PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Mapping the acoustics of Ripon cathedral
Lidia ALVAREZ-MORALES1; Mariana LOPEZ2; Angel ALVAREZ-CORBACHO3; Pedro
BUSTAMANTE4
1,2
3, 4

University of York, Department of Theatre, Film, Television and Interactive Media, UK

Universidad de Sevilla, Instituto Universitario de Arquitectura y Ciencias de la Construcción, Spain

ABSTRACT
Cathedrals are amongst the most significant buildings of European cultural heritage and are of greatsignificance for the study of intangible heritage. This paper presents a detailed acoustic study of Ripon
Cathedral, an English medieval cathedral whose history goes back to the 7th Century. Experimental andsimulation techniques have been applied in order to develop a better understanding and preservation of theacoustic environment of Ripon cathedral. This research addresses the acoustical conflict inherent to this kindof spaces: its extreme reverberation builds a unique environment for vocal and instrumental music, speciallyorgan music, but at the same time those same characteristics are a challenge for the intelligibility of the
spoken word, which is crucial to the delivery of sermons. Acoustic maps have been created based on thediverse uses of the space, the history of the building, and its architectural features. Such maps have been used
to analyse the acoustic characteristics throughout the cathedral’s interior space. This work is part of the ECfunded Marie-Sklodowska- Curie Fellowship ‘Cathedral Acoustics’.
Keywords: Church acoustics, Room impulse responses, Acoustic simulation

1. INTRODUCTION
Cathedral Acoustics is a project which aims to study the acoustics of a diverse sample of English
cathedrals by focusing on four examples: Bristol, Ely, Ripon and York, which were chosen in relation
to their historical classification, their ground plan typology as well as architectural style. The aim of
the project is to study the current acoustic characteristics of the buildings through Room Impulse
Response measurements (RIR) as well as work with computer simulations to study how structural,
ornamental and usage changes would have affected the acoustics of the space throughout history.
Research on the acoustics of heritage sites is of the utmost importance for two main reasons. Firstly,
it allows us to preserve the acoustics of the spaces which may be threatened by restoration work andallows us to store that information to help us preserve the intangible heritage of these buildings forposterity and to aid refurbishing work. Secondly, understanding how the acoustic conditions changed
over time allows us to study what this might have meant for our ancestors, including how this may
have affected changes in the use and experience of the space.
The present paper focuses on an initial study of Ripon Cathedral, which is conducted both throughacoustic measurements as well as a computer simulation of the space. This preliminary study includes
an overview of the methodology utilised, including the historical data that informed the measurement
and simulation decisions and an analysis of the results based on reverberation time (T 30 , EDT),
musical clarity (C 80 ) and speech intelligibility (STI) parameters.

1

lidia.alvarezmorales@york.ac.uk
mariana.lopez@york.ac.uk
3arqangel@us.es
4bustamante@us.es
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2. RIPON CATHEDRAL
2.1 An overview of the construction process
The history of Ripon Cathedral dates back to the 7th century. The present building is raised over
the oldest Saxon crypt in England (1), which was part of the original church of St. Wilfrid, which waserected on the site of the monastery of Ripon, founded by Scottish monks in the 660s.
Successive reconstructions and extensions have resulted in different architectural styles coexistingin the building. The construction of the present cathedral began in 1154 incorporating part of theoldest structure in Early English Gothic style. Subsequently, Archbishop Walter de Gray (1216-1255)
continued the works by constructing the current west façade and the two towers that flank it, as wellas the tall wooden spires and lead covers that once topped the towers. At the end of the 13th century,
the eastern part of the choir was reconstructed in Decorated English style. The most important
modification in the 14th century was the construction of the Lady Chapel over the Chapter House (2),which has now become the Cathedral Library. In the 16th century, the aisles were erected in
Perpendicular style.
2.2 Description of the interior
As many other English cathedrals, Ripon cathedral has a Latin Cross shape, although in thisparticular case the single transept is only slightly longer than the nave width, as can be seen in Figure
1. The nave (41.7 meters long from the west doors to the transept) has two almost alike lateral aisles
demarcated by Perpendicular-style gritstone pillars and a stone ribbed vault on top (3). From thosepillars, the arches that hold the oaken vault that covers the central nave (at a height of 24.9 m) emerge.
The nave, surrounded by stained glasses, is austere in decoration.
Notable is the "art nouveau" pulpit dated from 1913, which stands on marble pillars and has silver
and bronze ornamentation. From the pew area of the nave it is possible to view the colourful stone
carved Rood screen and the organ (Figure 2, left). Such a wide and closed screen serves as a soundand visual barrier, being originally raised to separate clergy from seculars (2). Beyond the screen is
the choir, where many architectural styles meet: Norman–Gothic Transitional, Perpendicular, andDecorated. The carved oak choir stalls are surmounted by lofty canopies. The chancel area is 30.4 m
long, from the screen door to the east window presiding the Main altar (Figure 2, right). The presbytery
is separated from the lateral aisles by light wooden screens, except in the south part of the altar, wherea stone sedilia is found.

