Design of virtual binaural manikins and auditorium acoustic modelling Eusébio Z. E. Conceição 1 Faculdade de Ciências e Tecnologia - Universidade do Algarve Campus de Gambelas, 8005-139 Faro, Portugal Mª Inês L. Conceição 2 Instituto Superior Técnico Av. Rovisco Pais, 1049-001 Lisboa, Portugal Mª Manuela J. R. Lúcio 3 Universidade do Algarve Campus de Gambelas, 8005-139 Faro, Portugal João Gomes 4 CINTAL Campus de Gambelas, 8005-139 Faro, Portugal Hazim Awbi 5 University of Reading Campus de Gambelas, 8005-139 Faro, Portugal

ABSTRACT In this work a numerical model is applied in the development of the design of Virtual Binaural Manikin and Auditorium Acoustic Modelling. The binaural acoustic manikin is based in Human Thermal Modelling, using the Human Body Geometry Modelling, and the Sound Propagation Modeling numerical models. The Auditorium Acoustic Modelling considers the Auditorium Thermal Modelling, using auditorium geometry, and the Sound Propagation Modeling numerical models. The manikin and the auditorium geometry are developing with the Computed Aid Design, CAD, methodology. The Sound Propagation Modeling of the Virtual Binaural Manikin calculates the reverberation time and the Sound Propagation Modeling of the Auditorium Acoustic Modelling calculate the direct and indirect sound using the acoustic path.

In this study an auditorium with a maximum occupation level of 168 manikins is developed. One manikin of the stage and three virtual binaural manikins in the audience was selected to be evaluate

1 econcei@ualg.pt 2 ines.conceicao@tecnico.ulisboa.pt 3 maria.manuela.lucio@gmail.com 4 jgomes@ualg.pt 5 mail2@example.com

the acoustical path and reverberation time. The acoustic level, in the left and right ears, that the virtual manikins are subjected are evaluated.

Keywords: Auditorium acoustic system, virtual binaural manikin, reverberation time

1. INTRODUCTION

In this work the Binaural Acoustic Manikin and Auditorium Acoustic Modelling are presented and applied. The Binaural Acoustic Manikin is based in the Human Thermal Modelling (Human Body Geometry Modelling) and the Sound Propagation Modeling numerical models. The Auditorium Acoustic Modelling considers the Auditorium Thermal Modelling (auditorium geometry) and the Sound Propagation Modeling numerical models. The manikin and the auditorium geometry are developing with the of the CAD methodology.

The Human Thermal Modelling calculate the:

 distribution of body tissue temperature, the clothing temperature, the arterial and venous blood

temperature, the skin water vapour and the clothing water vapour. This numerical software calculate the thermal comfort level (see Fanger [1], ISO 7730 [2] and ASHRAE 55 [3]), that each occupant are subjected and indoor air quality (see Conceição et al. [4]). Application of this numerical model can be see in Conceição and Lúcio [5], using experimental and numerical values, Conceição et al. [6], using a coupling methodology with the CFD, and Conceição et al. [7], using experimental data as input;  human body three-dimensional geometry. The manikin geometry is generated through

geometric equations, based in the weight and height. The manikin geometry, considers 1 sphere elements and 24 cylindrical elements, namely the head, neck, chest, abdomen, right shoulder, right arm, right hand, left shoulder, left arm, left hand, right thigh, right leg, right foot, left thigh, left leg and left foot. The Sound Propagation Modeling of the Binaural Acoustic Manikin calculates the reverberation time. The reverberation time is calculated using a regression equation of the sound intensity level evolution, that the left and right ear are subjected. The reverberation time is calculated, for the left and right ears, using the necessary time to decay 60 dB from the beginning of the test. The reverberation time concept is used in DL [8] and a application can be seen in Conceição et al [9].

