Creation and calibration method of acoustical models for historic virtual reality auralizations

Abstract

Virtual reality provides the possibility for interactive visits to historic buildings and sites. The majority of current virtual reconstructions have focused on creating realistic virtual environments, by concentrating on the visual component. However, by incorporating more authentic acoustical properties into visual models, a more realistic rendering of the studied venue is achieved. In historic auralizations, calibration of the studied building’s room acoustic simulation model is often necessary to come to a realistic representation of its acoustical environment. This paper presents a methodical calibration procedure for geometrical acoustics models using room acoustics prediction programs based on geometrical acoustics to create realistic virtual audio realities, or auralizations. To develop this procedure, a small unfinished amphitheater was first chosen due to its general simplicity and considerable level of reverberation. A geometrical acoustics model was calibrated according to the results of acoustical measurements. Measures employed during the calibration of this model were analyzed to come to a methodical calibration procedure. The developed procedure was then applied to a more complex building, the abbey church Saint-Germain-des-Prés. A possible application of the presented procedure is to enable interactive acoustical visits of former configurations of buildings. A test case study was carried out for a typical seventeenth-century configuration of the Saint-Germain-des-Prés.

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Notes

  1. 1.

    https://www.oculus.com.

  2. 2.

    http://www.mathworks.com.

  3. 3.

    While CATT-Acoustic offers special algorithms using deterministic scattering, these are intended for open space cases or rooms with high and uneven absorption, neither of which is the case in the rooms considered here.

  4. 4.

    To optimize computation time, this step was first carried out using the option interactive estimate in CATT-Acoustic, which runs a rapid global ray-tracing. Subsequently, the basic algorithm for closed rooms was used (option: short calculation, basic auralization) to create RIRs and refine the calibration.

  5. 5.

    Since the measured SNR in the 125-Hz octave band was less than 45 dB, T30 could not be calculated. Therefore, only T20, EDT, C50, and C80 are considered for this case.

  6. 6.

    Due to the very high direct-to-reverberant ratio, caused by the close proximity to the source, measurement configurations with source 2 for receiver positions 29 and 30, as defined in Fig. 5, were omitted from further analysis. A high direct-to-reverberant ratio results in an unrealistically steep early decay which confounds the reliability of parameter assessment.

  7. 7.

    These plots are results from the internal CATT-Acoustic parameter mapping. This stands in contrast to the previously presented results which were based on RIR analysis.

  8. 8.

    The \(\Delta [\cdot ]\) notation employed here denotes the difference in resulting values over the six octave bands.

References

  1. Ahearn M, Schaeffler M, Celmer R, Vigeant M (2008) Investigation of the just noticeable difference of the clarity index for music, C80. J Acoust Soc Am 126(1):2288

    Google Scholar 

  2. Alonso A, Sendra J, Suárez (2014) Sound space reconstruction in the cathedral of Seville for major feasts celebrated around the main chancel. In: Proceedings of the forum acusticum

  3. Angelini D, Milan N (2010) 3d and 2d documentation and visualization of architectural historic heritage. In: Proceedings of the CIPA symposium

  4. Beranek L (1986) Acoustics. Acoustical Society of America, New York

  5. Beranek L (1996) How they sound concert and opera halls. Acoustical Society of America, New York

  6. Bibliothèque national de France (1898) Plans manuscrits de l’église de Saint-Germain-des-Prés, en 1644, “l’année de son rétablissement” [Plan documents of the abbey of Saint-Germain-des-Prés in 1644 “year of reinstatement”]. In: Annales de l’abbaye de Saint-Germain-des-Prés (555–1743), et pièces annexes jusqu’en 1753. MS. FR. 18816, FOL. 72, vol 265, Fondation de L’Abbey. http://gallica.bnf.fr/ark:/12148/btv1b9058114j/f72.image

  7. Bradley J, Reich R, Norcross S (1999) A just noticeable difference in C50 for speech. Appl Acoust 58(1):99–108

    Article  Google Scholar 

  8. Busson D, Ferrand F (2012) Paris, la ville à remonter le temps. Flammarion, Paris

    Google Scholar 

  9. Copper G, Tanan J (2015) An immersive labyrinth. In: Proceedings of the IEEE-VR

  10. Cox T, Davies W, Lam Y (1993) The sensitivity of listeners to early sound field changes in auditoria. Acustica 79(1):280–284

