- Kommunikationstechnik-Kolloquium - lists.rwth-aachen.de

Communication Technology Colloquium at IKS
by Irina Ronkartz 16 Jun '21

16 Jun '21

Dear subscribers of the colloquium newsletter, we are pleased to announce the next date of our Communication Technology Colloquium: *Wednesday, June 23, 2021* *Speaker:* Markus Tilichi *Tim*e: 11:00 a.m. *Location*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master-Lecture*: Enhanced Own Voice Perception for Hearables Using Machine Learning Modern headphones implement sophisticated signal processing and control algorithms to improve the user’s hearing and listening experience. Especially new generation in-ear headphones, so-called hearables, integrate these technologies, such as active noise control, on a large scale. A remaining issue with hearables is the sound degradation introduced through sealing the ear canal. This degradation is called the Occlusion Effect. It is often described as boomy and hollow perception of the speaker’s own voice. While Active Noise Cancellation reduces ambient noise, the Occlusion Effect still persists. In order to improve the speaker’s own voice perception and alleviate the Occlusion Effect, it is required to play back some of the voice signal without amplifying ambient noise. In this thesis a novel approach for selective hear-through based on deep neural networks is investigated. Integrated into a feed-forward ANC topology the proposed neural network utilizes ambient and in-ear microphone signals for an estimation of the speaker’s own voice. Speech samples for both microphone signals were simulated through augmentation of the DARPA TIMIT speech corpus. This included virtually occluding the samples for one channel and adding real-world noise samples to the other. The proposed network was found to reduce ambient noise from the test dataset to a barely audible extent. Metrics for quality and intelligibility suggest superior denoising performance in comparison with one channel network benchmarks. Despite the relatively small training dataset, the network may also regularize well when trained with measurement data. All interested parties are cordially invited, registration is not required. General information about the colloquium, as well as a current time scale of the Communication Technology Colloquium can be found at: https://www.iks.rwth-aachen.de/atktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 14 Jun '21

14 Jun '21

Dear subscribers of the colloquium newsletter, we are pleased to announce the next date of our Communication Technology Colloquium: *Monday, June 21, 2021* *Speaker:* Henning Niendieck *Time:* 2:00 p.m. *Location*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master-Lecture*: Optimized Design of an Acoustic Front-End for Active Noise Cancelling Headphones Headphones with active noise cancelling (ANC) capability become more and more common in everyday life. The acoustic front-end, consisting of the headphone enclosure, a speaker and at least two microphones, is a crucial part of the ANC system. It significantly influences the achievable degree of noise cancelling. The optimization of the acoustic front-end is therefore a key factor for a high ANC performance. Being able to completely predict the influence of every element of the acoustic front-end is a desirable goal. This work comprises an investigation of the different components of the acoustic front-end. It includes the characterization of a set of microphones to evaluate the influence on the ANC performance. A development of a model of the electro-acoustic system of a headphone enclosure with an integrated dynamic speaker allows the simulation of relevant transfer paths. Every individual element of the enclosure is modeled, so that the effect of every parameter on the transfer paths can be investigated. This provides a great advantage over investigations on the basis of measurements. A comparison of the boundary element method and lumped element method shows their suitability for acoustic modeling. The inability of the used implementation of the boundary element method to directly model viscothermal losses exhibits limitations, as these losses play an important role in the acoustic front-end. A 3D print of the prototype allowed the verification of the acoustic model with measurements. The different enclosure design parameters with regard to ANC performance were studied on the bases of both, simulations and measurement. An improvement of the prototype could be achieved by damping resonances. This reduces group delay in the path between the speaker and the inner microphone, which is an important limiting factor for ANC. The group delay of the inner microphone was found to be significant for low frequencies. The investigations deliver valuable knowledge about the influence of the different parameters of the acoustic front-end on the important factors for ANC. An acoustic model was obtained that allows the prediction of various transfer paths and an easy fine tuning of the elements of the acoustic front-end. All interested parties are cordially invited, registration is not required. General information about the colloquium, as well as a current time scale of the Communication Technology Colloquium can be found at: https://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 10 Jun '21