Figure 1 – Floor plan of Ripon cathedral with the source (S) and receiver (R) positions set for the acoustic
measurements and the acoustic simulations.

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Figure 2 – Interior views of Ripon cathedral: View of the roodscreen from the main nave (left) and view ofthe east end wall from the choir stalls (right).

3. METHODOLOGY OF ANALYSISThe acoustic study of Ripon cathedral presented in this paper is based on the analysis of the room
impulse responses registered on site. Furthermore, simulation techniques are used to complete theanalysis and create the acoustic mappings of the nave space.
3.1 Acoustic measurements
The acoustic measurements follow ISO3382-1 (4) as well as considering the specific guidelines
developed for similar buildings (5,6). Sine-sweeps of a duration of 13 seconds covering a frequency
range from 50 Hz to 16 kHz were emitted through a dodecahedral loudspeaker (NTi DS3 loudspeaker
together with a NTi PA3 power amplifier) placed in multiple positions. Up to 31 receiver positions
were chosen throughout the congregation area. For each source-receiver combination a set of RIR(Room Impulse Responses) were captured by using a B-format microphone (Soundfield ST450) andan artificial head (Neumann KU 100). The digital audio workstation Pro Tools 12 and MATLAB
software were used to capture and process the signals respectively. EASERA software was used forthe acoustic analysis and the calculation of the acoustic parameters. All the instrumentation and data
analysis methods are ISO3382-1 compliant.
Source and receiver positions were selected based on the diverse uses of the space, the history of
the building, and its architectural features. Ripon cathedral’s interior is physically divided by theroodscreen, and therefore, the nave, the transepts and the chancel were characterised independently.
Binaural and B-format RIR were measured at receiver positions from R01 to R11 and R29 to R31 withthe sound source placed in the Nave’s Altar (SN), where mayor liturgical celebrations and instrumental
and choral concerts are held on a regular basis. In the chancel, receiver positions 12 and 10 werecharacterised with the source located in the choir (SC) and at the presbytery (SA), respectively. Figure
1 shows the floor plan of Ripon cathedral with source (S) and receiver (R) locations set during themeasurement session. Although it would have been of interest to study the effect of sources locatedat the pulpit and at the lateral chapels, this was not possible due to access and time restrictions.
3.2 Acoustic Simulation
The acoustic simulation of Ripon cathedral was completed using the software CATT-Acoustic™
v9.1b powered by TUCT™ v2.0a (7). Simulations were run with TUCT Algorithm 1: Short calculation,
basic auralization using transition order 1, with 300,000 rays. Source and receiver positions were
simulated corresponding to the ones set during the measurements.
Due to the physical division of the space and for the purpose of this paper, the acoustic model has
been simulated in two parts: on the one hand, the space formed by the nave and the transept, and on
the other, the chancel. The openings that actually communicate both spaces, which cover a total areaof 108 m2 (green surface in the model, Figure 3), have been considered as an “open” surface with anabsorption coefficient close to one at all frequency bands, i.e. almost total acoustic absorption. Thisdecision was made to simplify the model and reduce the calculation time, having note that the number2337