The Auditorium Thermal Modelling calculates the:

 distribution of air temperature inside the spaces, the temperature on the indoor bodies, the

temperature on the transparent bodies and the temperature in the different layers of the opaque surfaces. Applications of this numerical model can be seen in Conceição et al. [10], in school buildings geometry, in Conceição et al. [11], in vehicles, in Conceição and Lúcio [12]), in pyramidal trees;  generation of the geometry of the auditorium. The auditorium geometry, based in a cylindrical

geometry coordinates, is generated through a geometric numerical model. The auditorium considers the side walls, stage walls, back walls, ceiling, floor and steps. The CAD system, used in geometrical systems, is frequently applied in in acoustic phenomena, as in Jablonska and Czajka [13], Pelzer et al. [14] and Th Kouzeleas [15], and in thermal phenomena. In the applications in vehicles, as Qianmu et al. [16], or in buildings, as Robert et al. [17], is also frequent the use also the CAD techniques.

In the Auditorium Acoustic Modelling the direct and diffuse path are considered. The integral Sound Propagation numerical model present the path between the source and the receiver, considering the multi reflections, diffractions and refractions at surfaces of the occupied auditorium, using an image source method. This ray tracing method find the reverberation paths between the source and

the receiver. In this numerical model the manikin mouth is used as source and the left and right ears as used as receivers.

The sound propagation was also developed in Schetelig and Rabenstein [18], Savioja et al.[19], Funkhouser et al.[20], Funkhouser et al [21] and [22] and Taylor et al.[23]. These authors analysed in detail the virtual acoustic environments system.

3. NUMERICAL METHODOLOGY

In this study is developed and applied a virtual auditorium, occupied with a maximum of 168 people, used in the numerical simulations, based in a real auditorium. In the grid generation, each surface is built with four lines and four connection points. Each occupant has a height of 1.7 m and a weight of 70 kg.

In the study one manikin seated in the stage and three manikins seated in the audience was selected to be evaluate the reverberation time (see figure 1). The manikin seated in the stage is used as emissor, while the manikins seated in the audience is used as receptors.

The three manikins seated in the audience and in the auditorium right side:

 the first is seated in the front side of the auditorium;

 the second is seated in the middle side of the auditorium

 the third is seated in the back side of the auditorium.

Figure 1 - One manikin seated in the stage and three manikins seated in the audience, of an auditorium

4. RESULTS

In figure 2, 3 and 4 are presented the acoustic path that the occupant is subjected in the right and left ears. Figure 2 is associated with the manikin seated in front side of the auditorium, figure 3 is associated with the manikin seated in middle side of the auditorium and the figure 4 is associated with the manikin seated in back side of the auditorium. In both figures the acoustical path, represent in auditorium top view, and the evolution of the acoustical level in function to the tine, are presented. In accordance with the obtained results, the floor and seats, the ceiling, the back, and the lateral walls are important in the transmission of the diffuse acoustic. The right wall presents an important contribute to the sound propagation in the right ear, while the left wall present an important contribute to the sound propagation in the left ear. In the table 1 is presented the reverberation time calculated in the right and left ear of the virtual manikin. In this calculus the direct, first, second and third reflections are considered in the numerical calculation.

In this calculation the reverberation time is numerically calculated using a regression of the sound intensity level evolution, using an exponential equation, when the receiver is located in the left

and right ears. Thus, the reverberation time is calculated, for the left and right ears, using the necessary time to decay of 60 dB from the beginning of the test. The reverberation time is calculated when the source is located in the mouth of the occupants and the receiver is located in the left and right ears of other occupants are presented in table 1.

a) b)

2,1

2,1

2,05

2,05

Log(dB) = -0,7305 t + 2,0473

R² = 0,9487

Log(dB) = -0,8951 t + 2,0576

R² = 0,905

Log(dB)

Log(dB)

2

2

1,95

1,95

1,9

1,9

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14

a) b) Figure 2 – Acoustic path that the occupant seated in front side of the auditorium as subjected in the right (a) and left (b) ears.

t (s)

t (s)

a) b)

2,1

2,1

2,05

2,05

2

Log (dB) = -0,7349 t + 2,0492

R² = 0,9161

Log(dB)

