PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Acoustical Conservative Rehabilitation of St Roque Church,Tollecantto - Goa
Menino Allan S.M. Peter TAVARES1
1Conservation Acoustics - Olinda Goa, Goa

ABSTRACT
St. Roque Church, Tollecantto, Goa originally a Chapel was built in 1883. The conservation of the church
edifice is in progress. Preservation of existing worship ambience is essential in any conservative
rehabilitation of a heritage church. It is crucial to have correct reverberation time in the church so as to allowa simultaneous optimization of the worship space for speech and music. In this design, Reverberation Time(RT60) of a sound signal inside the conserved church is established as a conservation reference parameter.
Ideal Reverberation Time (RT60) for St Roque church was calculated and found to be 1.33 s. Impulse
Response Tests were conducted in the church for three different source positions (original High Altar;Existing Altar; Proposed altar) with recordings done at ten locations. Almost all the recording locations haverecorded a RT60 value of 1.4s. Therefore, the value of measured RT60 = 1.4s is established as a reference
yardstick to monitor the rehabilitative expansion of the church to accomodate another 150 faithful in theworship space.
Keywords: Acoustical conservation, Church, Reverberation Time

1. INTRODUCTION
St. Roque church, Tollecanto, Goa (São Roque Igreja' in Portuguese) was originally a chapel affiliatedto St Francis Xavier Parish church, Velim. The chapel was built in 1883 and erected on June 18, 1885. Thistypical diminuted sanctuary village church of Goa shown in Figure 1, has a modest structure comprising of
three bays and three storeys in Rococo Neo-Roman design (1,2). The nave acoustically couples with adiminuted sanctuary in the east and opens up to the congregation in the west through a coupled narthex on
which seats an acoustically coupled choirloft. The gilded and gold platted Retable and side altars reveal
some shades of neo-Gothic of the late nineteenth century.

Figure 1 – The pre-conservation looks of the façade and worship space within St. Roque church.
The contemporary need of accomodating more faithful in the church for liturgical celebrations
prompted the stakeholders to look at options. One easy option was to build a new edifice or make1

allan.wholysound@gmail.com

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lateral expansions into available circulation space around the church. However, a heritage church
deserves a proper intervention that upholds the historicity and periodic aesthetics of the worship space(3). The intervention needs to be a defining moment for the faithful to celebrate restoration of theirown faith experience (4). A holistic approach as such combines efforts to preserve the existing heritage
character of the church while also exploring into the past to restore essential elements of the church
heritage that have gone missing, with the present need for repairs and rehabilitation of the edifice. This
study is part of a conservation plan presented as an alternative to rehabilitate the existing church forthe present needs while conserving the character defining elements of this heritage church.
Conserving the unique architectural style of the church is imperative while designing a longitudinal
expansion within permissible dimensional ratios.

2. METHODOLOGY
Monaural measurements of acoustical impulse response were carried out in the empty St. Roquechurch, in accordance with ISO 3382 set of standards, for three sound source positions (S1: Retable
High Altar, S2: Existing Altar in Sanctuary and S3: Proposed Altar location under sanctuary arch) andfor ten characteristic receiver locations. However, only those recording locations situated inside thechurch per se, are considered in this study (S1, S2, S3 - in sanctuary, three locations in nave and one innarthex) as shown in Figure 2a.
.

Sanctuary

Sanctuary
Sacristy

S2

Sacristy

S1

S3
ARCH

ARCH

Baptistry

Choir-Loft7

PorticoA) Existing Floor Plan of St. Roque church

NAVESchool Building

6Verandah

5

Baptistry

Confession RoomNAVE
School Building

Verandah4

Choir-Loft

PorticoB) Proposed Floor Plan for St. Roque churchFigure 2 – a) Existing Floor Plan of St. Roque church with marked locations of sound sources (S1,S2, S3) and recording locations (S1, S2, S3, 4, 5, 6, 7)b) Floor plan of the Proposed expanded St. Roque church.