of rays that returned from the choir space to the nave during some preliminary tests was despicable inthe sense that results of the acoustic parameter values at the S-R combinations analysed in the nave
were not significantly affected by this simplification. Figure 3 shows the simplified acoustic modelof the cathedral nave, which also includes the transept, used to carry out the acoustic simulation
presented in this paper. The model has 2,836 planes and an approximate volume of 31,000 m3 .
The acoustic properties of each finishing material (represented by the different colours in themodel) are given by the corresponding absorption and scattering coefficients (see Table 1). The initialabsorption coefficients were obtained from the literature (8,9). The scattering coefficients wereassigned depending on the complexity and the degree of decoration of each surface. For those surface
materials whose absorption and scattering coefficients were more complex to determine, the researchteam worked on a careful tuning process that compared measured and simulated room impulse
responses and acoustic parameter values in order to determine the most appropriate values. The
porosity of the gritstone and the degree of decoration of some of the surfaces with this material, haverequired an increase in the values initially assigned according to bibliography (8). This uncertainty inthe construction/finishing materials is inherent to these heritage spaces, and comparable results has
already been obtained in similar buildings (10). Other finishing materials, such as the wooden vault,
has also required a moderate adjustment at certain octave bands (See Table 1).

Figure 3 – Acoustic model of the nave of Ripon cathedral
Table 1 – Acoustic property of materials used in the acoustic model
Material Name

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Colour

Absorption/Scattering coefficients

Area
(%)

125 Hz250 Hz500 Hz

1 kHz

2kHz

4 kHz

Gritstone walls

61.2 0.08/0.12 0.08/0.13 0.09/0.14 0.09/0.15 0.09/0.16 0.09/0.17

Rough ceramic floor

10.8 0.02/0.10 0.02/0.10 0.02/0.10 0.02/0.10 0.02/0.10 0.02/0.10

Wooden vault

5.1

0.17/0.10 0.17/0.10 0.10/0.15 0.10/0.15 0.10/0.20 0.08/0.20

Stone ribbed vaults

4.5

0.08/0.20 0.08/0.25 0.09/0.30 0.09/0.35 0.09/0.40 0.09/0.45

Gritstone pillars

4.3

0.08/0.20 0.08/0.20 0.09/0.30 0.09/0.30 0.09/0.40 0.09/0.40

Stained glasses

4.3

0.18/0.10 0.06/0.10 0.04/0.15 0.03/0.15 0.02/0.20 0.02/0.20

Wooden chairs

1.5

0.05/0.20 0.08/0.24 0.10/0.28 0.12/0.32 0.12/0.36 0.12/0.40

Openings

0.9

0.97/0.10 0.97/0.10 0.98/0.10 0.98/0.10 0.99/0.10 0.99/0.10

Wooden stalls

0.8

0.15/0.20 0.15/0.24 0.18/0.28 0.20/0.32 0.20/0.36 0.20/0.40

Organ

0.7

0.14/0.20 0.14/0.25 0.14/0.30 0.14/0.35 0.16/0.40 0.16/0.45

Limestone Roodscreen

0.4

0.04/0.30 0.04/0.35 0.05/0.40 0.05/0.45 0.06/0.50 0.06/0.60

The initial adjustment of the model is based on the T 30 values, following an iterative process sothat the absorption coefficients of selected materials (mainly gritstone in this model) is carefullychanged until measured and simulated spatially averaged values of reverberation time differs by no
more than 5%, which is the minimum noticeable difference (JND) associated to this parameter (4).
Once this first requirement is matched, other acoustic parameters are used for a "point to point" and"frequency band by frequency band" comparison of measured and simulated values, both in absolutevalues and in terms of their corresponding JND. In this case, EDT, C50, C80, D50 , and T S results havebeen included in the comparison. The model of Ripon cathedral's nave is considered adjusted with
76.7% of the measured and simulated results (considering all frequency bands) obtained for eachsource-receiver combination differing by no more than 2 JND, as generally recommended in room
acoustic simulation (8), and with 91.2% of values differing by no more than 3 JND, which can beconsidered acceptable for these kind of buildings (6).

