October 2024 - Kommunikationstechnik-Kolloquium

Communication Technology Colloquium at IKS - Einladung Promotionsvortrag
by Anett Schindler 29 Oct '24

29 Oct '24

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquium. *Thursday, November 14, 2024* *Speaker*: Sebastian Nagel, M. Sc. *Topic*: Interactive Reproduction of Binaurally Recorded Signals *Time:* 11:30 a.m. *Location*: hybrid - Lecture room 4G *Online*: https://rwth.zoom.us/j/61215027648?pwd=MTJvayt5bkdka04raWZVempPZGE0Zz09 Meeting-ID: 612 1502 7648 Passwort: 380386 Abstract of the Dissertation *Interactive Reproduction of Binaurally Recorded Signals * by Sebastian Nagel, M.Sc. Motivation, Goal, and Task of this Dissertation The goal of acoustic augmented or virtual reality is to artificially invoke a realistic auditory impression in the listener. One technique to achieve this goal is /binaural reproduction/, which refers to the reproduction of certain audio signals at the two ears of the listener. The ear signals can be obtained by /binaural recording/ or /binaural rendering/, that is, by spatially sampling a real or virtual sound field with two microphones, one at each ear of a recording head. Such signals are referred to as /binaurally recorded signals/ in the following. For a moving listener to perceive sound sources as fixed in the environment, the reproduced signals need to match the listener’s movements. State-of-the-art methods for this /interactive binaural reproduction/ generate such signals based on denser spatial samplings of sound fields (i.e., more than two microphones), or they perform real-time binaural rendering. The goal of this thesis is to achieve interactive binaural reproduction based on binaurally recorded signals, that is, on two ear signals originally intended for non-interactive binaural reproduction for a non-moving listener. This is desirable for two major reasons. It makes binaural recordings usable for immersive playback. This potentially improves the user experience in applications such as telecommunications, or for consumer-generated content, where greater technical effort for recording may not be feasible. Furthermore, the resulting methods seamlessly interoperate with established technologies. Technically, binaurally recorded signals are ordinary stereo signals, and their spatial relationships are defined by human anatomy. This eliminates the coordination and standardization efforts that would be required to make the state-of-the-art methods widely usable. The task of this dissertation is to develop algorithms that interact with a complex biological system (the human auditory system). The ultimate evaluation criterion is the subjective quality of the listening experience to the human listener, which can only be assessed through listening experiments. Therefore, to validate the result, a listening experiment is presented at the end of the dissertation. Before that, algorithms are developed and evaluated on a theoretical basis. Derivations are based on signal models, and evaluations are based on the interpretation of signal properties, both of which are rooted in knowledge of human auditory perception. Major Scientific Contributions The model-based algorithms are developed in two steps. First, binaurally recorded signals with only coherent sound from a single sound source are regarded. The derived algorithms act as a time-variant filter to modify the spatial properties of the binaurally recorded signals. The filter is parameterized with the measured listener head motion and the source direction estimated from the recorded signals. This novel principle allows the listener to perceive the source in a stable position in the environment. It was first proposed by the author in [NJ18], and it has been patented [NJ23]. This dissertation provides analyses of different filter design methods and architectures. The subjective quality of the first algorithms is not suitable for signals which violate the model assumption of only direct sound, such as reverberant signals. Therefore, signals with a mix of coherent and incoherent sound are regarded in the second step. The derived algorithms perform a coherence-adaptive trade-off between the spatial modification of the coherent sound and the preservation of incoherent sound [NHJ20]. Their performance is theoretically limited by the limited ability of linear spatial filters to separate coherent and incoherent signal components [NJ21]. This dissertation provides a thorough analysis of the theoretical limitations. It also proposes perceptually motivated improvements to the filter structure that significantly extend the theoretical limits. Finally, this dissertation presents a listening experiment to validate the proposed method. Acoustic scenes with speech sources were binaurally recorded at the ears of human test subjects. A real-time prototype with head tracking provided interactive binaural reproduction of these recordings via headphones. Subjects were asked to distinguish, in an indirect comparison, the artificial binaural reproduction from reality (ground-truth signals emitted by the loudspeakers in the same room). Results show that this task was difficult even for expert listeners, indicating that the method provides a natural and plausible listening experience. Major Publications [NJ18] S. Nagel and P. Jax, “Dynamic Binaural Cue Adaptation,” in Proceedings of International Workshop on Acoustic Signal Enhancement (IWAENC), September 2018. [NHJ20] S. Nagel, D. Haupt, and P. Jax, “Coherence-Adaptive Binaural Cue Adaptation,” inProceedings of International Conference on Audio for Virtual and Augmented Reality (AVAR), August 2020. [NJ21] S. Nagel and P. Jax, “On the Use of Additional Microphones in Binaural Cue Adaptation,” in Proceedings of ITG Conference on Speech Communication, September 2021. [NJ23] S. Nagel and P. Jax, “Methods for obtaining and reproducing a binaural recording,” U.S. patent, US 11,546,703 B2, January 2023. All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of dates of the Communication Technology Colloquium can be found at: https://www.iks.rwth-aachen.de/aktuelles/kolloquium Best regards Anett Schindler *Anett Schindler* Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 schindler(a)iks.rwth-aachen.de https://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Anett Schindler 08 Oct '24

