Søren Krarup Olesen

Beaming teching application: recording techniques for spatial xylophone sound rendering

BEAMING is a telepresence research project aiming at providing a multimodal interaction between two or more participants located at distant locations. One of the BEAMING applications allows a distant teacher to give a xylophone playing lecture to the students. Therefore, rendering of the xylophone played at students location is required at teachers site. This paper presents a comparison of different recording techniques for a spatial xylophone sound rendering. Directivity pattern of the xylophone was measured and spatial properties of the sound field created by a xylophone as a distributed sound source were analyzed. Xylophone recordings were performed using different microphone configurations: one and two-channel recording setups are implemented. Recordings were carried out in standard listening room and in an anechoic chamber. Differences between anechoic and reverberant xylophone sound for binaural synthesis are examined. One-channel recording approach with binaural synthesis for spatial xylophone so...

Evaluation of dynamic binaural reproduction system for live transmitted xylophone recording

For a special teaching application of the telepresence research project BEAMING, a scenario of a remote teacher (the Visitor) teaching a local student to play a xylophone through an embodiment is defined. In order to achieve this, a system is required to record, transmit and render the sound of the xylophone to the teacher in a dynamic scene. In an implementation of such a system, the xylophone is recorded using a mono recording technique. The signal is then processed to spread out the sound of the distributed sound source as multiple point sources in the virtual scene experienced by the Visitor. Finally head tracking allows for a dynamic binaural rendering of the xylophone sound. The goal of this paper is to evaluate the realism of this virtual (auditory) representation of a real xylophone. A listening test is designed to compare characteristics of a real physical xylophone in front of the listener with a rendering using the described system. The evaluation is done with a basis in methods previously used...

Calibration aspects of binaural sound reproduction over insert earphones

Earphones are nowadays widely adopted for the reproduction of audio material in mobile multimedia and communication platforms, e.g. smartphones. Reproduction of high-quality spatial sound on such platforms can dramatically improve their applicability, and since two channels are always available in earphone-based reproduction, binaural reproduction can be applied directly. This paper is concerned with the theoretical and practical aspects relevant to the correct reproduction of binaural signals over insert earphones. To this purpose, a theoretical model originally developed to explain the acoustic transmission to and within the open ear canal is revisited [Mo/ller, Appl. Acoust., 36, 171-218 (1992)]. The model is modified accordingly in order to investigate the aspects of the transmission within the blocked ear canal that are significant to the calibration required to preserve the natural spatial cues that exist during normal hearing conditions, i.e. during an open-ear-canal situation. To evaluate the vali...

A Cubical Approach To The Ray-tracing Algorithm

A cubical approach to the ray-tracing algorithm of room simulation will be presented. The algorithm has been optimised to meet the strict demand for real-time processing with aspect to virtual reality audio. The basic idea is to improve calculation speed at the expense of accuracy. Assuming that the auditory system is only vaguely affected by the arrival time of a certain wall reflection the entire model can be discretised into a finite number of cubes, that is, describing the sound source, sound receiver and every point and material in the room as a cube with certain characteristics. Currently the algorithm is implemented on a PC, however, it is expected to be finally implemented on a fixed point digital signal processor. The PC program shows a speed improvement of at least twenty times compared to the calculation speed of traditional raytracing. The algorithm or at least the idea is expected to be used in future virtual reality set-ups and merged with e.g. finite difference methods

Subjective evaluation of space discretized ray-tracing

The growing interest in multimedia raises questions like how to present 3‐D sound to the user of a multimedia system. Such presentations should not necessarily be exact replicas of the real‐life experiences; however, they should still provide a quality that convinces the user of being present in the acoustical environment intended. This paper briefly introduces an alternative method of ray tracing that indeed is simplified compared to that of the conventional ray‐tracing/mirror‐image approach. The method may be considered as a space discretized version of ray tracing and it is considerably faster than the latter. In order to reveal subjective differences between the two methods, a psychoacoustical listening experiment was carried out using binaural synthesis. Twenty subjects participated and in two sessions they were asked to rate coloration and reverberation, respectively, by clicking a mouse—each time listening to a music or speech sound frame. In a third session a sketch of a room and the position of t...