Log(dB)

2

1,95

log(dB) = -0,7605 t + 2,052

R² = 0,9349

1,9

1,95

1,85

1,9

1,8

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14

a) b) Figure 3 – Acoustic path that the occupant seated in middle side of the auditorium as subjected in the right and left ears.

t (s)

t (s)

a) b)

2,1

2,1

2,08

2,05

2,06

Log(dB) = -0,9134 t + 2,0523

R² = 0,9423

2,04

Log(dB)

Log(dB)

Log(dB) = -0,6564 t + 2,0445

2

R² = 0,8983

2,02

2

1,95

1,98

1,96

1,9

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14

a) b) Figure 4 – Acoustic path that the occupant seated in back side of the auditorium as subjected in the right and left ears.

t (s)

t (s)

Table 1 – Reverberation time calculated in the right and left ear of the virtual manikin.

Right ear Left ear Front side 1.968 2.418 Middle side 2.400 2.691 Back side 1.943 2.691 In accordance with the obtained results, the mean reverberation time is slightly higher for the left ear than for the right ear. The walls absorption and reflection are very important in this calculation. The lateral and, mainly, the ceiling wall show an important contribute in the reverberation calculation. Thus, in accordance with the obtained results the virtual manikin is very important to evaluate the acoustic asymmetry that the occupants are subjected.

6. CONCLUSIONS

In this work a numerical model is applied in the development of the design of Virtual Binaural Manikin and Auditorium Acoustic Modelling. A virtual binaural manikin is used to evaluate the auditory acoustical asymmetries.

In accordance with the obtained results the mean reverberation time is higher for the left ear than for the right ear, being the walls absorption and reflection are very important in this calculus. The lateral and the ceiling wall show an important contribute in the reverberation calculus asymmetry. Thus, in accordance with the obtained results the virtual manikin is very important to evaluate the acoustic asymmetry that the occupants are subjected.

In the future, more virtual manikins will be used simultaneously in the auditorium. The reflexion in the surrounding surfaces and in the manikin surfaces will be also considered.

7. ACKNOWLEDGEMENTS

The authors would like to acknowledge the support of the project (SAICT-ALG/39586/2018) supported by Algarve Regional Operational Program (CRESC Algarve 2020), under the Portugal 2020 partnership agreement, through the European Regional Development Fund (ERDF) and the National Science and Technology Foundation (FCT).

8. REFERENCES

[1] P. Ole Fanger, “Thermal comfort. Analysis and applications in environmental engineering.,” Copenhagen Danish Tech. Press , 1970. [2] ISO, “ISO 7730: Ergonomics of the thermal environment Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria,” Management , 2005, doi: 10.1016/j.soildyn.2004.11.005. [3] ASHRAE-55, “Thermal environmental conditions for human occupancy,” ANSI/ASHRAE Stand. - 55 , 2017. [4] E. Z. E. Conceiçäo, M. C. G. Silva, and D. X. Viegas, “Air quality inside the passenger compartment of a bus,” J. Expo. Anal. Environ. Epidemiol. , vol. 7, no. 4, 1997. [5] E. Z. E. Conceição and M. Lúcio, “Numerical and subjective responses of human thermal sensation,” Proc. BioEng , 2001. [6] E. Z. E. Conceição, C. I. M. Santiago, M. M. J. R. Lúcio, and H. B. Awbi, “Predicting the air quality, thermal comfort and draught risk for a virtual classroom with desk-type personalized ventilation systems,” Buildings , vol. 8, no. 2, 2018, doi: 10.3390/buildings8020035. [7] E. Z. E. Conceição, M. Lúcio, and J. P. Farinho, “Experimental and numerical study of personalized of ventilation in classrooms desks,” in Proceedings of the 10th International Conference in Rooms, Room Vent, Helsinki, Finland , 2007, pp. 13–15. [8] Diário da República, “Decreto-Lei n. o 96/2008 - Regulamento dos Requisitos Acústicos dos Edifícios,” 2008. [9] E. Z. E. Conceição, M. M. J. R. Lúcio, V. D. S. R. Vicente, and V. C. T. Rosão, “Evaluation of local thermal discomfort in a classroom equipped with cross flow ventilation,” Int. J. Vent. , vol. 7, no. 3, 2008, doi: 10.1080/14733315.2008.11683817. [10] E. Z. E. Conceição, A. R. L. Nunes, J. M. M. Gomes, and M. J. R. Lúcio, “Application of a