    Google Scholar 

  11. Cox TJ, D’Antonio P (2009) Acoustic absorbers and diffusers: theory design and application. CRC Press, Boca Raton

    Google Scholar 

  12. Dalenbäck B (2010) Engineering principles and techniques in room acoustics prediction. In: Baltic-Nordic. Acoustics Meeting. http://www.catt.se/BNAM-Bergen-2010-CATT.pdf

  13. Dalenbäck B (2011) CATT-A v9: user’s manual CATT-Acoustic v9. CATT, Gothenburg

    Google Scholar 

  14. Dassault Systems (2015) Paris 3d. http://paris.3ds.com/. Accessed 30 April 2015

  15. Environmental Simulation Center (2014) Virtual new Amsterdam prototype. http://www.newamsterdamhistorycenter.org/vnap. Accessed 15 April 2015

  16. Farina A (2000) Simultaneous measurement of impulse response and distortion with a swept-sine technique. In: Proceedings of the 108th AES convention, London, UK

  17. Freiheit, R. (2010) Creating an anechoic choral recording. In: Proceedings of the international symposium on room acoustics

  18. Garcia F, Planells A, Cerdá S, Montell R, Giménez A (2014) Archeological acoustics of the venue of the “Misteri d’Elx” oral and intangible cultural heritage (UNESCO): “Basilica de Santa Maria de Elche”. In: Proceedings of forum acusticum

  19. Grillon V, Meynial, X, Polack, J-D (1995) Auralization in small-scale models: extending the frequency bandwidth. In: Proceedings of the 98th AES convention

  20. ISO 17497 (2007) Acoustics—sound-scattering properties of surfaces—part 1: measurement of the random-incidence scattering coefficient in a reverberation room (ISO 17497-1:2004); part 2: measurement of the directional diffusion coefficient in a free field (DIS 2007). International Organization for Standardization

  21. ISO 3382-1 (2009) Acoustics—measurement of room acoustic parameters—part 1: performance spaces. International Organization for Standardization

  22. James A (2003) Results of the NPL study into comparative room acoustic measurement techniques part 1, reverberation time in large rooms. Proc Inst Acoust 25:4

    Google Scholar 

  23. James A (2004) Results of the workshop on room acoustics measurements. Tech. Rep. 9558/2, NPL. http://www.adrianjamesacoustics.co.uk/technicalstuff/nplreport.pdf

  24. Katz BFG (2000a) Acoustic absorption measurement of human hair and skin within the audible frequency range. J Acoust Soc Am 108(5):2238–2242. doi:10.1121/1.1314319

    Article  Google Scholar 

  25. Katz BFG (2000b) Method to resolve microphone and sample location errors in the two-microphone duct measurement method. J Acoust Soc Am 108(5):2231–2237. doi:10.1121/1.1314318

    Article  Google Scholar 

  26. Katz BFG (2001) Boundary element method calculation of individual head-related transfer function. II. Impedance effects and comparisons to real measurements. J Acoust Soc Am 110(5):2449–2455. doi:10.1121/1.1412441

    Article  Google Scholar 

  27. Katz BFG (2004) International round robin on room acoustical response analysis software 2004. J Acoust Soc Am 4:158–164. doi:10.1121/1.1758239

    Google Scholar 

  28. Katz BFG, Wetherill E (2005) Fogg art museum lecture room, a calibrated recreation of the birthplace of room acoustics. In: Proceedings of forum acusticum

  29. Katz BFG, d’Alessandro C (2007) Directivity measurements of the singing voice. In: 19th International congress on acoustics. https://www.researchgate.net/publication/236213215_Directivity_measurements_of_the_singing_voice

  30. Kleiner M, Dalenbäck BI, Svensson P (1993) Auralization-an overview. J Audio Eng Soc 41(11):861–875

    Google Scholar 

  31. Lokki T, Järveläinen H (2001) Subjective evaluation of auralization of physics-based room acoustics modeling. In: Proceedings of the international conference on auditory display

  32. Lokki T, Svensson P, Savioja L (2002) An efficient auralization of edge diffraction. In: Audio engineering society conference: 21st international conference: architectural acoustics and sound reinforcement. http://www.aes.org/e-lib/browse.cfm?elib=11207

  33. Martellota F, Morales L (2014) Virtual acoustic reconstruction of the church of Gesú in Rome: a comparison between different design options. In: Proceedings of forum acusticum

