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TU Berlin

Inhalt des Dokuments

Rafael Zequeira Jiménez


Research Topics

  • Speech Quality Assessment in Crowdsourcing  


Research Group

Next Generation Crowdsourcing



Rafael Zequeira Jiménez received a degree as Telecommunication Engineer (equivalent to Master of Science) from the University of Granada, Spain in 2014.

From 2013 to 2014 he studied at Technische Universität Berlin within the Erasmus program. At this time, he worked on his Master Thesis entitled: “Secure multi protocol system based on a Resource Model for the IoT and M2M services”. In December 2013, Rafael joined the SNET department of the Deutsche Telekom Innovation Laboratories (T-Labs), where he worked during 10 months as a student research assistant in the TRESOR project. In which he focused on designing and implementing REST APIs to communicate different components.

In June 2015 Rafael joined the Quality and Usability Lab department lead by Prof. Dr.-Ing. Sebastian Möller, to work as Research Assistant in the “Next Generation Crowdsourcing” group, specifically in the Crowdee project. Since 2016, he works towards his PhD in the topic: “Analysis of Crowdsourcing Micro-Tasks for Speech Quality Assessment”.




Twitter: @zequeiraj





Quality and Usability Lab
TU Berlin
Ernst-Reuter-Platz 7
D-10587 Berlin, Germany

Tel:  +4930835358336​


Effect of Number of Stimuli on Users Perception of Different Speech Degradations. A Crowdsourcing Case Study
Zitatschlüssel zequeirajimenez2018d
Autor Zequeira Jiménez, Rafael and Mittag, Gabriel and Möller, Sebastian
Buchtitel Proceedings of IEEE International Symposium on Multimedia (ISM)
Seiten 175–179
Jahr 2018
ISBN 978-1-5386-6857-3
DOI 10.1109/ISM.2018.00-16
Adresse Piscataway, NJ
Monat dec
Notiz electronic
Verlag IEEE
Serie ISM
Wie herausgegeben Fullpaper
Zusammenfassung Crowdsourcing (CS) has established as a powerful tool to collect human input for data acquisition and labeling. However, it remains the question about the validity of the data collected in a CS platform. Sometimes, the users work carelessly or they try to tweak the system to maximize their profits. This paper reports on whether the number of speech stimuli presented to the listeners has an impact on the user perception of certain degradation conditions applied to the speech signal. To this end, a crowdsourcing study has been conducted with 209 listeners that were divided in three non-overlapping user groups, each of which was presented with tasks containing a different number of stimuli: 10, 20, or 40. Listeners were asked to rate speech stimuli with respect to their overall quality and the ratings were collected on a 5-point scale in accordance with ITU-T Rec. P.800. Workers assessed the speech stimuli of the database 501 from ITU-T Rec. P.863. Additionally, the influence of certain speech signal characteristics, such as interruptions and bandwidth, on the quality perception of the workers was investigated.
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