school building thermal response numerical model in the evolution of the adaptive thermal comfort level in the Mediterranean environment,” Int. J. Vent. , vol. 9, no. 3, 2010, doi: 10.1080/14733315.2010.11683887. [11] E. Z. E. Conceição, M. C. G. Da Silva, J. C. S. André, and D. X. Viegas, “Thermal behaviour

simulation of the passenger compartment of vehicles,” Int. J. Veh. Des. , vol. 24, no. 4, 2000, doi: 10.1504/IJVD.2000.005199. [12] E. Z. E. Conceição and M. M. J. R. Lúcio, “Numerical study of the influence of opaque external

trees with pyramidal shape on the thermal behaviour of a school building in summer conditions,” Indoor Built Environ. , vol. 19, no. 6, 2010, doi: 10.1177/1420326X10377546. [13] J. Jablonska and R. Czajka, “Cad tools and computing in architectural and urban acoustics,”

Buildings , 2021, doi: 10.3390/buildings11060235. [14] S. Pelzer, L. Aspöck, D. Schröder, and M. Vorländer, “Integrating real-time room acoustics

simulation into a CAD modeling software to enhance the architectural design process,” Buildings , 2014, doi: 10.3390/buildings4020113. [15] S. Th Kouzeleas, “Computational Processes of a Hall Cad Modelisation for Acoustic

Simulation According To Accepted Geometry Format Via Acoustic Software,” 1st Int. Conf. “From Sci. Comput. to Comput. Eng. , 2004. [16] Q. Li, S. Meng, S. Wang, J. Zhang, and J. Hou, “CAD: Command-Level Anomaly Detection

for Vehicle-Road Collaborative Charging Network,” IEEE Access , 2019, doi: 10.1109/ACCESS.2019.2904047.

[17] R. Aish, J. Van Vuren, and M. Walmsley, “Integrated CAD development for building services

engineering,” Comput. Des. , 1985, doi: 10.1016/0010-4485(85)90215-5. [18] T. Schetelig and R. Rabenstein, “Simulation of three-dimensional sound propagation with

multidimensional wave digital filters,” in Proceedings of the 1998 IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP ’98 (Cat. No.98CH36181) , 1998, vol. 6, pp. 3537–3540, doi: 10.1109/ICASSP.1998.679634. [19] L. Savioja, J. Huopaniemi, T. Lokki, and R. Väänänen, “Creating interactive virtual acoustic

environments,” AES J. Audio Eng. Soc , 1999. [20] T. Funkhouser, N. Tsingos, and J.-M. Jot, “Survey of Methods for Modeling Sound

Propagation in Interactive Virtual Environment Systems,” Presence Teleoperators Virtual Environ. MIT Press , pp. 1–53, 2003. [21] T. Funkhouser, P. Min, and I. Carlbom, “Real-time acoustic modeling for distributed virtual

environments,” 1999, doi: 10.1145/311535.311590. [22] T. Funkhouser, I. Carlbom, G. Elko, G. Pingali, M. Sondhi, and J. West, “A beam tracing

approach to acoustic modeling for interactive virtual environments,” 1998, doi: 10.1145/280814.280818. [23] M. T. Taylor, A. Chandak, L. Antani, and D. Manocha, “RESound: interactive sound rendering

for dynamic virtual environments,” in Proceedings of the seventeen ACM international conference on Multimedia - MM ’09 , 2009, p. 271, doi: 10.1145/1631272.1631311.