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A passive loudspeaker with built-in powered mixer, Yamaha Stagepas 150 (Yamaha Corporation,Japan) was used. A directional speaker was used to simulate the real life situation in a church where apriest or lector or singer (human voice) is the sound source that emits energy into the worship space.
The loudspeaker was set at an average height of a human person (160 cm) axially oriented towards thenave. Periodic Pink noise of 128k sampling length and 44100Hz sampling rate was used as theacoustical impulse released from the laptop based acoustical software ARTA version 1.9.2(ARTALABS, Croatia and ASIO Interface Technology by Steinberg Media Technologies GmBH)
along with M-AUDIO 2 audio interface (M-Audio, USA) and omnidirectional Behringer ECM8000
measurement microphone (Behringer, Willichm Germany). The recording microphone was set at 160
cm (average height of standing listeners).
The optimum Reverberation time calculations (5,6) were done for the existing St. Roque churchand compared with the measured values of RT60. The possibility of fixing a reference RT 60 value wasexplored while expanding the church to accomodate a larger congregation. The proposed expansion of
the church, as shown in Figure 2b, was done in harmony with the existing bay width of the church andhad to accomodate the reference reverberation criteria. The optimal location for the altar wasidentified from the cumulative spectral decay, RT60 spectral analysis of the possible sound sources,
positional variance of Loudness and Speech Intelligibility (7) and multiregressions of RT60 with othermonaural acoustical measures. The acoustical analysis was done using ARTA 1.9.2, Microsoft Excel
2007 and Origin 6.1.

3. RESULTS
3.1 Cumulative spectral decay at multiple sources
The cumulative spectral decay for the impulses released from sources S1, S2 and S3 is shown inFigure 3, Figure 4 and Figure 5 respectively.

Figure 3 – The cumulative spectral decay at Source 1 (Retable altar location) in St. Roque church.

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Figure 4 – The cumulative spectral decay at Source 2 (Present altar location) in St. Roque church.

Figure 5 – The cumulative spectral decay at Source 3 (Proposed altar location) in St. Roque church.

3.2

Optimum Reverberation Time in a church
Using Sabine's formula for Reverberation time shown in Equation 1,(1)(where, RT60=Reverberation Time in seconds (s); V= volume of the church in cubic feet (ft3); S=
surface area of the church in square feet (ft2); α = Average absorption coefficient of the church in sabinefeet), and Knudsen and Harris' methods (5,6), optimum Reverberation time for St Roque church wascalculated and found to be 1.33 seconds.
3.3 Multi-source positional spectral variance of RT60
The spectral variance of RT60 for S1, S2, and S3 at different recording positions in St. Roquechurch is shown in Figure 6, Figure 7 and Figure 8 respectively.

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Figure 6 – Spectral variance for RT60 at Source 1 (Retable altar location) in St. Roque church.

Figure 7 – Spectral variance for RT60 at Source 2 (Present altar location) in St. Roque church.

Figure 8 – Spectral variance for RT60 at Source 3 (Proposed altar location) in St. Roque church.

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3.4

Multi-source positional variance of Loudness and Speech Intelligibility

The positional variance of Loudness (Leq) and Speech Intelligibility (RASTI) for sources S1, S2and S3 is shown in Figure 9.

Figure 9 – Positional variance for Leq and RASTI in St. Roque church.
a) Positional variance of Leq for Source 1b) Positional variance of Leq for Source 2c) Positional variance of Leq for Source 3e) Positional variance of RASTI for Source 1f) Positional variance of RASTI for Source 2g) Positional variance of RASTI for Source 33.5 Multi-Regressions of RT60 with monaural acoustical measures
The significant (p≤0.05) multi-regressions of RT60 with other monaural acoustical measures atdifferent source locations are shown in Table 1.