10 Jun '21

Dear subscribers of the colloquium newsletter, we are pleased to announce the next date of our Communication Technology Colloquium: *Thursday, June 17, 2021* *Speaker*: Daniel Gotzens *Time*: 11:00 a.m. *Location*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Bachelor Lecture*: Real-Time Own Voice Estimation for Hearables Utilizing Multiple Microphone Signals Hearable devices employ several microphones to be used in telecommunication applications as well as for active noice cancellation. It is proposed that the signals generated by these microphones can be combined into an accurate and low-interference estimate of the user's own voice in real time by using digital beamforming algorithms, namely the so-called delay-and-sum and minimum variance distortionless response beamformers, especially in conjunction with additional filtering in the shape of a bandpass or a Wiener filter. To test this, several input samples are recorded on a hearable device and then processed with said algorithms. It is found that it is indeed possible to generate such a signal using the proposed algorithms, improving the signal to noise ratio by several decibels while maintaining a low distortion of the speech signal. All interested parties are cordially invited, registration is not required. General information about the colloquium as well as a current time scale of the Communication Technology Colloquium can be found at: https://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Kommunikationstechnisches Kolloquium am IKS
by Irina Ronkartz 27 Apr '21

27 Apr '21

Sehr geehrte Abonnenten des Kolloquium-Newsletters, gerne informieren wir Sie über den nächsten Termin unseres Kommunikationstechnischen Kolloquiums. *Montag, 3. Mai 2021* *Vortragender*: Yannick Fleischmann *Zeit:* 14:00 Uhr *Ort*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master-Vortrag*: Nachbildung von Körperschall in Ohrsimulatoren Das tragen von Ohrhörern oder Hörgeräten führt durch den Verschluss des Ohrkanals zu einer veränderten Stimmwahrnehmung. Diese wird hervorgerufen durch die Einstrahlung von Körperschall durch die Ohrkanalwände. Stetig zunehmende Rechenleistung in immer kleineren Formaten ermöglicht immer komplexere Methoden zur aktiven Störgeräuschunterdrückung, so auch zur Reduktion des beschriebenen Effektes. Um solche Systeme testen zu können sind standardisierte Messmethoden nötig, die für Körperschall nicht existieren. Im Rahmen dieser Arbeit werden verschiedene Methoden untersucht, mit denen Körperschall in Ohrsimulatoren simulierbar gemacht werden kann. Zwei verschiedene Schallwandlerarten werden im Hinblick auf ihre Eignung hierfür untersucht. Hierzu werden akustische Messungen an einem vereinfachten Ohrkanalmodell gemacht. Aus den Ergebnissen werden Empfehlungen für die Erweiterung bestehender Ohrsimulatoren abgeleitet. Alle Interessierten sind herzlich eingeladen, eine Anmeldung ist nicht erforderlich. Allgemeine Informationen zum Kolloquium, sowie eine aktuelle Liste der Termine des Kommunikationstechnischen Kolloquiums finden Sie unter: https://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 14 Apr '21

14 Apr '21

Dear subscribers of the colloquium newsletter, we are pleased to announce the next date for our Communication Technology Colloquium: *Wednesday, April 21, 2021* *Speaker*: Irina Kharlamova *Time*: 11:00 a.m. *Location*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master Lectur*e: Primary-Ambient Aware Sound Field Translation Sound field translation is a technique that allows the sound field to be represented in a displaced coordinate system. This master's thesis presents a coherence-adaptive method of sound field translation based on space warping techniques. The proposed method moves mainly only the direct part of the signal and keeps the ambient part relatively unchanged. The system first identifies the direct and ambient components of the signal and then uses this data to build a filter-mask. For the first task, the method uses parametric decomposition of the sound field. A series of experiments have been conducted with single and multiple sources presented as directional noise or speech, also including reverberation. In experiments comparing other different translation methods, the proposed coherence-adaptive approach achieves excellent performance in terms of various instrumental metrics. All interested parties are cordially invited, registration is not required. General information about the colloquium as well as a current time scale of the Communication Technology Colloquium can be found at: https://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Kommunikationstechnisches Kolloquium am IKS
by Irina Ronkartz 30 Mar '21

