From sport to science: the acoustics of a pool transformed into an au- ditorium Umberto Berardi 1 Department of Architectural Science - Ryerson University 350 Victoria St. Toronto, Ontario M5B 2K3 – Canada Antonella Bevilacqua 2 Department of Industrial Engineering, University of Parma Area delle Scienze, Parma, 43126, Italy Nicola Chiacchio 3 University of Campania Luigi Vanvitelli Gino Iannace 4 University of Campania Campania Luigi Vanvitelli Amelia Trematerra 5 University of Campania Campania Luigi Vanvitelli

ABSTRACT A dismissed public building has been donated to the University of Foggia, Italy, due to the demand of facilities that the different departments requested for their academic meetings and events. This building, realized almost a hundred of years ago, was provided with a swimming pool on the ground floor, to be 25 m long and 3 m deep. The architects in charge to apply the change of use have designed the realization of an auditorium in place of the pool. The project consists of the installation of the audience seats on a 10% sloped stalls area, having a rectangular plan layout. The short dimension headwall, that is 3 m high, has been designed to allocate a screen for image and video projection. Before any change, a campaign of acoustic measurements has been undertaken in order to assess the existing conditions of the room, having a volume size of 4000 m3. The results from the first survey highlight that the main acoustic parameters were abundantly out of the optimal range defined for an

1 uberardi@ryerson.ca

2 antonella.bevilacqua@unipr.it

3 nicola.chiacchio1@studenti.unicampania.it

4 Gino.iannace@unicampania.it

5 amelia.trematerra@unicampania.it

worm 2022

auditorium. This paper deals with the acoustic design of an auditorium determined by some mitiga- tion solutions applied to lower the reverberation and increase the speech intelligibility in terms of Speech Transmission Index (STI). The addition of absorbing surface areas in an almost totally rever- berant room allowed the users to effectively make use of this facility. A second campaign of measure- ments carried out after the realization of the acoustic design have been analyzed and compared with the predictions.

1. INTRODUCTION

For the realization of the facilities selected to host the functions of the University of Foggia, a building realized during 1930s has been refurbished to be used as lecture halls. Part of this dismissed building is composed of a pool that has been transformed to an auditorium by installing the seats along a sloped floor. Despite of the good architectural design, the acoustics is lacking for the excessive reverberation that does not facilitate the speech comprehension, worsened especially with the operation of the am- plified audio system [1,2]. On this basis, some acoustic measures have been proposed and discussed in this paper in relation to the existing acoustic conditions of the auditorium, known before with the name of the Ex-Italian Youth’ Gym [3, 4].

2. ARCHITECTURAL ORGANIZATION AND DESIGN PORJECT

The shell of the auditorium consists of the existing pool, having dimensions of the plan equal to 13×26×11 m (L, W, H), having a total volume equal to 3870 m 3 . Figure 1 and 2 show respectively the plan layout and the longitudinal section.

worm 2022

Figure 1: Plan layout of the auditorium at the University of Foggia.

worm 2022

Figure 2: Longitudinal section of the auditorium at the University of Foggia. The existing room is characterized of 1500 m 2 of surface area, to be composed of all reflecting mate- rial. The architectural design project proposes the realization of the stalls grouped into two blocks and divided by a horizontal corridor that meets the criteria of the fire strategy in relation to escaping routes. The selection of the chairs falls to a medium thickness upholstery covered with a blue fabric. Behind the presidential desk, a screen of 6×5 m has been installed for the projection of students’ dissertations [5, 6]. The acoustic measures to lower the reverberation are composed of absorbing acoustic panels applied to the side walls of the basement level, specifically at the right and left sides of the presidential desk. Additional absorbing panels have been designed to be covering the windows, on the side and back- walls, to be always vertically hung, as shown in Figure 3 [7, 8]. The surface area of the ceiling has been treated with absorbing white cylinders, hung at regular dis- tance along the longitudinal axis.

Figure 3: Internal view of the auditorium at the University of Foggia.

3. ACOUSTIC MEASUREMENTS

Two sets of acoustic measurements have been carried out inside the auditorium, by using the fire- crackers as the impulsive sound source, provided with a good signal to noise ratio (S/N), and with a Brahma microphone as a receiver [9-12]. The sound source has been placed on the desk while the microphone has been moved across all the sitting area by following a regular grid. The acoustic meas- urements have been undertaken before and after the installation of the acoustic treatments, without any audience in both scenarios [13].

3.1 Results The results of the main acoustic parameters have been assessed in accordance with ISO 3382-1. Fig- ure 4 to 7 indicate the measured values of EDT, T 30 , C 50 and D 50 in the octave bands comprised between 125 Hz and 4 kHz [14].

worm 2022

Figure 4: Measured values of EDT.

Figure 4 indicates the EDT values measured before the acoustic treatment to be around 5.5 s at 250 Hz and not lower than 3 s in any octave. The values have been lowered to 2 s considered averaged across all the bandwidth, which is more suitable for conferences and discussions [15, 16].

EDT,s —* After Acoustic Treatment ~®- Before Acoustic Treatment 125° 250 © 500-1000 2000» 4000 Frequency, Hz

Figure 5: Measured values of T 30 .

