Kolloquium
A powerful and flexible approach to record or encode a spatial sound
scene is through spherical harmonics (SHs), or Ambisonics. An SH-
encoded scene can be rendered binaurally by applying SH-encoded
head-related transfer functions (HRTFs). Limitations of the recording
equipment or computational constraints dictate the spatial reproduc-
tion accuracy, thus rendering might suffer from spatial degradation
as well as coloration. This paper studies the effect of tapering the
SH representation of a binaurally rendered sound field in conjunction
with its spectral equalization. The proposed approach is shown to
reduce coloration and thus improves perceived audio quality.
This thesis consists of a study with adults in relation to educational institutions with the aim to evaluate speech perception and listening effort depending on the noise condition.
For this purpose three different noise conditions were simulated: speech-shaped noise (SSN), which is characterized for having a similar spectrum as the average long-term spectrum of a speech signal and is considered to be the most effective energy masker of speech; irrelevant and relevant multi-talker babble (IMTB and RMTB, respectively), which consists of several people simultaneously talking in a foreign language for the listener, in IMTB, or in the same or similar language, in RMTB.
These noises were included individually as background noises in a dual-task listening experiment. The first task consisted of the measurement of time response and percentage of correct words, where participants had to identify stimuli word and select the corresponding image between four possible options (e.g. Kopf – Topf – Zopf – Frosch). Then, the second task focused on the measurement of reaction time after a visual stimulus, in which participants had to press a button when the light bulb in the screen turned on.
This experiment tested a total of 24 conditions by modifying signal-to-noise ration, target and distractor position combination and type of noise.
In the built environment, there is a concern about steadily growing high annoyance due to noise in private dwellings as well as in commercial work sites that leads towards reduced power of concentration during physical or mental work, and disturbance of sleep. The studies show that people are exposed to the noises from neighbours which causes consequences of disturbances in communication and sleep, physical or mental work imparities, and the disturbances in conversation or listening to the TV or radio in private dwellings as well as communication in office premises.
There exist different standards that describe the performance of buildings in terms of sound level reduction indices in the form of a single number value and/or frequency dependent curves, however, it can be assumed that these quantities are insufficient to describe the real situation for the perception of noise. Therefore, there is an opportunity in developing a novel real-time building acoustics auralization platform based on detailed models of ISO standards and available measurements, integrated with virtual reality (VR) systems, to accurately realize the perception and evaluation of noise and comfort.
The auralization of sound insulation between the adjoining rooms in VR-environments describes the sound transmission between enclosures, where sound insulation prediction methods are applied for a high quality auditory stimuli. In this context, a real-time building acoustic auralization framework in 3D audio-visual technology is the aim of our research project to introduce more realism and contextual features into psychoacoustic experiments.
The research focuses on describing the design and implementation of this framework that is a vital part of 3D-immersive sound rendering VR-Systems. This auralization framework relies on up-to-date knowledge of building acoustics techniques and enables a physically accurate airborne sound insulation auralization in virtually constructed environments, including important effects such as sound transmission, bending wave effects, source directivities, and source/receiver room acoustics. In spite of this realistic sound insulation rendering between adjoining rooms, not only the indoor sources are supported at runtime, but also outdoor moving sources such as vehicles.
In this way, a real-time auralization framework is possible to analyse the performance of building elements and to evaluate the noise and comfort levels for building structures in an authentic manner in real-time. This framework would allow the test subjects to perform any task of daily life of work or learning under conditions of usual behaviour and movement. Therefore, it is intended to create more realistic noise perception tests in real-time virtual reality environment than simply asking for “annoyance” in questionnaires in listening tests.
As I am interested in acoustical and tele-communicational devices, I chose Head acoustics GmbH as the place for my 18-weeks mandatory internship so that I can have insight into practical engineering application in acoustical and signal processing area. Head acoustics is one of the worldwide successful companies in integrated acoustics solution as well as communication technology. In this time, I worked in the Telecom Division and my main task is to measure the Mean Opinion Score (MOS) of two VoIP devices with few of our Measurement Front-ends (MFE), including preparing and designing measurements under different network conditions using measurement system ACQUA. Additionally, I have also worked for the assistance of measurement data processing and visualization with Python libraries Pandas and Matplotlib.
Im alltäglichen Arbeiten sind Menschen von verschiedenen Geräuschen bzw. Lärm umgeben, die sich maßgeblich auf die kognitive Arbeitsleistung und die akustische Zufriedenheit auswirken können. Diese akustische Wahrnehmung und ihre Auswirkung werden von verschiedenen Faktoren verursacht und beeinflusst. Daher wird eine vielfältige akustische Raumanalyse, sowohl vom objektiven, als auch vom subjektiven Aspekt, benötigt. In dieser Masterarbeit werden Großraumbüros mit gehörrichtigen Verfahren vermessen und deren akustische Eigenschaften analysiert. Zum einen wird die Raumakustik der Räume untersucht, zum anderen werden die Hintergrundgeräusche in Anwesenheit von Personen für die psychoakustische Analyse gemessen (In situ-Messungen). Dabei wird der ITA-Kunstkopf verwendet, um eine gehörrichtige Auswertung zu erhalten. Zusätzlich wird die subjektive Wahrnehmung untersucht, indem Frageböge an die anwesenden Personen in den Räumen verteilt werden, und während der In situ-Messungen bearbeitet werden. Anschließend werden die Relationen zwischen Raumakustik- und Psychoakustikparameter, sowie zwischen objektiven und subjektiven Ergebnissen ausgewertet.