30 Mar '21

Sehr geehrte Abonnenten des Kolloquium-Newsletters, gerne informieren wir Sie über den nächsten Termin unseres Kommunikationstechnischen Kolloquiums. *Dienstag, 6. April 2021* *Vortragender*: Florian Hilgemann *Zeit*: 10:00 Uhr *Ort*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master-Vortrag*: Numerische Optimierung rekursiver Filter für aktive akustische Equalisierung Aktive Störgeräuschunterdrückung (ANC) ist eine auf dem schnell wachsenden Markt für Hörsysteme von Kunden häufig nachgefragte Funktion und hat in der Vergangenheit zunehmend an Bedeutung gewonnen. Trotz jüngster Fortschritte im Bereich der digitalen Signalprozessoren (DSPs) werden ANC-Systeme zwangs hoher Anforderungen an Gehäusegröße und Stromverbrauch zusammen mit der Notwendigkeit hoher Abtastraten häufig mittels zeitinvarianten Digitalfiltern realisiert. In diesem Fall bieten Filter mit unendlicher Impulsantwort (IIR-Filter) eine attraktive Option für die Implementierung, da sie eine geringere Anzahl an Multiplizierern als Filter mit endlicher Impulsantwort (FIR-Filter) benötigen um eine Impulsantwort mit einer bestimmten Länge zu modellieren. Leider liefern herkömmliche Methoden für den Entwurf zeitinvarianter ANC-Filter entweder ein FIR-Filter oder erfordern andere Formen der Nachbearbeitung. Dies kann das Systemverhalten nachteilig beeinflussen und im Falle von Feedback ANC kann die Stabilität des Systems nicht ohne weiteres garantiert werden. Um die Notwendigkeit der Nachbearbeitung zu überwinden wird in dieser Arbeit ein alternativer Ansatz für den Entwurf von IIR-Filtern für Feedforward und Feedback ANC untersucht, welcher auf iterativen Optimierungsalgorithmen basiert. Dies führt unweigerlich zu nichtkonvexen Optimierungsproblemen, deren globales Optimum nicht ohne weiteres gefunden werden kann. Es wird jedoch gezeigt, dass der Ansatz trotz dieser Einschränkung eine praktikable Option darstellt. Eine wesentliche Neuerung des erarbeiteten Konzepts ist ein modularer Ansatz, der eine präzise Formulierung des Optimierungsziels unter Nebenbedingungen sowie eine flexible Anpassung an geänderte Anforderungen ermöglicht. Der Ansatz wird sowohl durch Simulationen als auch durch eine Echtzeitmessung mit einem Kunstkopf verifiziert. Weiterhin werden die Ergebnisse in Bezug zu einem theoretischen Optimum gesetzt, welches als Abschätzung für die mit einem zeitinvarianten Filter erzielbare Funktionsfähigkeit dient. Insgesamt deuten die Ergebnisse darauf hin, dass die resultierenden IIR-Filter gleich gut oder in vielen Fällen sogar besser als konventionelle Methoden abschneiden. Damit stellt der erarbeitete Ansatz einen wesentlichen Schritt in Richtung optimaler Funktionsfähigkeit dar. Alle Interessierten sich herzlich eingeladen, eine Anmeldung ist nicht erforderlich. Allgemeine Informationen zum Kolloquium sowie eine aktuelle Liste der Termine des Kommunikationstechnischen Kolloquiums finden Sie unter: http://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 14 Jan '21

