Browsing by Subject "Reverberation time"

Now showing 1 - 6 of 6

Embargo
Acoustical assessment of music halls with variable systems through objective and subjective methods: the case of Bilkent Music Hall
(2024-07) Altun, Aslı
In concert halls, the need for variable acoustics elements arises from the diverse demands posed by different types of musical performances. Previous research suggests that incorporating passive variable acoustic solutions can effectively adapt acoustical conditions to suit various musical performance needs. This research explores the challenges and potentials associated with passive variable acoustic techniques in symphonic music venues, with a focus on Bilkent Music Hall in Ankara, Türkiye. This venue serves as the main performance space for the Bilkent Symphony Orchestra (BSO) and is one of the earliest examples of variable acoustic systems. Over this case, the impact of the existing variable acoustic system for diverse musical performances such as chamber music, orchestral music, orchestral music with choir and vocal accompaniment, solo recitals, and occasional speech-oriented activities is investigated. The methodology begins with acoustical field measurements to evaluate the existing variable acoustic system at Bilkent Music Hall, which consists of operable wooden doors with fabric backing. This analysis highlights the need to investigate the contribution of interior finishing materials to excessive sound absorption at low frequencies, as one major problem of the hall. As a second step of the methodology, subjective data is collected through questionnaire and online surveys that are administered to BSO members and Bilkent Music Conservatory faculty and students. The analysis offers insights into the musicians’ acoustical experiences and acoustical preferences in relation to the venue. Later, the findings are compared with precedent cases worldwide. The final step of the study is acoustical simulations that is applied first to assess the occupied state of the hall then to evaluate the proposed design intervention for improving the acoustical comfort within the hall for different music performances.
Open Access
The acoustical characteristics of the Kocatepe Mosque in Ankara, Turkey
(Taylor & Francis, 2008) Sü, Z.; Yilmazer, S.
This research investigates the acoustical characteristics of mosques of the classical Ottoman period and the contemporary period. Kocatepe Mosque, the major mosque in Ankara, Turkey, as a case from the contemporary era is a unique combination of 16th century Ottoman aesthetics and 20th century technology. Although previous and recent mosques have been inspired by this combination, the use of a reinforced concrete dome without cavity resonators could cause long reverberation times especially in low frequencies. The purpose of this study was to investigate this condition by studying Kocatepe Mosque. The acoustical characteristics of the mosque were analyzed by computer simulation. Objective room-acoustic indicators including reverberation time (RT), early decay time (EDT), clarity (C80), definition (D50), lateral fraction (LF), speech transmission index (STI) and strength (G) are presented. The results show that the acoustical quality of Kocatepe Mosque is not optimal when it is empty, and closest to optimal conditions when fully occupied. The new techniques to overcome excessive low frequency attenuation caused by huge concrete shells of today's mosques are discussed in conclusion.
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
Developing wideband acoustic absorbers in interior spaces: modelling, measurements and applications
(2024-01) Fasllija, Ela
This study aims to develop wideband acoustic absorbers in interior spaces for speech purposes, through the use of Micro-Perforated Panels (MPPs) arranged in different configurations. The research has involved theoretical modelling, measurements, and applications in interior spaces. The initial phase focused on modelling various MPP arrangements and predicting their sound absorption coefficients using the Electric Equivalent Circuit Model (ECM) under normal and oblique incidence conditions. Small samples with different geometric parameters were then manufactured and tested for their absorption coefficients at the Turkish Standards Institute, following the impedance tube method (ISO 10534-2:1998). The preliminary results showed a good agreement with the numerical predictions. Furthermore, the random incidence absorption coefficient of a parallel arranged MPP structure was measured in a Small-Scale Reverberation Room (SSRR) at Bilkent University to evaluate the proposed structure in a diffuse field. The results obtained by using ISO 354:2003 showed lower values than the predicted ones by a range of 0.1- 0.3. However, there was a better alignment between the ECM predictions and experimental results for 30-degree oblique incidence. Regarding interior applications, a classroom with poor acoustics was treated in ODEON 16 using the proposed material in the form of a wall panel. The effect of the developed material on objective room acoustics parameters was examined, revealing improvements in the Reverberation Time and Speech Intelligibility Index values. Lastly, the Turkish versions of Perceived Affective Qualities outlined in the ISO/TS 12913-2:2018 standard were developed to assess the subjective perception of the material following the soundscape approach.
Open Access
Effects of perceived singing effort on classical singers’ reverberation time preferences towards music practice rooms
(Elsevier, 2018) Sinal, Özgün; Yılmazer, Semiha
The purpose of this study is to investigate the effect of perceived singing effort on classical singers’ reverberation time preferences in individual music practice rooms. The method has combined objective measurements (RT) and perceptual responses of participants. The participant group [N = 30] has consisted of five different backgrounds in vocal studies; early music education (EME) students, skilled amateurs, undergraduate singing students, graduate singing students, and professionals. Classical singers has been asked to sing with as high and as low as they could with melisma singing style (in opera singing technique) in three different room settings which had following reverberation times; around 0.6 s, 0.8 s, and 1.0 s. These were the values, which acoustical standards for music schools recommended. The participants have also been asked to sing with three different singing volumes in each room setting. The findings have been analysed statistically. The results showed that classical singers have preferred the room setting with 0.8 s reverberation time considering their overall experience in these room settings. Classical singers’ perceived singing effort had a statistically significant relationship with preferred room setting. Furthermore, it has been found that there is a relationship between preference and background in vocal studies.
Open Access
Investigating the potential of transparent parallel-arranged micro-perforated panels (MPPs) as sound absorbers in classrooms
(MDPI AG, 2023-01-13) Fasllija, Ela; Yılmazer, Semiha
Acoustic deficiencies due to lack of absorption in indoor spaces may sometime render significant buildings unfit for their purpose, especially the ones used as speech auditoria. This study investigates the potential of designing wideband acoustic absorbers composed of parallel arranged micro-perforated panels (MPPs), known as efficient absorbers that do not need any other fibrous/porous material to have a high absorptive performance. It aims to integrate architectural trends such as transparency and the use of raw materials with acoustical constraints to ensure optimal indoor acoustic conditions. It proposes a structure composed of four parallel-arranged MPPs, which have been theoretically modelled using the electrical Equivalent Circuit Model (ECM) and implemented on an acrylic prototype using recent techniques such as CNC machining tools. The resulting samples are experimentally analysed for their absorption efficiency through the ISO-10534-2 method in an impedance tube. The results show that the prediction model and the experimental data are in good agreement. Afterward, the investigation focuses on applying the most absorptive MPP structure in a classroom without acoustic treatment through numerical simulations in ODEON 16 Acoustics Software. When the proposed material is installed as a wall panel, the results show an improvement toward optimum values in Reverberation Time (RT30) and Speech Transmission Index (STI).