interconnections between the different elements. A minor but still relevant theme is the formalization of the performative solutions which will facilitate the listener to take part in the resulting sonic experience, by means of understanding which are the links, hence the forces, which reciprocally act on each other.
URL http://phaidra.kug.ac.at/o:91878
Supervisors Ciciliani, M., Eckel, G.
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ELSE: An Artistic Study on Algorithmic Agency in Sound Synthesis Composition

Authors Pozzi, D.
Year 2018
Thesis Type Computer Music project
Topic Algorithmic Composition
Abstract This article presents the development of a SuperCollider patch as a case study of the influence of algorithmic processes and algorithmic thinking in computer music practice. The crucial stages involved in the experimental design of a sound synthesis algorithm are analysed from a critical perspective that aims at exploring the multifaceted dynamics underpinning the relationship between artist and algorithmic process. In doing this, I’ll try to highlight the different agencies that contribute to shape the creative process of composing music with computers. It is suggested that the process of constant reconfiguration, intended as the iterative adaptation that takes place between an artist and the algorithms employed, has a major generative role in algorithmic practice. We may identify this generative element as one specific expression of the agency of the algorithmic. The case study is based on a retrospective documentation of Else, a generative algorithm conceived and realised in SuperCollider.
URL http://phaidra.kug.ac.at/o:77435
Supervisors Pirrò, D.
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Perceptually Motivated Ambient Scene Recording and Parametric Source Embedding

Authors Frauscher, E.
Year 2018
Thesis Type Master's thesis
Topic Audio Signal Processing
Keywords Spatial Audio
Abstract Various auditory experiments rely on the availability of highly authentic or highly plausible reference reproductions of real acoustic environments, for which the required capture, reproduction, and customization methods are investigated in this work. Most of the current approaches are based on simulated room impulse responses which allows a great freedom in customization; however, they can still be challenging as not all simulation settings will sound natural. As an alternative, this thesis targets a hybrid spatial recording and reproduction technique that allows to record real 3-dimensional acoustic scenes, and to customize them by parameterising embedded source material or the given recording by modifying its content. To preserve naturalness, parameterization requires to utilize estimated sound field parameters derived either from features captured in the recording environment or the recording itself. The proposed capture and parameterization approaches target loudspeaker-based reproduction. They are tested against reference dummy head and main microphone recordings in listening experiments to evaluate their authenticity and plausibility, among some relevant attributes.
Supervisors Zotter, F., Höldrich, R.
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Akustische Warnsignale und Verkehrslärmumgebung: Wiedererkennbarkeit und wahrgenommene Dringlichkeit von Fahrradklingeln

Authors Frohmann, L.
Year 2018
Thesis Type Bachelor's thesis
Topic Sonification
Keywords psychoacoustics
Abstract Raising awareness about how alarm sounds are perceived and evaluated by an individual in traffic scenery is important for developing new alarm designs, as well as for improving existing ones. Bearing a positive contribution to road safety, cyclists and pedestrians especially can benefit from appropriate alarming bell and horn sounds. This work focuses on the perception of urgency for various types of bicycle bells, as well as on acoustical descriptors influencing our judgement. The conducted listening experiments reveil the recognizability of bike bells among other everyday sounds and show urgency scores for testing in both silent surrounding and with additional traffic noise background. The results support a warning sound ranking in terms of efficiency and lead to an objective urgency model formed by spectral and temoral sound parameters.
URL http://phaidra.kug.ac.at/o:76982
Supervisors Höldrich, R., Weger, M.
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Optimum-phase primal signal and radiation-filter modelling of musical instruments

Authors Zagala, F.
Year 2018
Thesis Type Master's thesis
Topic Spatial Audio
Abstract Capture of musical instruments including directivity by spherically surrounding microphone array often leads to either overly complex radiation patterns or destructive interferences at high frequencies. There, small differences in the distance from the instrument to each of the microphones yield different arrival times in the captured signal and hereby large phase differences. Therefore, be it by linear triangular or spherical harmonics interpolation, frequency-independent directional interpolation of the microphone signals can result either in spectral degradation or in a shift of the signal energy to higher orders; especially affecting high frequencies. In this work, an analysis method is proposed in order to decompose directional signals of any measured instrument into an interference-free primal signal and a directivity filter. Both the directivity filter and the primal source signal utilise only the short-term spectral magnitude of each microphone signal in order to avoid artefacts. The magnitudes are complemented by a simplified phase using phase-retrieval techniques
URL http://phaidra.kug.ac.at/o:79029
Supervisors Höldrich, R., Zotter, F.
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Waterside - Die Entwicklung eines Audio Games

Authors Böhm, J.
Year 2018
Thesis Type Bachelor's thesis
Topic Algorithmic Composition
Abstract Diese Bachelorarbeit ist im Rahmen des Seminars ”Computermusik und Medienkunst“ zum Thema ”Audio Games“ entstanden. Im Unterschied zu traditionell eher visuell orientierten Computerspielen spielt in Audio Games der H¨orsinn eine zentrale Rolle. Im Zuge des Seminars wurde von jedem teilnehmenden Studierenden ein eigenes Audio Game konzipiert und als Prototyp implementiert. In dieser Arbeit werden zunächst Spiele im Allgemeinen – bis hin zu Audio Games im Speziellen – aus unterschiedlichen Perspektiven beleuchtet. Kern dieser Arbeit ist die Dokumentation des Designs und der Implementation eines Jump’n’Run Gehörbildungs-Lernspiels. Im Spiel – Waterside – werden auditiv vermittelte Aufgabenstellungen innerhalb einer zweidimensionalen Spielwelt durch ”physikalische“ Interaktion mit visualisierten Lösungsmöglichkeiten beantwortet. Die zu lösenden Aufgaben sind vom Seashore Test inspiriert und sollen eine spielerische Vorbereitung für diesen ermöglichen.
URL http://phaidra.kug.ac.at/o:76977
Supervisors Zmölnig, J.
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Multiband Compression for Ambisonics

