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Akustik-Blog

Kolloquium

Nov
9
Fr
Shaima’a Doma: Development of a demonstration and evaluation tool for individualized binaural technology
Nov 9 um 11:00 – 12:00

The transfer function from an arbitrary source position to the ear canal entrance is characterized by typical interactions with head, pinna and torso geometry. This highly individual filtering of sound is described by the head-related transfer function (HRTF) and is essential for a realistic spatial auditory reproduction.

Obtaining individual HRTFs of high quality, however, requires specialized equipment that is not widely available. In some cases, it has shown to be particularly difficult, e.g. for children, whose movement during the measurement leads to inaccurate results.

Individualized HRTFs offer a compromise by making modifications to a given non-individual HRTF set. Over the past years, various approaches have been discussed, such as individualization of the Interaural Time Difference (ITD), frequency scaling or methods based on Principal Component Analysis (PCA). These methods use anthropometric dimensions to estimate a subject’s individual HRTF. The dimensions can, for instance, be obtained from 3D images generated by structured light scanners or magnetic resonance imaging (MRI).
In this thesis, a demonstration tool is developed. With this tool, a direct auralization is possible, whilst manipulating parameters of several of the aforementioned HRTF individualization methods. Using a set of exemplary virtual acoustic scenes, the user can modify a provided HRTF set and observe the resulting differences. The tool shall find application in the subjective evaluation and optimization of HRTFs.
A listening test is further conducted, investigating just noticeable differences (JNDs) in anthropometric measures, which are used in the demonstration tool as part of the reconstruction of HRTFs from principal components. Suitable step sizes for tunable parameters in the tool are derived from the results.

Nov
16
Fr
Daniel Filbert: Filter design of diffraction in auralization of urban environments
Nov 16 um 11:00 – 11:30

The acoustic propagation of sound in the open field or in the interior can be calculated effectively and in high quality by geometric simulation methods. However, phenomena that are mainly due to wave-based properties are implemented insufficiently or only with comparatively complex calculation models by these approaches.
In this bachelor theses, well-known methods for the filter design of diffraction simulation in geometric acoustics will be investigated and applied for the auralization of urban environments, in which mainly wave fronts of low order come to account.

Du Bokai: Sound field reproduction with HOA using directivity loudspeakers
Nov 16 um 11:30 – 12:00

Sound reproduction is an important aspect in spatial audio, where not only the audio content but also the spatial properties of the reproduced to create an immersive experience. I am a visiting PhD student from Northwestern Polytechnical University in China. This talk will include a brief introduction to my university and important methods used in sound field reproduction. Some of my work on sound field reproduction using high order ambisonics(HOA) method will also be presented.

Nov
30
Fr
Johannes Imort: The Directional Energy Decay Curve in Reverberation Rooms
Nov 30 um 11:00 – 11:30
To describe acoustical absorption properties of  materials, the random incidence absorption coefficient is to be measured, which is done in a reverberation room and require the sound field to be diffuse. Earlier studies showed poor results in reproducibility of these measurements among laboratories, so there is reason to suspect, that the errors result from the missing condition of a diffuse sound field. A standardized method to characterize the diffuseness is lacking.
This thesis evaluates the concept of directional energy decay curves to obtain informations about systematic defects in the isotropy of a sound field. Therefore different acoustic simulations were conducted, evaluated and put in context with the absorption coefficient calculation according to ISO 354.