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Table 1 – Significant multiregressions of RT 60 with monaural acoustical measures
Rec. Loc.
S1
S2
S3
Rec4
Rec6Rec7PREDICTION EQUATION AT SOURCE 'S1'
RT60 = 2.99 - 0.39EDT + 0.05C80 - 0.04D50 + 0.001TS
RT60 = 1.18 + 0.70EDT - 0.02C80 - 0.004D50 + 0.009TS
RT60 = -2.30 + 1.33EDT+ 0.11C80 + 0.01D50 + 0.01TS
RT60 = 4.45 + 0.78EDT+ 0.18C80 - 0.06D50 - 0.015TS
RT60 = -0.76 + 2.13EDT + 0.29C80 - 0.03D50 + 0.001TS
RT60 = -0.12 + 1.42EDT + 0.07C80 - 0.01D50 - 0.002TS

R20.96
0.97
0.94
0.98
0.98
0.998

p- value
0.004
0.01
0.03
0.007
0.006
0.02

Rec. Loc.
S2S1
Rec4
Rec5
Rec6
Rec7

PREDICTION EQUATION AT SOURCE 'S2'
RT60 = 6.9 - 0.11EDT + 0.02C80 - 0.06D50 - 0.03TS
RT60 = -0.28 + 0.65EDT - 0.06C80 + 0.02D50 - 0.003TS
RT60 = -0.49 + 0.56EDT - 0.10C80 + 0.02D50 + 0.004TS
RT60 = 1.06 + 1.04EDT - 0.04C80 - 0.01D50 - 0.005TS
RT60 = 2.16 + 0.29EDT + 0.03C80 - 0.015D50 - 0.004TS
RT60 = 0.54 + 0.65EDT - 0.1C80 + 0.007D50 - 0.002TS

R2
0.9
0.9
0.98
0.97
0.85
0.93

p- value
0.03
0.03
0.001
0.002
0.05
0.01

Rec. Loc.
S1
S2
Rec5
Rec6
Rec7

PREDICTION EQUATION AT SOURCE 'S3'
RT60 = 0.76 + 1.11EDT - 0.04C80 + 0.0015D50 - 0.007TS
RT60 = 0.56 + 0.56EDT - 0.04C80 + 0.01D50 - 0.002TS
RT60 = 1.18 + 0.83EDT - 0.04C80 - 0.007D50 - 0.006TS
RT60 = 2.23 + 0.63EDT - 0.02C80 - 0.015D50 - 0.01TS
RT60 = 1.42 + 0.9EDT - 0.1C80 - 0.003D50 - 0.01TS

R20.998
0.89
0.96
0.86
0.99

p- value<0.0001
0.03
0.04
0.05
0.0006

4. COMPARISON OF SOUND SOURCES IN ST. ROQUE CHURCHThe cumulative spectral decay at the Retable High altar location (Source 'S1') indicates a follow up
of small magnitude in the frequency range of 1kHz - 2kHz upto around 60-70 ms. This improves at theexisting altar location (Source 'S2') whereas at the proposed altar location (Source 'S3') the follow up
restricts to a window of 30-40 ms. This suggests more strength and intelligibility in the signal emitted
from 'S2' (cf. Figures 3-5).
At Source 'S1' impulse, RT60 showed assymetric higher values in the frequency bands of 63 Hz &125 Hz (ranging from 1.7s - 2.1s) at Recording location'5' (in the middle of the nave) while averaging
1.29 seconds in the church. At Sources 'S2' and 'S3' impulses, RT60 showed a more uniform behaviour
with the space responding a little more reverberantly, averaging 1.42 seconds in the church (for boththe sources) Noteworthy observation is of the immediate frontal recording position 'S3' being the mostreverberant (in most spectral bands) for Source 'S2' (cf. Figures 6-8).
While the impulse response at the back of the nave and in the narthex is quieter (in terms of Leq) for
impulses from sources 'S1' and 'S2', the sanctuary becomes quiet for the impulse from source 'S3' (cf.
Figures 9 a-c). The impulse from the existing altar location (Source 'S2') elicits comparatively betterspeech intelligibility (in terms of RASTI) in the nave and the sanctuary averaging 0.57 in the church(cf. Figures 9 d-e).
RT60 showed significant (p≤0.05) positive correlation with C80 and TS and showed significant
negative correlation with EDT and D50 for source 'S1' recording at source point (S1). RT60 showedsignificant positive correlation with C80 and showed significant negative correlation with EDT, D50
and TS for source 'S2' recording at source point (S2). However at source 'S3', RT60 could not be
predicted significantly from the monaural acoustical measures recording at source point (S2) and atrecording position '4' (front-nave space). RT60 did not regress significantly with the monaural
acoustical measures also at source 'S1' for Recording position '5' (mid-nave space).

