Browsing by Subject "Noise levels"

Now showing 1 - 4 of 4

Open Access
Dipole source reconstruction of brain signals by using particle swarm optimization
(IEEE, 2009) Alp, Yaşar Kemal; Arıkan, Orhan; Karakaş, S.
Resolving the sources of neural activity is of prime importance in the analysis of Event Related Potentials (ERP). These sources can be modeled as effective dipoles. Identifying the dipole parameters from the measured multichannel data is called the EEG inverse problem. In this work, we propose a new method for the solution of EEG inverse problem. Our method uses Particle Swarm Optimization (PSO) technique for optimally choosing the dipole parameters. Simulations on synthetic data sets show that our method well localizes the dipoles into their actual locations. In the real data sets, since the actual dipole parameters aren't known, the fit error between the measured data and the reconstructed data is minimized. It has been observed that our method reduces this error to the noise level by localizing only a few dipoles in the brain.
Open Access
An experimental study on speech interference in public leisure spaces
(Institute of Noise Control Engineering, 2010) Yilmazer, Semiha; Gezginer, Pelin Meriç
Physical comfort requirements of users in the non-acoustical spaces, leisure space, and usability of the space in long-term period should be taken into consideration in terms of sustainability of the space. The aim of this study is to investigate the speech interference of users' in an openplaned public leisure space. Bilkent Rollhouse was chosen as a leisure space because of its variance of activities in an open-plan like bowling, dart, billiards, play station and dining area. In this respect, a questionnaire was prepared to check the perception of sound of different user types in the area. The questionnaires were applied at the most crowded day of the week that is Friday and in between 18:00 to 21:00. The results of the survey were evaluated statistically. In addition to this, the equivalent continuous noise level, Leq, of the leisure space were taken in parallel to the questionnaire application to the users. Measuring of speech intelligibility via articulation index (AI) subjectively was the second phase of this study. Via application of the word list to the normal hearing users, the AI contours were prepared. Finally, objective and subjective measurements were analyzed in terms of speech interference during leisure activity in the space. As a leisure space, the relation between noise annoyance ratings and Leq did not show any significant difference in dart, billiards and play stations activities. However, in bowling activity and dining area, it was found that there is a significant relation between noise annoyance and Leq. This study reveals that users submit ambient noise of the space during leisure activity, they get in a common behaviour psychologically, they adjust their vocal noise that they create and finally these issues lead controlling of ambient noise by them. It means that users give up loudly speaking, they accept repeating or silence, focus on meal and they do not like getting in uncomfortable situation since their main activity is dining. For further study, the number of the samples in not only different leisure spaces, but also measurement points and sampling times should be increased to make clear hypothesis given above, since the study reveals completely different behaviour that is introduced in literature like cocktail party effect phenomenon.
Open Access
Relationships between measured levels and subjective ratings: A case study of the food-court area in CEPA shopping center, Ankara
(SAGE, 2012-03-01) Dökmeci, P. N.; Yilmazer, S.
Physical comfort requirements of users; such as, thermal, visual, and acoustic comfort, should be considered and studied in detail when planning and designing public spaces. However, there is not enough research on the relations between the acoustical parameters, and the acoustic comfort level of users in enclosed non-acoustic public spaces, which are directly connected with a central atrium. In such spaces, evaluation on auditory perception and noise annoyance should be performed in parallel with objective parametric measurements. The food-court area of CEPA Shopping Center, with a central atrium and a glass ceiling structure, in the capital city of Turkey, Ankara is chosen for the case. The aim of this study is to investigate the relationships between the users' subjective ratings of noise levels and the measured equivalent continuous sound pressure levels (Leq). In addition, the demographical differences and user profile variances, as well as the auditory perception classifications are investigated in this case space. The present acoustical indices are measured and then discussed by pointing out the architectural features of the case space, which are the central atrium, glass ceiling structure and the sound reflective material applications. The research methods include, noise measurements to obtain Leq and questionnaires to assess the subjective ratings and auditory perception of the users. This study mainly concentrates on the food-court space, which is within CEPA Shopping Center and displays the significant results regarding this space. These results show that Leq values vary by different day types (weekdays and weekends) and time of day, and the subjective ratings correlate well with these Leq variances. The most dominant sound perceived by the users was found to be the hum of voices. One other significant result implies that, subjective ratings of noise level becomes significant above 67 dBA and shows a sudden increase in the ratings. Furthermore, the time spent in the food-court area correlated significantly with noise annoyance ratings.
Open Access
Systematic evaluation of face detection algorithms on news videos
(IEEE, 2007) Acar, Can; Atlas, Arda; Çevik, Koray; Ölmez İsa; Ünlü, Mustafa; Özkan, Derya; Duygulu, Pınar
People are the most important subjects in news videos and for proper retrieval of people images; face detection is a very crucial step. However, face detection and recognition in news videos is a very challenging task due to the huge irregularities and high noise level in the data. In addition to that, with different face detection algorithms, the number and the type of the faces may differ. In this study, in order to get the best performance from existing methods, systematic evaluation of these methods is performed. In the experiments, news videos from TRECVID 2006 data set are used and for evaluation four different face detection methods are chosen.