730, s -@ After Acoustic Treatment ~@- Before Acoustic Treatment 125 250 += 500-1000 Frequency, Hz 2000 4000

Figure 5 shows the T 30 results, to be very similar to EDT. By the application of the acoustic measures the values dropped to 2.2 s at mid frequencies, with a variation of 0.5 s at low and higher octaves. To be noticed that the measured values shall be considered under unoccupied conditions of the room, therefore the values will be lowered when the occupancy will be in place [17].

worm 2022

Figure 6: Measured values of C 50 .

Figure 6 indicates the values of speech clarity index (C 50 ) to be below the lower range limit before any treatment. With the absorption panels on walls and ceiling, the values result within the optimal range (-2 dB to +2 dB). This outcome means that the acoustic response of the auditorium is suitable for speech understanding.

—& After AT —® Before AT 125 250 += 500-1000 Frequency, Hz 2000 ©4000

Figure 7: Measured values of D 50 .

Figure 7 shows the measured values of definition. In particular, before the application of the acoustic measures the values where between 0 and 0.2, very low for a good speech comprehension. After the

-@ After Acoustic Treatment —@- Before Acoustic Treatment 125 250 © 500-1000 Frequency, Hz 2000 4000

installation of the acoustic panels the results are around 0.4 at all octaves, with the exception of 125 Hz where the value is 0.2. While for the STI parameter it was before STI = 0.35, after than acoustic correction STI=0.6.

4. CONCLUSIONS

Overall, the acoustic design of the auditorium at the University of Foggia highlights a good acoustic response due to the application of the acoustic panels, designed to be uniformly distributed over the surface areas of walls and ceiling. This acoustic design allows the acoustic parameters to be closer the optimal range, by improving the speech understanding and word definition that otherwise was impacted by an excess of reverberation. Future research studies will be focusing onto the changes of the acoustic parameters with the presence of audience at different percentage of occupancy in order to evaluate a potential addition of absorbing material that fully meet the criteria of a room having such volume size. 6. REFERENCES

1. Barron, M. Auditorium Acoustics and Architectural Design, E&FN SPON, London, 1993 2. Iannace, G., Ciaburro, G., Trematerra, A., Foglia, C. Acoustic correction of a renaissance period

hall. Canadian Acoustics - Acoustique Canadienne 47(2) , 57–66 (2019). 3. Merli, F., Bevilacqua, A., Tronchin, L. The acoustic study of the palatine chapel inside the Reggia

of Caserta. In proc of Immersive and 3D Audio : From Architecture to Automotive, I3DA (2021) 4. Lombardi, I., Cicala, S., Iannace, G. Trematerra, A., The Acoustic Characteristics of the "Dives

in Misericordia" Church. In proc of 47th International Congress and Exposition on Noise Control Engineering - INTER-NOISE (2018). 5. Penman, K.A., Englund, J. S., Stanier, N., Reverberation and noise levels in sports areas”, Journal

of the Acoustical Society of America 62 , 1046–1048 (1977). 6. Iannace G. Sport Hall Acoustics. Noise & Vibration Worldwide 46(10), 22-29 (2015).

doi:10.1260/0957-4565.46.10.22 7. Russ, B. From Sports Arena to Sanctuary: Taming a Texas-sized reverberation time, Acoustics

Today 7 , 24–28 (2011). 8. Iannace, G., Berardi, U., De Rossi, F., Mazza, S., Trematerra, A., Ciaburro, G. Acoustic Enhance-

ment of a Modern Church. Buildings 9, 83 (2019). DOI: 10.3390/buildings9040083 9. Bošnjakovic, R., Tomic, D. Acoustical Treatment of Multipurpose Sport Halls. In Proc. of 3rd

Congress of the Alps Adria Acoustics Association , 27–28 September, Graz – Austria (2007). 10. Brezina, P. Measurement of intelligibility and clarity of the speech in romanesque churches. J.

of Cultural Heritage 16 (3) 386–390 (2015). DOI: 10.1016/j.culher.2014.06.010 11. Ciaburro, G., Iannace, G., Lombardi, I., Trematerra, A. Acoustic design of ancient buildings: The

odea of Pompeii and Posillipo. Buildings 10(12), 1-16 (2020). DOI: 10.3390/buildings10120224 12. Iannace, G., Berardi, U., Ciaburro, G., Trematerra, A. Egg cartons used as sound absorbing sys-

tems. Proceeding. of International Congress on Noise Control Engineering , INTER-NOISE 2020, (2020).

worm 2022

13. ISO 3382-1:2009. Acoustics – Measurement of the reverberation time of rooms with reference to

other acoustical parameters . 14. Tronchin, L. Variability of room acoustic parameters with thermo-hygrometric conditions. Ap-

plied Acoustics (2021), 177, 107933. 15. Merli, F., Tronchin, L. On the influence of thermo-hygrometric conditions in 3D acoustic meas-

urements. In proc. of Immersive and 3D Audio: From Architecture to Automotive , I3DA (2021). 16. Tronchin, L., Bevilacqua, A. Evaluation of acoustic similarities in two Italian churches honored

to S. Dominic. Applied Sciences 10(20), 1–16, 7043 (2020). 17. Beranek, L.L., Hidaka, T. Sound absorption in concert halls by seats, occupied and unoccupied,

and by the hall's interior surfaces. Journal of the Acoustical Society of America , 104, 3169–3177 (1998).

worm 2022