  34. Martelotta F, Castiglione M (2011) On the use of paintings and tapestries as sound absorbing materials. In: Proceedings of forum acusticum

  35. McDermott S, Chu C (2007) An exploration of virtual 3D sound. 122:3050. http://acoustics.org/pressroom/httpdocs/154th/mcdermott.html

  36. Pedrero A, Daz-Chyla A, Daz D, Pelzer S, vorländer M (2014) Virtual restoration of the sound of the hispanic rite. In: Proceedings of the forum acusticum

  37. Pulkki V, Lokki T (2003) Visualization of edge diffraction. Acoust Res Lett Online 4(4):118–123. doi:10.1121/1.1605131

    Article  Google Scholar 

  38. Rébillat M, Hennequin R, Corteel E, Katz BFG (2010) Prediction of harmonic distortion generated by electro-dynamic loudspeakers using cascade of hammerstein models. In: 128th Convention of the audio engineering society

  39. Seraphim H (1958) Untersuchungen uber die unterschiedsschwelle exponentiellen abklingens von rauschbandimpulsen. [Investigations about the difference threshold in exponential decay of noise band pulses]. Acustica 8(1):280–284

    Google Scholar 

  40. Tuytel R (2013) Amsterdam—the golden age experience. In: Blender conference 2013. http://www.degoudeneeuw3d.nl/. Accessed 17 April 2015

  41. Tuytel R (2014) Using blender and unity for oculus game environments. In: Blender conference 2014. http://www.degoudeneeuw3d.nl/. Accessed 17 April 2015

  42. Vorländer M (2008) Auralizations fundamentals of acoustics, modeling, simulation, algorithms and acoustic virtual reality. Springer, Berlin

    Google Scholar 

  43. Vorländer M (2010) Prediction tools in acoustics—Can we trust the PC? In: BNAM

  44. Weitze C, Christensen C, Rindel J (2001) Computer simulation of the acoustics of mosques and byzantine churches. In: Proceedings of the ICA

  45. Wright C (2008) Music and ceremony at the Notre Dame of Paris. Cambridge University Press, Cambridge

    Google Scholar 

  46. Zeng X, Christensen C, Rindel J (2006) Practical methods to define scattering coefficients in a room acoustics computer model. Appl Acoust 67:771–786

    Article  Google Scholar 

Download references

Acknowledgments

The authors would like to thank the personnel of the Saint-Germain-des-Prés for their help in organizing the acoustic measurements, Daniel Furlan for his overall help during the Project, and Andrew Tallon of Vassar College for his advice concerning the historic configuration of the Saint-Germain-des-Prés. Thanks to Bengt-Inge Dalenbäck, CATT-Acoustic, for the numerous and lengthy informative discussions. Final thanks are for the 3D laser scan, provided by Andrew Tallon, and the architectural plans and sections, provided by Pierre Bloy Géometre-Expert D.P.L.G., architects of a recent renovation of said building.

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Correspondence to Barteld N. J. Postma.

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This work was funded in part by the ECHO Project (ANR-13-CULT-0004, echo-projet.limsi.fr). Partners include THALIM/ARIAS-CNRS, Bibliothèque nationale de France (BnF), and LIMSI-CNRS.

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Appendices

Appendix 1: Details of amphitheater calibration

This section details steps 4–6 of the calibration procedure for the amphitheater. Table 2 shows the absorption coefficients, \({\mathrm{char}}_{\mathrm{depth}}\) used in the first iteration, and the associated surface areas which were concluded from the material search as proposed in step 1.

Table 2 Absorption coefficients, \({\mathrm{char}}_{\mathrm{depth}}\) (mm) as the single value which was inserted into Eq. (1), and surface area (m\(^2\)) used in the initial iteration of the amphitheater

Curve initial in Fig. 14 shows the average T20 and C50 which resulted from the use of the material properties presented in Table 2. Subsequently, the absorption coefficients of the Aluminum (walls) and aluminum (ceiling), the materials most used in the amphitheater, were iteratively adjusted to arrive at [0.168, 0.150, 0.099, 0.072, 0.080, 0.072], bringing EDT and T20 within 1 JND, as depicted by Curve step 4 in Fig. 14.