4. RESULTS AND DISCUSSION
Acoustic parameter values derived from the impulse responses registered on site evidence thedifferences between the acoustic environments of the nave and choir. Such difference is evidenced in
the results for the reverberation time parameters.
The spectral behaviour of the reverberation time is shown in Figure 4. It can be seen that the T 30
in the cathedral nave is higher than in the chancel at all frequencies bands. The T 30m (T 30 midfrequency averaged) obtained in the nave (SN) is 4.3 seconds, which is above typical recommended
values for a clear speech transmission, being nevertheless within the limits of the preferred values
suggested by several authors for organ music and Gregorian chant (11,12). The 2.7 s measured in the
chancel, both when the source is placed in the choir and at the presbytery, presumably denote a moresuitable acoustic environment for the variety of the requirements of the space in terms of sound.
However, caution needs to be exercised when referring to recommended values in relation tocathedrals as the perception of reverberation is strongly influenced by psychoacoustic and cultural
factors, and the objective values recommended for the perception of speech and music can be at odds
with visitors’ expectations. For example, Carvalho (13) published a comparison between two identicalchapels but with different acoustic treatments, and that paper pointed out that users preferred the more
reverberant chapel, objectively less suitable for the transmission of the word, because they were used
to the traditional reverberant acoustic environment of Portuguese churches.
The perceived reverberation is better assessed with the Early Decay Time parameter. EDT m
measured values, when frequency averaged, reveal that the perceived reverberation does not
significantly vary with the relative position of the listener, neither in the nave nor in the chancel. The
exceptions are those receivers located in the choir stalls when the sound source is placed in the choir(SC), whose EDT values are lower than in the rest of the choir, mainly due to their closeness to thesound source (S-R distances lower than 5 m). Results also pointed out that, when the source is placedin the nave (SN), the perceived reverberation in the transept is higher than in the nave (in Figure 4,
see the two points at about 17.6 m from the sound source, corresponding to R11 and R29 in Figure 1,
showing a EDT mid of almost 5 s). Obtaining EDT values higher than those obtained for T 30 in receiver
positions at that distance from the source is unusual, and may be due to some strong early reflections
presumably coming from the roodscreen.
In terms of sound clarity, in this particular paper we have focused on assessing music through C80,and speech intelligibility through the Speech Transmission Index, STI. Further analysis in relation toother parameters will be conducted in future studies. Figure 4 shows C 80 values, spectrally average,
and STI measured at each source-receiver combination. If the attention is focused on the values
obtained from the impulse responses measured in the chancel, both with the source located in the choir(SC) and in the presbytery (SA), it can be seen that measured values denote acceptable/good acoustic
conditions both for music (C80m > -5dB) and for speech transmission (STI > 0.45 except for thosepositions located furthest from the sound source, with a S-R distance > 15 m). Similar results are
obtained in the nave regarding clarity of music, although, in general, low values of C 80 parameter are
registered when the S-R distance is greater than 15 m. However, STI values rated as poor are measured
in all those receiver positions located more than 8.5 m apart from the sound source (SN), which meansa poor quality of the transmission of the word in large part of the audience area when no PA system is
used.

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5

5
SN
SA
SC

4
EDTm (s)T30 (s)

4

3

3

2

2

1

1
125

250

500

1000

2000

0

4000

5

10

15

20

6

Good Accept. Excellent

1.0

4
0.8

2
0

0.6

-2

STI

-6

SN
SA
SC

-8

0.2

-10
0

Poor

0.4

-4

5

10

15

20

Source - Receiver Distance (m)

25

Bad

C80m (dB)25

Source - Receiver Distance (m)Frequency (Hz)

0.0
0

5

10

15

20

25

Source - Receiver Distance (m)Figure 4 – Reverberation time measured values, spatially averaged, for each frequency octave band
(upper row, left); EDT values, spectrally averaged, (upper row, right), measured at each sourcereceiver combination; C 80 values, spectrally averaged (lower row, left) measured for each sourcereceiver combination; and STI (lower row, right) measured for each source-receiver combination.
4.1 Acoustic mapping of the nave
In addition to the initial acoustic analysis reported above, further analysis of the acoustics of thenave of Ripon cathedral was conducted using acoustic simulation techniques. The use of thesimulation models allows a greater level of detail by extending the acoustic analysis through the wholeaudience area (previously limited to the receiver points set during the measurements) and including
more source receiver positions which were not included in the measurements mainly due to access ortime limitations.
The cathedral nave is where major celebrations and cultural events are normally held. There are 4
positions where the sound source is commonly placed for those events (See Figure 1). Speech-based
events use the pulpit (SNP ) and the nave altar (SNN ) as part of the daily service, nowadays, using anelectroacoustic support system to be able to reach the audience seated in the chairs furthest from thealtar. Behind the altar there are choir stalls (SNC ) in which the choir members are located whenaccompanying the service and the musicians are placed during the concerts held in the nave. Moreover,
the transept (SN T) is time to time used for small meetings and talks. All the furniture (with the
exception of the pulpit) is removable to be able to adapt the configuration of the altar space to thedifferent activities held in this part of the cathedral. In addition, the 15th century stone pulpit locatedin the south transept, next to the rood screen, has been included as another sound source position(SN OP) since apparently has been exceptionally used for sermons.
Mappings were generated by using TUCT, with the suggested number of rays (99000 rays) andsuggested echogram length based on T30 values. Map step was set as default (1 m) and the map height
was set to get 1.20 m from the floor. Figure 5 shows the acoustic maps of C 80 parameter at 1 kHz,