08 Oct '24

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquium. *Monday, October 14, 2024* *Speaker*: Johannes Hahn *Time:* 14:00 pm *Location*: hybrid - Lecture room 4G and https://rwth.zoom.us/j/61215027648?pwd=MTJvayt5bkdka04raWZVempPZGE0Zz09 Meeting-ID: 612 1502 7648 Passwort: 380386 *Master-Lecture: ** * */*Identification of Time-Variant MIMO Systems using Acoustic Manifolds*/* Many applications in digital signal processing such as Acoustic Echo Cancellation (AEC) and adaptive Crosstalk Cancellation (CTC) rely on methods of Acoustic System Identification (ASI), which aims at determining the impulse responses between loudspeakers and microphones in a given acoustic enclosure. This task is particularly challenging if multiple inputs and outputs have to be considered, leading to a large number of parameters to be identified. The complexity increases further if the system and thus the parameters are time-varying. Moreover, such Multiple Inputs Multiple Outputs (MIMO) systems suffer from the non-uniqueness problem, which impairs the performance of established ASI methods. To overcome these challenges, recent developments focus on the incorporation of prior knowledge into the system identification. In this context, several approaches take advantage of the manifold hypothesis. It states that the Room Impulse Responses (RIRs) in a given MIMO scenario can be modeled by a low-dimensional representation lying on or close to a usually nonlinear manifold, which can be learned a-priori or estimated online. This thesis investigates a novel approach to the identification of time-variant MIMO systems which exploits the manifold hypothesis to greatly reduce the number of tracked parameters. A Variational Auto-Encoder (VAE) is trained to learn the manifold in terms of a low-dimensional coordinate representation. During ASI, only this representation is tracked, using an Extended Kalman Filter (EKF). As a result, less time-variant parameters have to be identified. Additionally, measurements are conducted using an artificial head and two loudspeakers to create a data set of real-world RIRs, and test sequences are recorded that facilitate the evaluation of ASI algorithms in a real-world scenario. In an extensive parameter study, the architecture and hyperparameters of the VAE are investigated and tuned. A validation of the proposed method in simulated scenarios as well as on the test recordings showcases its superiority in the identification of time-varying systems and its robustness towards the non-uniqueness problem in comparison to established ASI methods and related approaches built on the manifold hypothesis. All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of dates of the Communication Technology Colloquium can be found at: https://www.iks.rwth-aachen.de/aktuelles/kolloquium Anett Schindler Institute of Communication Systems(IKS) Prof. Dr.-Ing. Peter Jax RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany <https://www.google.com/maps/search/Muffeter+Weg+3a,+52074+Aachen,+Germany?e…> +49 241 80 26958(phone) +49 241 80 22254(fax) schindler <mailto:sedgwick@iks.rwth-aachen.de>@iks.rwth-aachen.de <mailto:sedgwick@iks.rwth-aachen.de> https://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Anett Schindler 07 Oct '24

07 Oct '24

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquium. *Friday, October 11, 2024* *Speaker*: Lea Brehm *Time:* 11:00 am *Location*: hybrid - Lecture room 4G and https://rwth.zoom.us/j/61215027648?pwd=MTJvayt5bkdka04raWZVempPZGE0Zz09 Meeting-ID: 612 1502 7648 Passwort: 380386 *Bachelor-Lecture: ** * */*Evaluation of Sound Source Localization Algorithms with Recorded Binaural Signals*/* /The localization of binaural sound sources is essential for various modern applications. While most algorithms struggle with dynamic situations caused by the movement of the head, the movement invariant beamforming binaural direction of arrival estimator (MIBF DoA estimator) involves the information on head rotations. This algorithm applies the motion information to a target beamforming direction-of-arrival (DoA) estimator in order to identify the position of a sound source on the horizontal plane in dynamic situations./ /This thesis implements an extension of this algorithms to three dimensions, achieved by the usage of quaternions for the MIBF DoA estimator. We evaluate the algorithm based on simulations and data from an experimental set up. The results demonstrate that the algorithm identifies sound source positions in the three dimensional space correctly, especially during the movement of the head around multiple rotation axes. Furthermore, the utilization of head motions resolves problems caused by an ambiguous interaural time difference (ITD) and interaural level difference (ILD)./ / / All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of dates of the Communication Technology Colloquium can be found at: https://www.iks.rwth-aachen.de/aktuelles/kolloquium Anett Schindler Institute of Communication Systems(IKS) Prof. Dr.-Ing. Peter Jax RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany <https://www.google.com/maps/search/Muffeter+Weg+3a,+52074+Aachen,+Germany?e…> +49 241 80 26958(phone) +49 241 80 22254(fax) schindler <mailto:sedgwick@iks.rwth-aachen.de>@iks.rwth-aachen.de <mailto:sedgwick@iks.rwth-aachen.de> https://www.iks.rwth-aachen.de/

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