Fig. 14
figure14

Evolution of mean T20 and C80 during the calibration procedure as compared to the mean measured (\(\pm 1\) JND) values

Curve step 4 in Fig. 14 shows that the mean C50 was \(\Delta\)[\(-0.49\), +0.21, +0.33 +0.32, +0.60, 0.50 dB].Footnote 8 Since Fig. 6 showed that increasing the scattering resulted in a lower clarity, the \({\mathrm{char}}_{\mathrm{depth}}\) of the aluminum (walls) was increased to 55 mm, the \({\mathrm{char}}_{\mathrm{depth}}\) of the plaster board was increased to 10 mm, the \({\mathrm{char}}_{\mathrm{depth}}\) of the concrete (floor and wall) was increased to 20 mm, and the \({\mathrm{char}}_{\mathrm{depth}}\) of the concrete (ramp) was increased to 20 mm. To raise the mean C50 in the 125-Hz octave band, the scattering in this octave band of these surfaces was set to 5 %. Furthermore, the edge diffusion of the objects was omitted, and the metal construction was modeled with edge diffusion. Curve step 5 shows that after these adjustments the mean difference between measured and simulated C50 changed to \(\Delta\) [\(-0.33\), +0.06, +0.39, +0.20, +0.50, 0.35 dB] which is an improvement across all octave bands except for 1000 Hz.

At the start of step 6, the SD determined over the positions’ difference between measured and simulated T20 was [0.29, 0.18 s] and EDT was [0.44, 0.25 s]. A decrease in these values means a better estimation of the parameters per position. Therefore, a search was conducted for positional differences. It was found that the receivers on the upper mezzanine (R11–15) overestimated the T20 [125, 250 Hz] with \(\Delta\)[+0.14, +0.02 s], while the receivers on the lower mezzanine underestimated this with \(\Delta\)[0.15, 0.06 s]. Since the receivers on the upper mezzanine were closer to the objects and plaster boards, their absorption coefficients were raised to arrive at, respectively [0.25, 0.12] and [0.17, 0.12], while the absorption of the aluminum (walls) and aluminum (ceiling) was lowered to [0.156, 0.146] to retain the same mean reverberation and clarity. After these adjustments, the receivers on the upper mezzanine overestimated the T20 by \(\Delta\)[+0.11, +0.02 s], while the receivers on the lower mezzanine underestimated the T20 by \(\Delta\)[\(-0.11\), \(-0.03\) s]. This resulted in a lower SD of the T20 [0.25, 0.15 s] and EDT [0.37, 0.25 s] and therefore a better estimation of these parameters per position. Curve step 6 shows the resulting mean T20 and C50.

With the calibrated GA model, the initially chosen material properties are compared to those used in the final model. The difference between originally and finally modeled absorption coefficients of the aluminum panels is because the initial values were adopted from data concerning nonperforated aluminum panels on a 300-mm airspace measured in a reverberation chamber. However, in the amphitheater, insulation material is installed behind the aluminum panels. Therefore, the actual absorption properties of the aluminum panels differ from the initially simulated values. The absorption of the objects is difficult to estimate due to the uncertainty in used material and possible panel absorbing properties due to their hollow interior. Beside the change in absorption coefficients, the scattering coefficients for the concrete, plaster board, and aluminum panels were decreased in the 125-Hz octave band, and those of the aluminum (walls), concrete, and plaster board were increased. As the concrete, plaster board, and aluminum panels are large flat surfaces and consequently the surface size is large in relation to the wavelength, it is justified to adopt a scattering of 5 % in the 125-Hz octave band. Furthermore, raising the \({\mathrm{char}}_{\mathrm{depth}}\) of the aluminum (walls) can be justified by the metal construction in front of the wall which makes the wall more diffusing in the higher octave bands than initially assumed, and increasing the \({\mathrm{char}}_{\mathrm{depth}}\) of the concrete and plaster board is justified by the objects in front these which makes it more diffusing than originally assumed. Additionally, probably for similar reasons, we note that the general guidelines in the CATT-Acoustic manual recommend that it is better to overestimate scattering coefficients than to underestimate them (Dalenbäck 2011, p. 111) (Table 3).