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x

x

SNA

SNC

Figure 5– C 80, 1kHz acoustic maps of Ripon cathedral nave with the sound source located in thealtar nave, SN A (left) and in the choir stalls, SNC (rigth).
obtained from the acoustic simulation. SN A and SNC have been considered in this case, as
representative sound source positions from where the music involved in liturgical and/or culturalactivities held in the nave is mainly performed. It can be seen how acceptable values of C 80 are reachedin the areas of the central nave and in the lateral aisles where audience/congregation is commonly
located during major celebrations and concerts.
Figure 7 shows the acoustic mappings of the STI generated to assess the perception of speech inthis part of the cathedral. Same conditions were used for all the STI estimations: Background noise
NCB28, emission level of the sound source 94 dB SPL 1 KHz. Regarding the nave, it can be seen that
only in the altar space and in the closer positions in the chairs of the central nave, both for SN P and
SN A, values of STI rated as fair/good are reached. These results support the need to use anelectroacoustic support system to achieve a clear transmission of the speech even in the positions
furthest from the source, and especially if the background noise is higher. The use of electroacoustic
support is less critical when the activity takes place on the transept, as long as theaudience/congregation is not placed too far from the sound source position, limiting the audience area
to the central part of the transept for SN T, and avoiding the south transept when SN OP is used.

xSNP

SNA

x

SNOP

x

xSN

T

Figure 7 – STI acoustic maps of Ripon cathedral’s nave and transept with the sound source locatedin the nave altar, SN A (upper row, left); in the pulpit, SN P (upper row, right); behind the choir stallsof the nave, SN T (lower row, left), and in the old pulpit, SN OP (lower row, right).

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5. CONCLUSIONSThis paper summarised an initial acoustic analysis of Ripon cathedral performed as part of theMarie Skłodowska-Curie project Cathedral Acoustics. The aim of this work was to analyse theacoustic field of the space, evaluating it in terms of the perceived clarity of sound, both for music andspeech transmission, attending to the great variety of uses and spatial configurations that this complex
building allows.
It is not the purpose of the paper to judge how users experience the acoustic environment of thecathedral, but the influence the building has on the quality of sound depending on the use and theconfiguration of the space. The first peculiarity of this cathedral, is that the physical separation
between the nave and the chancel, makes them behave like two acoustically semi-independent spaces,with different reverberation times (4.3 and 2.7 respectively). In view of the results of themeasurements and the simulations, the nave is a magnificent place for music performances, althoughapparently it is too reverberant for a good transmission of speech without the use of any
electroacoustic support (STI rated as poor for the majority of the audience area).
A less reverberant acoustic environment, more suitable for speech transmission and nonecclesiastical music performances, is apparently experienced in the chancel, where acceptable valuesof C 80 and STI are reached in the majority receivers included in the study.
A more in-depth acoustical analysis through the acoustic measurements and also through theacoustic simulation will be conducted.

ACKNOWLEDGEMENTS
This work is part of the project Cathedral Acoustics, which is funded through the European Union’s
Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement
No. 797586. The authors are very grateful to the Dean and the staff of the cathedral for theircollaboration and their assistance during the measurements. Thanks to Oliver Caroe for kindly sharing
the digital CAD survey drawing data on the Cathedral. Thanks to Richard A. Carter for his kind help
during the acoustic measurements and for the photographs taken.

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