Authors Huber, M.
Year 2018
Thesis Type Audio Engineering project
Topic Spatial Audio
Abstract Multiband compressors are known to serve as powerful and handy tools, and are frequently encountered within the mastering processing chain of audio productions. Yet up until now, no such tool existed in the world of multichannel 3D-audio formats like Ambisonics. This may be due to the high number of channels, entailing rather tough computational demands. The goal of this work is to discuss the stages involved in designing a multiband compressor and to relate the findings to a multichannel setting. In particular, crossover filter designs, perfectly reconstructing linear-phase systems, compressor designs and the encompassing computational requirements are reviewed. Additionally, a VST Plug-in has been developed over the course of this project, which has been released as part of the IEM Plug-in suite.
Supervisors Rudrich, D.
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game over

Authors Ressi, C.
Year 2018
Thesis Type Master's thesis
Topic Algorithmic Composition
Keywords Game, interaction, Open World
Abstract This paper deals with the question to what extent computer games can be seen as a distinct artistic medium and which possibilities they open for the creation of interactive audio-visual artworks. It is mainly based on the author's own work series called game over, providing various concrete examples for the specific properties of the medium: first of all the effects of constitutive, operational and implicit game rules on the play experience and the development of emergent, open forms, but also the formation of various virtual room experiences, the role of teleological strategies in terms of reward and punishment, and finally the construction and destruction of game worlds as a performative element and means of formal organization.
URL http://phaidra.kug.ac.at/o:76979
Supervisors Ciciliani, M., Utz, C.
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Influence of the form factor on the pitch of glides

Authors Kerle, L.
Year 2018
Thesis Type Bachelor's thesis
Topic Psychoacoustics
Keywords Frequency glides, sonification
Abstract This thesis deals with the investigation of the so-called glides. Glides are short sound impulses that change their instantaneous frequency either in ascending or descending direction and are characterized by their duration, by the frequency span the glide runs through and by the arithmetic mean of the frequency span. But this frequency span is not perceived for each glide. For glides with sufficiently small durations and frequency spans only one single pitch is evoked by the glide. This perceived pitch is not automatically the frequency at the temporal center of the glide. The larger the duration-bandwidth-product of the glide is, the higher is the tendency to perceive a pitch near the final frequency of the glide. To investigate the perceived pitch a listening experiment is carried out in which various glides with different durations, bandwidths and arithmetic center frequencies are tested. But before the listening experiment is described, a short review of the existing literature and the found facts will be given. Subsequently the listening experiment is described in which various form factors were examined. These form factors influence the course of the instantaneous frequency. For various form factors two glides with identical duration, arithmetic center frequency and bandwidth but different direction are compared to each other. It is the main objective of this thesis to find a certain form for the up-glide and the down-glide to perceive the same pitch for both glides. Afterwards a statistical analysis is carried out to show the significance of the achieved results. In conclusion further investigations are explained that could be carried out based on the obtained outcome.
URL http://phaidra.kug.ac.at/o:76978
Supervisors Höldrich, R.
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Sound Event Detection for Smart Cars

Authors Linke, J.
Year 2018
Thesis Type Master's thesis
Topic Audio Signal Processing
Keywords Music Information Retrieval, Neuronal Networks
Abstract This thesis designs classification models from the area of artificial intelligence to distinguish between urban noise and siren sounds. Audio recordings from the urban environment and audio recordings capturing specific sound events are collected in a basic data set. With audio signal processing suitable audio features for four classification approaches are extracted and selected from the obtained data environment. Different machine learning classification algorithms are discussed for two classification tasks: Two approaches for a binary classification task and one approach for a classification task with three classes are presented. The last approach compares the best binary classification solution with a deep learning classifier in the sense of transfer learning. All classification models are tested with a self-recorded validation set including car microphone recordings from the urban environment and the so-called Martinshorn.
Supervisors Sontacchi, A.
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Sonifikation von Flugverkehrsdaten

Authors Kerber, J.
Year 2018
Thesis Type Audio Engineering project
Topic Audio Signal Processing
Abstract follows
Supervisors Weger, M.
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Plug-In for Frequency-Dependent Control of Microphone Polar Patterns.

Authors Deppisch, T.
Year 2018
Thesis Type Audio Engineering project
Topic Audio Signal Processing
Abstract Arbitrary first-order polar patterns can be created by weighted summation of the outputs of front and back diaphragm of a dual-diaphragm microphone. If the output signals of both diaphragms are accessible inside a digital audio workstation (DAW), the polar pattern can be (re)adjusted at any time and is not limited to discrete, predefined patterns. This work describes the development of an open-source software plug-in, which allows for the frequency-dependent control of a dual-diaphragm microphone's polar pattern in up to five adjustable frequency bands. Two approaches for creating the underlying filterbank are presented: A linear-phase FIR approach and an IIR approach. Diffuse-field and free-field equalization of synthesized polar pattern signals are described exemplarily for a particular microphone and an algorithm for automatic polar pattern optimization is designed, based on the intensity of a target signal. The characteristics of dual-diaphragm microphones are investigated by employing a physical model. Filters for equalization of the proximity effect are derived by this model.
Supervisors Frank, M.