Table 3 Absorption coefficients, \({\mathrm{char}}_{\mathrm{depth}}\) (mm) as the single value which was inserted into Eq. (1), and assigned surface area (m\(^2\)) used in the calibrated model of the amphitheater

Appendix 2: Details of Saint-Germain-des-Prés calibration

This section details steps 4–6 of the calibration procedure for the Saint-Germain-des-Prés. Table 4 depicts the absorption coefficients, \({\mathrm{char}}_{\mathrm{depth}}\), and surface area assigned to these materials, in first iteration. Curve initial in Fig. 15 shows the average EDT and C80 of the first iteration.

Table 4 Absorption coefficients, \({\mathrm{char}}_{\mathrm{depth}}\) (mm) as the single value which was inserted into Eq. (1), and surface area (m\(^2\)) used in the initial iteration of the Saint-Germain-des-Prés
Fig. 15
figure15

Evolution of mean EDT and C80 during the calibration procedure as compared to the mean measured (\(\pm 1\) JND) values

The average T20 and EDT were brought within 1 JND of the measured value by adjusting the absorption coefficient of the painted plaster to [0.010, 0.019, 0.028, 0.032, 0.038, 0.037], since this material represents the largest surface area and therefore has a principal influence on the acoustic response. Curve initial in Fig. 15 shows the average EDT came within one JND after the absorption coefficient was lowered, concluding step 4.

Figure 8 shows that by increasing the scattering, the clarity parameters in the octave bands 500–4000 Hz became lower and vice versa. Curve step 4 in Fig. 15 shows that at this stage the C50 differed \(\Delta\)[\(-1.35\), 0.25, \(-0.26\), 0.98, 1.60, 0.52] from the measurements. Since the clarity in the higher octave bands needed to decrease, the \({\mathrm{char}}_{\mathrm{depth}}\) was increased to 300 mm for the columns, to 10 mm for the floor, to 55 mm for the walls, and to 55 mm for the ceiling. Additionally, the absorption coefficients of the painted plaster in octave band 2000 Hz was lowered to 0.035. Furthermore, since Fig. 8 did not give an answer how to raise the C50 in the lower octave bands, iteratively adjusting various parameters resulted in finally adding edge diffusion to the columns and raising the absorption of the painted plaster [125, 250, 500 Hz] to [0.013, 0.022, 0.032]. Curve step 5 in Fig. 15 shows that the combination of these measures resulted in a C50 \(\Delta\)[\(-1.01\), 0.03, \(-0.29\), 0.87, 1.43, 0.43], which better estimated the measurement across all octave bands, except in the 500 Hz where it remained approximately the same.

The main adjustments in the GA model’s surface properties were the adjustment of the plaster surfaces’ absorption coefficient as well as the raising of the \({\mathrm{char}}_{\mathrm{depth}}\) of the limestone and plaster surfaces. Various reasons can explain the difference between the initial and final modeled absorption coefficients of the plaster surfaces. In the initial iteration, these values were adopted from the material Concrete block, plastered; in the calibrated model, the absorption coefficient more resembles the material Walls, hard surface average (brick walls, plaster, hard floors) [0.02, 0.02, 0.03, 0.03, 0.04, 0.04] found in Vorländer (2008). Since these are both reasonable choices for the absorption coefficient, it can be stated that these fall within the range found in step 1 of the methodological calibration. There are additional reasons why absorption coefficients can differ from the databases: Materials may have experienced transformations due to aging (Garcia et al. 2014). Additionally, probably because the size of elements high in the Saint-Germain-des-Prés is difficult to gauge during a visual inspection, these were underestimated in the initial iteration. This has influenced the estimation of the \({\mathrm{char}}_{\mathrm{depth}}\) of the plaster wall, limestone, plaster arch, and plaster ceiling, which were underestimated in the initial iteration, explaining the increased \({\mathrm{char}}_{\mathrm{depth}}\). Furthermore, because the plaster column has a small size in relation to the wavelength, the addition of the edge diffusion is justified (Table 5).

Table 5 Absorption coefficients, \({\mathrm{char}}_{\mathrm{depth}}\) (mm) as the single value which was inserted into Eq. (1), and surface area (m\(^2\)) used in the final iteration of the Saint-Germain-des-Prés

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Postma, B.N.J., Katz, B.F.G. Creation and calibration method of acoustical models for historic virtual reality auralizations. Virtual Reality 19, 161–180 (2015). https://doi.org/10.1007/s10055-015-0275-3

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Keywords

  • Auditory VR
  • Calibration
  • Acoustic archeology
  • Auralization
  • Geometrical acoustics
  • Virtual heritage