Research

Al-bayyar, Z., Kitapci, K. (2021). An acoustic sense of place evaluation framework based on the room acoustic indicators. e-Forum Acusticum 2020, Lyon, France.

Conference paper

This study aims to present a room acoustics evaluation framework, which facilitates the influence of Sense of Place and its constructs: Place Attachment, Place Identity, and Place dependence. Sense of place is argued to be an ideal integration of the environmental context with users’ understanding and experience of the built environment. This holistic experience of places is inescapable since the quality of human senses is always reflected in the spaces. As the place is commonly defined as the combination of physical and cultural elements, it is hypothesized that room acoustics affects the sense of size, volume, and spatial awareness. Furthermore, sense of place leads to certain attitudes and behaviors from users, those are reflected towards developing the experienced place, and hence affecting the overall quality of the built environment. This study investigates the objective evaluation methods of the sense of place constructs and room acoustic parameters to develop a holistic acoustical evaluation model towards enhancing the multisensory experience of the built environment.

Kitapci, K. (2019). Room acoustics education in interior architecture programs: A course structure proposal. Paper presented at the INTER-NOISE 2019 – 48th International Congress and Exposition on Noise Control Engineering, Madrid, Spain.

Conference paper

Soundscape research alters the notion of room acoustics from a physical phenomenon to a new multidisciplinary approach that concerns human perception of the acoustic environment, in addition to the physical calculations and measurements. Many interior architecture programs include courses that specifically focus on room acoustics. Although a brief introduction to the technical aspects of room acoustics is considered mandatory, the current course structure does not deliver sufficient information on the human perception of the acoustic environment. Therefore, the aim of the study is to reconsider the structure of room acoustic courses and present a brand-new room acoustics course structure proposal for the interior architecture programs. The study consists of two main phases. In the first phase, a database of all courses that include various topics on room acoustics is prepared through examination of the course descriptions of all undergraduate and graduate interior architecture programs in Turkey. In the second phase, the revisions to the current state of the room acoustics course structures are advised through an in-depth systematic literature review on the research area of soundscapes. Preliminary results and the initial course structure model will be presented at the conference.

Kitapci, K., & Galbrun, L. (2019). Perceptual analysis of the speech intelligibility and soundscape of multilingual environments. Applied Acoustics, 151.

Original research paper

This paper examines the perceived speech intelligibility of English, Polish, Arabic, and Mandarin and, more generally, the soundscape associated to multilingual environments. Listening tests were used to evaluate three acoustic environments (an airport, a hospital, and a café) under three room acoustic conditions defined by a different speech transmission index (STI) (STI=0.4, 0.5 and 0.6). In the tests, participants rated eleven semantic attributes representative of speech perception and the overall soundscape (speech intelligibility, speech level, speech pleasantness, noisiness, annoyance, relaxation, comfort, environment pleasantness, eventfulness, excitement, and familiarity). Results obtained indicate that inter-language comparisons based on perceived speech intelligibility are different from those obtained from objective speech intelligibility tests. Noticeably, English participants were found to be most sensitive to changes in room acoustic conditions and to meaningful and distractive noise sources, whilst Arab participants were least sensitive to changes in room acoustic conditions and more tolerant to noise. Perceived speech intelligibility correlated significantly with non-acoustical factors (speech pleasantness, comfort and environment pleasantness), and ‘emotional factors’ (annoyance, relaxation, comfort and environment pleasantness) explained a large portion of the variance in soundscape assessment. Results also showed that language affected the perceived speech intelligibility marginally (p = 0.051) and noisiness significantly (p = 0.047), the latter being the best indicator of cultural variations amongst the attributes tested. Overall, the study shows that designing for speech intelligibility cannot be solely based on room acoustic parameters, especially in the case of multi-lingual environments.

Galbrun, L., & Kitapci, K. (2016). Speech intelligibility of english, polish, arabic and mandarin under different room acoustic conditions.

Conference paper

This paper examines the impact of room acoustic conditions on the speech intelligibility of four languages (English, Polish, Arabic and Mandarin). Listening test scores (diagnostic rhyme tests, phonemically balanced word tests and phonemically balanced sentence tests) of the four languages were compared under four room acoustic conditions defined by their speech transmission index (STI = 0.2, 0.4, 0.6 and 0.8). The results obtained indicated that there was a statistically significant difference between the word intelligibility scores of languages under all room acoustic conditions, apart from the STI = 0.8 condition. English was the most intelligible language under all conditions, and differences with other languages were larger when conditions were poor (maximum difference of 29% at STI = 0.2, 33% at STI = 0.4 and 14% at STI = 0.6). Results also showed that Arabic and Polish were particularly sensitive to background noise, and that Mandarin was significantly more intelligible than those languages at STI = 0.4. Consonant-to-vowel ratios and languages’ distinctive features and acoustical properties explained some of the scores obtained. Sentence intelligibility scores confirmed variations between languages, but these variations were statistically significant only at the STI = 0.4 condition (sentence tests being less sensitive to very good and very poor room acoustic conditions). Overall, the results indicate that large variations between the speech intelligibility of different languages can occur, especially for spaces that are expected to be challenging in terms of room acoustic conditions. Recommendations solely based on room acoustic parameters (e.g. STI) might then prove to be insufficient for designing a multilingual environment.

Galbrun, L., & Kitapci, K. (2014). Accuracy of speech transmission index predictions based on the reverberation time and signal-to-noise ratio. Applied Acoustics, 81, 1-14.

Original research paper

This paper examines the accuracy of the speech transmission index (STI) calculated from the reverberation time (T) and signal-to-noise ratio (LSN) of enclosed spaces. Differences between measured and predicted STIs have been analysed in two rooms (reverberant vs. absorbent), for a wide range of absorption conditions and signal-to-noise ratios (sixteen tests). The STI was measured using maximum length sequence analysis and predictions were calculated using either measured or predicted values of T and LSN, the latter assuming diffuse sound field conditions. The results obtained for all the conditions tested showed that STI predictions based on T and LSN tend to underestimate the STI, with differences between measured and predicted STIs always lower than 0.1 (on a 0.0–1.0 scale), and on average lower than 0.06. According to previous research, these differences are noticeable and therefore non-negligible, as 0.03 is the just noticeable difference in STI. The use of either measured or predicted values of T and LSN provided similar STI predictions (i.e. non-noticeable changes), with differences between predictions that are on average lower than 0.03 for the absorbent room, and lower than 0.01 for the reverberant room.

Kitapci, K., Yılmazar, S. (2018). Acoustics and speech privacy in open-plan offices: a case study on computer-based task performance. GRID – Mimarlık, Planlama ve Tasarım Dergisi Volume, 1, 1-23.

Original research paper

The aim of this study is to find out the effects of speech and speech intelligibility on computer-based task performance in open-plan offices. The research was conducted in a real open-plan office environment to include the open-office experience of subjects to the analysis. STM Bilkent Office was selected as the case, and 40 available open-office occupants were participated to the study. The experiment consists of two main phases. In the first phase, acoustical simulation of the site was done, to derive distribution graphs for speech related room acoustics parameters. In the second phase, occupants’ computerbased task performances were tested under three different sound environments, which are continuous noise, speech and masked speech. According to statistical analysis of the performance test, and the acoustical properties of the case STM, suggestions for renovation were discussed. It was found that effects of intelligible speech on occupants’ task performance are only psychological, because it is significant that there is no difference between results of performance test. However, all of the occupants respond to the questionnaires that speech sound environment was the most distracting one. Proposal for renovation was given to minimize the effects of intelligible speech on occupants for preventing the long-term effects on occupants’ health. 

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