14 Jan '21

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquium. *Wednesday, January 20, 2021* *Speaker:* Jonas Kuntzer *Time*: 11:00 a.m. *Location:* https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Master Lecture:* Speech Inpainting Using Recurrent Neural Networks Speech signals are often subject to transient noise signals that can appear anywhere in the frequency spectrum. When the noise over laps with frequencies of human speech, the removal of the noise inevitably leads to a deterioration in the quality of speech and a loss of information. Because speech is highly predictable in time, a speech inpainting neural network is presented which includes recurrent neural networks in the form of LSTMs whose strength lies in the prediction of sequential data. Furthermore, the SHAP algorithm is employed to gain an understanding of the impact of individual input features on the output and the network's dependence on individual time steps in the input sequences. The results demonstrate that LSTMs are well-suited to solve the problem of speech inpainting, outperforming other networks based on fully-connceted layers only. An increase in the PESQ and LSD score is observed compared to the corrupted signal. The increase is further enhanced when the sequences include not only past but also future data samples. Interpretation of the trained networks concludes that the prediction of output features is primarily based on their counterpart in the input features with the largest emphasis in the sequences being put on the current time step. All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of the dates of the Communication Technology Colloquium can be found at: http://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 23 Dec '20

23 Dec '20

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next dates of our Communication Technology Colloquium. Wednesday, January 6, 2021 Speaker: Raphael Brandis Time: 10:00 a.m. Location: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 Master Lecture: Personalized Occlusion Cancellation in Headphones and Hearing Aids To users of headphones, hearables, and hearing aids, the occlusion effect (OE) is still a largely unsolved problem that causes them to perceive the sound of their own voice differently. In surveys, users commonly describe this OE-affected own-voice sound as hollow, boomy, and unpleasant. Other body-conducted sounds are affected as well; examples include the noise originating from footsteps or chewing. A system that actively combats this effect has been in active development at the Institute of Communication Systems. This so-called Active Occlusion Cancellation (AOC) system is designed to cancel the average OE when applied to the average user’s occluded ear. Acoustic measurements as well as a listening test have shown it to be able to significantly reduce the OE and improve the users’ subjective experience. Unfortunately, both the OE and the acoustic characteristics of the occluded ear can vary significantly from user to user. That is why this thesis sets out to explore approaches to personalize the AOC system for individual users. First, an objective scalar metric for the OE is proposed. This metric is then used to automatically adjust two scalar gains already present in the AOC system. These gains allow for a limited degree of personalization and, up until now, had to be adjusted manually. Second, a technique to iteratively design a personalized feedback controller based on a user’s acoustic measurements is introduced. This feedback controller is a major part of the AOC system. For the limited amount of user measurements that are available, this new design technique manages to quickly and reliably converge onto a controller that meets both the performance and robustness requirements. The controller design process is fully automated and does not require manual intervention by a control engineer. Finally, both personalization approaches are evaluated in a listening test of limited scope and size due to the ongoing COVID-19 pandemic. and Wednesday, January 6, 2021 Speaker: Ulrik Deneken Time: 11:00 a.m. Location: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 Bachelor Lecture: Entwurf psychoakustisch optimierter signaladaptiver Übersprechkompensationsfilter Für die Wiedergabe binauraler Signale über Lautsprecher muss das verwendete binaurale Signal vorgefiltert werden, damit der Höreindruck erhalten bleibt. Das Problem bei der Wiedergabe durch Lautsprechern ist, dass die Kanäle des Signales nicht mehr klar getrennt sind. Signalteile für das eine Ohr erreichen auch das andere Ohr. Dieses Problem wird als Übersprechen bezeichnet. Das Übersprechkompensationsfilter löst dieses Problem, indem die Signale über den Kreuzpfad entfernt werden und die Signale über den Direktpfad möglichst verzerrungsfrei wiedergegeben werden. Mit Hilfe von psychoakustischer Maskierung soll in dieser Arbeit ein neuer Ansatz für die Entwicklung von Übersprechkompensationsfiltern gegeben werden. Das Signal des Kreuzpfades soll in diesem Ansatz nicht mehr vollständig verschwinden. Es würde ausreichen, wenn das Signal das Kreuzpfades unterhalb der Maskierungsschwelle des Signals des Direktpfades wäre. Hierzu wurden zwei Verfahren ausgearbeitet. Ein Verfahren beruft au fdem Ansatz einer konvexen Optimierung und wird im Frequenzbereich durchgeführt. Das andere Verfahren wird mittels nichtlinearer Nebenbedingungen im Zeitbereich gelöst. Es konnte gezeigt werden, dass die Filter hinsichtlich der Maskierung verbessert werden können. Dies ist aber mit einem großen Rechenaufwand verbunden und hängt stark von dem verwendeten Eingangssignal ab. Die nichtsignaladaptiven Methoden liefern ein passables Ergebnis, jedoch konnte gezeigt werden, dass eine Verbesserung möglich ist. All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of the dates of the Communication Technology Colloquium can be found at: http://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 01 Dec '20

