Browsing by Subject "Reverberation"

Now showing 1 - 4 of 4

Open Access
Acoustical design and noise control in metro stations: Case studies of the Ankara metro system
(2007) Sü, Z.; Çalíşkan, M.
The aim of this research is to demonstrate the importance of initial strategies in acoustical design of underground metro stations. The paper searches for practical design solutions by evaluating different materials for providing optimum acoustical conditions in such spaces. Acoustical designs of three metro stations on a new expansion line in Ankara including Sogutozu, Bilkent and ODTU metro stations are presented through computer simulation. Predictions of room acoustical parameters are presented for both platform and ticket office floors in terms of parameters like reverberation time (RT), speech transmission index (STI) and A-weighted sound level (SPL) distribution within spaces. Simulated reverberation times are evaluated in view of legislative requirements. The study confirms the importance of using sound absorbing materials on the ceiling and sidewalls together. The nonwoven material, used behind perforated metal suspended ceilings, has proved effective in reverberation control.
Open Access
Assessment of reverberance perception and preferential acoustical conditions in educational atriums
(2022-07) Naeemaee, Rozhin
Atriums, with their large spans and superior voids, in modern life have changed their patterns of use from being only circulation zones to multi-functional gathering spaces. One solution to the challenge of transforming atriums to function as multifunctional spaces is optimizing the reverberation time. However, the optimum criteria of reverberation time for atriums have not yet well been set. This causes unnecessary intent of acoustical material applications within contemporary atriums. This study aims to provide a ground for such discussion on the optimum criteria, which can in the future lead to changes in standards and codes. With an aim of defining a proper range for reverberation per function and volume of the space, this research investigates the perception and preference of reverberation metrics (T30, EDT) within the context of educational atriums. The methodology starts with field tests and field surveys within four atriums of different departments at Bilkent University. Acoustical models of the atriums are tuned according to the field tests. Next, interior surface materials are modified for obtaining different sound energy decay rates and auralizations are applied to be used in subjective testing to seek preferential listening conditions. Produced audio clips by auralizations reflect different reverberation settings by the systemically increased amount of absorption, which is grouped for different intervals. An online listening test and questionnaire are held over a sample group of 67 students. Based on the analysis, the audio clips from groups G2 (1.00 s
Open Access
A comparison study on sound defects of Bilkent Amphitheatre in terms of intelligibility of the speech
(2007) Yilmazer, S.
The 4000 seated multi-purpose hall Bilkent Amphitheater is a semi-closed amphitheater with a large volume of 90,000 m3.At the beginning, the amphitheater was designed only for open-air performances. Afterwards it was decided to be roofed with a tensile membrane in order to protect the spectators against atmospheric effects. However, the covered amphitheater was turned into a very resounding and a problematic place with a reverberation time even more than 6 s. when the hall is unoccupied. After that time, some acoustical interventions were implemented, but these have not been sufficient in decreasing the number of problematic areas of echoes and dead spots. In 2000, Akukon Oy Consulting Engineers, Finland, carried out the real-size measurements when the hall was unoccupied, in order to find out the values of different acoustical parameters. In 2004, the computer simulation of the hall for the unoccupied condition was made [2]. In order to test speech intelligibility in the hall, besides the computer simulation and real size measurements, in 2006, articulation testing (AI) was made by using normal hearing listeners in the hall. In this paper, comparison between the measurements and the experimental studies are presented. Results confirm that excessive values of reverberation time cause too much reverberant and liveliness throughout the hall, besides the lack of warmth subjectively. Clarity is undermined by excessive reverberate and the sound becomes blurred. Sound energy are not satisfactory in reflecting the sound sufficiently through the hall and the direct sound becomes insufficient at some locations as back and mid sides.
Open Access
Perceived auditory environment in historic spaces of anatolian culture : a case study on Hacı Bayram mosque
(International Institute of Acoustics and Vibrations, 2016) Acun V.; Yilmazer, Semiha; Taherzadeh, P.
This article reports the initial finds of a research that is concerned with the perceived auditory environment within an historical mosque and its surroundings. Haci Bayram Mosque and its surrounding area of Hamamönü has been selected as the research site due to being the historical center of Ankara. Although there are studies concerned with the acoustical characteristics of mosques, there isn't enough research focusing on users' expectation and interpretation of the perceived auditory environment within a mosque. This study adopts the user focused of Grounded Theory to capture individuals' auditory sensation and interpretation of the perceived auditory environment within a historical mosque and its surroundings. In depth interviews are held with the congregation of the mosque and with the individuals sitting around the surrounding area. Based on their subjective responses, a theoretical framework is generated to gain an insight on the factors that affect individuals understanding and expectation from mosques. Acoustical characteristics of the mosque are analyzed by computer simulation and in-situ measurements of sound pressure levels. Objective room-acoustic indicators consist of reverberation time (RT) and speech transmission index (STI). The conceptual framework generated through Grounded Theory shows how perceived auditory environment may influence individuals' response to the physical environment of the mosque by showing the associations between the soundscape elements, spatial function and sense of place.