Abstract
Good speech intelligibility in university classrooms is crucial to the learning process, ensuring that students can clearly hear all conversations taking place in the classroom. While it is well known that speech intelligibility depends on the geometrical characteristics of a space and the properties of its surfaces, other factors need also to be considered. Among the most important are: the heating, ventilation, and air conditioning (HVAC) systems used in classrooms. Fan noise from HVAC systems increases the background noise level (BNL), negatively affecting speech intelligibility. In addition, the movement of air caused by these systems alters room acoustic variables. Although this dynamic situation is often overlooked in the early design stages, HVAC systems are often active during lectures and influence acoustics variables, especially the speech transmission index (STI). In this study, the impact of HVAC systems on the STI was measured in five different unoccupied classrooms in the Rafet Kayıș Faculty of Engineering at Alanya Alaaddin Keykubat University. The results were evaluated according to relevant standards. The results of these evaluations offer insights for researchers, architects, and engineers working in the field of acoustics.Keywords:
speech intelligibility, speech transmission index (STI), room acoustic variables, room impulse response (RIR), acoustic performanceReferences
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6. Cushing I.R., Li F.F., Cox T.J., Worrall K., Jackson T. (2011), Vocal effort levels in anechoic conditions, Applied Acoustics, 72(9): 695–701, https://doi.org/10.1016/j.apacoust.2011.02.011.
7. Di Loreto S., Cantarini M., Squartini S., Lori V., Serpilli F., Di Perna C. (2023), Assessment of speech intelligibility in scholar classrooms by measurements and prediction methods, Building Acoustics, 30(2): 165–202, https://doi.org/10.1177/1351010X231158190.
8. Elliott T.M., Theunissen F.E. (2009), The modulation transfer function for speech intelligibility, PLoS Computational Biology, 5(3): e1000302, https://doi.org/10.1371/journal.pcbi.1000302.
9. Engel M., Herrmann J., Zannin P. (2020), Assessment of the sound quality of classrooms through speech transmission index (STI), sound definition (D50) and reverberation time (RT), Forum Acusticum.
10. Guidorzi P.A., Barbaresi L.U., D’Orazio D.A., Garai M.A. (2015), Impulse responses measured with MLS or Swept-Sine Signals applied to architectural acoustics: An in-depth analysis of the two methods and some case studies of measurements inside theaters, Energy Procedia, 78: 1611–1616, https://doi.org/10.1016/j.egypro.2015.11.236.
11. Houtgast T., Steeneken H. J. (1985), A review of the MTF concept in room acoustics and its use for estimating speech intelligibility in auditoria, The Journal of the Acoustical Society of America, 77(3): 1069–1077, https://doi.org/10.1121/1.392224.
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14. International Organization for Standardization (2009), Acoustics – Measurement of room acoustic parameters – Part 1: Performance spaces (ISO Standard No. 3382-1:2009), https://www.iso.org/standard/40979.html. (access: 05.09.2024).
15. International Organization for Standardization (2014), Acoustics – Field measurement of sound insulation in buildings and of building elements – Part 1: Airborne sound insulation (ISO Standard No. 16283-1:2014), https://www.iso.org/standard/55997.html. (access: 05.09.2024).
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22. Mejdi A., Gardner B., Musser C. (2019), Prediction of the speech transmission quality in the presence of background noise using the ray tracing technique, [in:] 26th International Congress on Sound and Vibration (ICSV), https://www.academia.edu/64361351/Prediction. of the Speech Transmission Quality in the Presence of Background Noise Using the Ray Tracing Technique (access: 15.11.2024).
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29. Razali A.W., Din N.B.C., Yahya M.N., Sulaiman R. (2024), Conceptual framework of acoustic comfort design enablers for a classroom: A systematic review, Journal of Building Engineering, 95: 110160, https://doi.org/10.1016/j.jobe.2024.110160.
30. Rossing T.D. [Ed.] (2014), Springer Handbook of Acoustics, 2nd ed., Springer, Germany.
31. Yang D., Mak C.M. (2018), An investigation of speech intelligibility for second language students in classrooms, Applied Acoustics, 134: 54–59, https://doi.org/10.1016/j.apacoust.2018.01.003.
32. Zhu P., Tao W., Mo F., Lu X., Zhang H. (2024), Experimental comparisons of speech transmission index prediction methods, Applied Acoustics, 220: 109985, https://doi.org/10.1016/j.apacoust.2024.109985.