01 Dec '20

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquium. *Tuesday, December 8, 2020* *Speaker*: Hendrik Stelzer *Time*: 10:00 a.m. *Location*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Bachelor Lecture*: Real-Time Use-Case Classification for Intelligent Control of Hearables A current goal in the development of headphones and hearables is that users can wear theam at any time. Especially with the integration of more and more features, specifically active noise cancellation (ANC) and transparency features, a method of recognizing different acoustic situations is necessary to enable intelligent control. In this thesis an approach for intelligent classification of the current wearing situation, or use case of headphones and hearing aids is investigated. In addition to the simple recognition of whether the earpiece is currently in use, the recognition of special cases such as different fittings and closing the speaker outlet is examined. The sensor signals used comprise one external and one internal microphone signal for each side of the head. Real-time capable features are extracted from the sensor signals and tested for their information content regarding a use case classification. Based on headphone simulations, a forward feature selection is conducted to find the set of features enabling the most robust classification regardless of any kinds of disturbane noise. The influence of both air conducted sound (ambient noise) and body conducted sound (e.g. talking or chewing) is considered. The mutual information is utilized to measure the quality of a feature. Five well-known real-time capable classification methods are then applied using the determined features and compared: the Fisher discriminant, the least squares discriminant, logistic regression, decision trees and Gaussian mixture models. Finally, the applicability of the developed principles is verified by an implementation on a real-time system (dSPACE ds1005) All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of the dates of the Communication Technology Colloquium can be found at: http://www.iks.rwth-aachen.de/aktuelles/kolloquium/ -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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Communication Technology Colloquium at IKS
by Irina Ronkartz 26 Nov '20

26 Nov '20

Dear subscribers of the colloquium newsletter, we are happy to inform you about the next date of our Communication Technology Colloquium. *Thursday, December 3, 2020* *Speaker*: Timothé Scheich *Time*: 11:00 a.m. *L**ocation*: https://rwth.zoom.us/j/97904157921?pwd=SWpsbDl0MWhrWjY1ZkZaeFRoYmErZz09 Meeting-ID: 979 0415 7921 Passwort: 481650 *Bachelor Lecture*: Methods for the Assessment of Headphones with Active Noise Cancellation Today, Active Noise Cancelling (ANC) headphones are a product daily used by most people. How goog the headphones sound and how well their ANC is working with respect to human perception, is still an open research topic. Only few researchers have been studying the matter and provided working measurement models. In this thesis, we first lay the groundwork for a comprehensive understanding of already existing ANC headphones assessment methods through an extensive research of related work. Therewith, this thesis also motivates the importance of considering psychoacoustic as an assessment tool by presenting several metrics describing pleasantnes and annoyance of a sound. Furthermore, two measurement series are conducted to gather ANC headphone performance measurement data using several background noises. The measurement set-up is explained, and the applied noise databases are presented. Later on, we propose an assessment model using some of the described metrics. Finally, we are able to highlight, by comparing the same type of on-ear headphones, the importance of psychoacoustical parameters that may allow differentiation of similarly performing objects. We conclude by explaining the results and propose a subjective test to corroborate our findings. All interested parties are cordially invited, registration is not required. General information on the colloquium, as well as a current list of the dates of the Communication Technology Colloquium can be found at: http://www.iks.rwth-aachen.de/aktuelles/kolloquium -- Irina Ronkartz Institute of Communication Systems (IKS) RWTH Aachen University Muffeter Weg 3a, 52074 Aachen, Germany +49 241 80 26958 (phone) ronkartz(a)iks.rwth-aachen.de http://www.iks.rwth-aachen.de/

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