Download Realization of Vold-Kalman tracking filter. A least squares problem The aim of this work was the implementation of the so-called VoldKalman filter. This filter was introduced by Vold and Leuridan in 1993 [1], it is a heterodyne filter for tracking the sinusoidal components of a noisy signal. The formulation of the Vold-Kalman filter leads to a least squares problem. The great advantage of this time-varying filter is that all sinusoids of a signal can be extracted simultaneously yielding a suppression of beating phenomena of close or crossing frequency trajectories. In this paper, we propose a realization for offline processing using the preconditioned conjugate gradient method. Furthermore, we present trivial expressions for the bandwidth and the transition time of first and second order filters.
Download Multichannel sound reproduction system for binaural signals - the ambisonic approach Convincing sound reproduction via headphones requires filtering of virtual sound sources with head related transfer functions (HRTF). HRTFs describe signal differences at the two ear drums in level, time and frequency weighting [1,2]. Another psychoacoustic phenomenon of the human auditory system concerning hearing in natural sound fields is the improvement of source localization if small head movements are possible [3]. In this paper a computational efficient implementation to get dynamic binaural signals (in dependence on the head position) is proposed. This realtime modell is based on Ambisonic sound reproduction [4,5].
Download Analysis, resynthesis and interpolation of the interior noise of a car The aim of this work was to develop a realtime simulator for vehicle interior noise in varying load situations. Using this simulator, laboratory hearing tests which are common in the automotive industry may be executed more realistically than by using recorded sounds without any interaction possibility. A simplified model for the load situation of a car is presented. Using this model, the interpolation between the prerecorded signals is performed to obtain signals for other load situations. Furthermore, an analysis/resynthesis system for the interior noise of cars is introduced which only needs a sparse set of parameters.
Download Further Investigations On 3D Sound Fields Using Distance Coding This investigation proposes a possibility to synthesise a true 3D sound field over loudspeakers. A new approach concerning the distance coding is presented. We tried to combine the benefits both using the Wave Field Synthesis (WFS) approach and Higher Order Ambisonics (HOA). Therefore the proposed system can be divided into two main parts. Firstly the determination of the driving functions of the sound sources using the WFS approach. Secondly the coding for transmission or storage whereby the scheme is based on the Ambisonics approach using higher orders. The paper is organised in three sections. The first section gives a brief introduction about the WFS and the HOA approaches. In the second section the derivation of the driving functions is presented and the coding scheme of the derived source signals is explained. Finally the paper is concluded and further possible research directions are identified.
Download Room simulation for binaural sound reproduction using measured spatiotemporal impulse responses In binaural sound reproduction systems the incorporation of room simulation is important to improve sound source localisation capabilities. Thus, the localisation error can be decreased, while equivalently an enhanced externality (out of head localisation) is achieved. Previously proposed works are based on simple geometrical approaches for room simulation. In this paper an alternative method using measured room impulse responses (RIRs) is presented. Therefore, it is possible to obtain a convincing acoustical image of an existing room. The RIRs are measured using a circular microphone array to capture both temporal and spatial information of the desired room.
Download Spatial Auditory Displays - A study on the use of virtual audio environments as interfaces for users with visual disabilities This paper presents the work on a prototype spatial auditory display. Using high-definition audio rendering a sample application was presented to a mixed group of users with visual disabilities and normal sighted users. The evaluation of the prototype provided insights into how effective spatial presentation of sound can be in terms of human-computer interaction (HCI). It showed that typical applications with the most common interaction tasks like menus, text input and dialogs can be presented very effectively using spatial audio. It also revealed that there is no significant difference in effectiveness between normal sighted and visually impaired users. We believe that spatial auditory displays are capable to provide the visually impaired and blind access to modern information technologies in a more efficient way than common technologies and that they will be inevitable for multimodal displays in future applications.
Download A library for realtime 3D binaural sound reproduction in pure data(PD) This paper presents a library for programming 3D binaural sound reproduction systems using Pure Data (pd), an open source computer music programming language. The theory that forms the basis of the proposed library is an improved virtual Ambisonics approach. Using this approach provides computationally efficient implementation of multiple moving sound sources, room simulation, head tracking and time varying listener positions in virtual space. Furthermore, simple GUI objects for controlling parameters are implemented to provide easy to use environment.
Download An auditory 3D file manager designed from interaction patterns This paper shows the design, implementation and evaluation of an auditory user interface for a file-manager application. The intention for building this prototype was to prove concepts developed to support user interface designers with design patterns in order to create robust and efficient auditory displays. The paper describes the motivation for introducing a mode-independent meta domain in which the design patterns were defined to overcome the problem of translating mainly visual concepts to the auditory domain. The prototype was implemented using the IEM Ambisonics libraries for Pure Data to produce high quality binaural audio rendering and used headtracking and a joystick as the main interaction devices.
Download Effect of augmented audification on perception of higher statistical moments in noise Augmented audification has recently been introduced as a method that blends between audification and an auditory graph. Advantages of both standard methods of sonification are preserved. The effectivity of the method is shown in this paper by the example of random time series. Just noticeable kurtosis differences are effected positively by the new method as compared to pure audification. Furthermore, skewness can be made audible.
Download Directivity Patterns Controlling the Auditory Source Distance What influence does the directivity of a sound source have on the perceived distance impression in a room? We propose different directivity pattern designs able to modify the auditory source distance. The idea is accompanied with a comprehensive experimental study investigating the audio effect and its behavior by auralization of directional sound source and room using a 24-channel loudspeaker ring inside an anechoic chamber. In addition to the proposed directivity designs, the study covers influence of auralized room, source-to-receiver distance, signal, and single-channel reverberation. Moreover, simple room acoustical measures perform well in predicting the new effect.