5. CONCLUSIONS
Looking at the cumulative spectral decay at each source and the spectral behavior and significant3965

multi-regressions of RT60 along with the wide band values of RASTI and Leq, the source 'S2' (existingaltar location) seems to provide a better acoustical climate in the church in terms of good reverberance
coupled with speech intelligibility and adequate loudness. Therefore, it is recommended to retain thealtar location to its existing position.
As the average value of measured RT60 inside the church across all the sources was found to be
1.38 s, the conservative expansion of the church was monitored to keep the calculated reverberation
inside the church within 1.40 seconds. The optimum reverberation time calculations (5, 6) for the
proposed plan infact provides a RT60 value of 1.38 seconds. In this conservative plan, the width of thechurch (9.1m) is retained; importing the existing roof style of the sanctuary, the flat wood panelledfalse roofing of the nave at a height of 6.8m is changed into a trapezoidal wood panelled vault
beginning at a height of 6.8m (on the eves) from the cornice level merging into a flat wood panelledplain/coffered roof at a maximum height of 7.9 m - this gentle raising of height negates the 'low ceiling'effect in the nave and the choir loft space; the length of the nave (inclusive of the narthex) is increased
from 14.4m to 20.6m; Thus, the length/heigth ratio of the nave changes from 2.10 to 2.61; theheigth/width ratio of the nave changes from 0.75 to 0.87 and the length/width ratio of the nave changes
from 1.57 to 2.26. The number of pews in the nave and the narthex of the church consequently increase
from 26 to 38. This increase in pews will allow nearly 80 - 90 more faithful (calculating 8persons/pew) in the nave and the narthex of the church. Atleast another 70 - 80 faithful will beaccomodated in the additional 10 pews in the choirloft. In total, about 150 - 170 more faithful will thus
get accomodated inside the proposed expanded church while retaining the acoustical worshipambience characterized by a reverberance of about 1.4 seconds.
Thus a thorough multi-source spectral investigation of reverberation as reflected by RT60 inrelationship with other monaural acoustical measures was used as a working tool to acousticallyconserve the worship ambience and aesthetics of St. Roque church while expanding it to accomodate
more congregation. This investigation also endorsed the presently used altar position as theacoustically correct location for the altar in the church.

ACKNOWLEDGEMENTS
We acknowledge gratefully, Society of Pilar, Goa, Most Rev. Filip Neri Archbishop of Goa and Parish
Priest and Fabrica of St. Roque church, for permission to pursue this research. We are grateful toGovernment of Goa, Nadja Haeberle, Cedric and Kristel, Fr. Joaquim Fernandes sfx and friends inGermany for supporting the presentation of this paper at ICA 2019, Aachen.
We are appreciative of our team: Paxton Fernando (Martha Developers), Arch. Sarvesh Naik,Nixon Fernandes, Anthony Miranda, Mankam Mossang and all the experts and artisans involved in theconservation of St. Roque church.

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3. Tavares MAPS, Carvalho APO, Rajagopalan S, Sharma SJ, Nachinolkar K, Lourenço J. PreRestoration characterization of Acoustical Heritage of Nossa Senhora do Pilar church, Goa. In: Gettu
R, Santhanam M, Menon A, Pillai RG, editors. Rehabilitation and Restoration of Structures. Chennai,India: IIT Madras; 2013.p. 335 - 345.
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6. Knudsen VO, Harris CM. Acoustical Designing in Architecture. USA: American Institute of Physics;
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