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

Physical measurements vs. auditory assessment of a concert hall bydifferent groups of users: a case study
Tadeusz FIDECKI1; Jan ŻERA2; Andrzej MIŚKIEWICZ3; Barbara OKOŃ-MAKOWSKA3;
Tomira ROGALA3; Teresa ROŚCISZEWSKA3; Ewa WIĘCKOWSKA-KOSMALA4;
Maciej JASIŃSKI2; Maciej ŁUKASZEWICZ5
1
2

Audiovid FF, Dembowskiego 3/10, 02-784 Warsaw, Poland

Warsaw University of Technology, Faculty of Electronics and Information Technology, Institute ofRadioelectronics and Multimedia Technology, Nowowiejska 15/19, 00-665 Warsaw, Poland

3

The Fryderyk Chopin University of Music, Department of Sound Engineering, Okólnik 2, 00-368 Warsaw, Poland
4

ewkAkustika Ltd., Anny Jagiellonki 4, 01-989 Warsaw, Poland

5

Manufaktura Technologiczna Ltd., Puławska 38, 05-500 Piaseczno, Poland

ABSTRACTThe acoustical quality of a medium size (6200 m3 volume, 880 seats) shoebox shaped symphonic concert hall,renowned for its acoustics and protected by the cultural heritage law, was evaluated by the measurement of
acoustic parameters (EN-ISO 3382-1:2009) and by auditory assessment of sound with the use of survey
questionnaires which required from the respondents to judge various attributes of sound and comment on
their experience with the hall. The judgments were obtained from the conductor, the soloists, orchestra
members, choir singers, recording engineers, and from the audience. The hall’s acoustics received generallyhigh ratings from the audience. Orchestral musicians highly estimated the audibility of one’s own instrument
and other instruments in the orchestra. Choir singers judged the audibility of other voices in the choir assatisfactory. The conductor assessed the overall sound quality as good, but also pointed at insufficient fusionof sound across the orchestral instrumental groups. Sound engineers judged the hall’s acoustics as very goodfor recording of chamber music and small orchestras, but not for very large ensembles. An attempt is made inthis paper to relate the results of auditory judgments of the hall’s acoustics to its measured acoustic parameters.
Keywords: Room acoustics, Subjective assessment, Sound quality

1. INTRODUCTION
The building of the Ignacy Jan Paderewski Pomeranian Philharmonic in Bydgoszcz, Poland, waserected in 1950s and the orchestra began regular activity in the new venue in 1958. The concert hall of
the Philharmonic is considered an exemplar of superior acoustics for symphonic music, chambermusic and solo recitals, as well as for sound recording. Currently the philharmonic building needs
comprehensive modernization after over 60 years of use. To keep a detailed documentation of theconcert hall’s acoustics for the future a comprehensive study was undertaken, including acoustic
measurements, auditory sound quality assessment, and a survey questionnaire on the hall’s acoustics
conducted among musicians and recording engineers. The study also included an acoustical inventory
and numerical modeling of the hall and documentary recording of symphony concerts. The purpose of
the study was to create detailed, comprehensive documentation of the hall that would help in therenovation and serve as reference for the evaluation of the results of the renovation project. This paper
presents the results of the study and discusses the relation of auditory judgments of the hall’s acoustics
to the measured room acoustic parameters.
1

tadeusz.fidecki@gmail.com
j.zera@ire.pw.edu.pl3
andrzej.miskiewicz@chopin.edu.pl
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2. GENERAL CHARACTERISTICS OF THE CONCERT HALL
The building of the Ignacy Jan Paderewski Pomeranian Philharmonic houses a symphonic concert
hall (6200 m3 volume) and a chamber hall (890 m3 volume). The concert hall is situated above thechamber hall in the building . A side view and a floorplan of the concert hall are shown in Figure 1.

Figure 1 – A cross-section, a floorplan, and a scan image of the Pomeranian Philharmonic concert hall
The main specifications of the concert hall are as follows: capacity: 886 seats, volume: 6200 m3,
volume per seat: 7 m3, floor area: 675 m2 , stage area: 163 m2, hall length: 36 m, width: 21 m, maximum
height: 12 m. The hall has a shoebox shape with the exception of a sloped floor in the audience area.
The ceiling is tilted above the stage and lowered to about 7 m in the rear to reflect sound to theaudience and provide good acoustic conditions for communication between musicians on the stage.
2.1 Materials
The hall’s iterior (walls) is entirely covered with wood. The wall covering is made of deeply
profiled wood panels (Figure 2, bottom part), wave-shaped profiled wood boards (Figure 2, wall on theleft), and flat perforated panels.

Figure 2 – A cross-section of profiled wood panels and wave-shaped panels covering the bottom part of thehall’s side walls
Profiled panels, arranged at a distance of 35 mm from the layer of bricks, cover the lower parts ofthe side walls in the audience area and the bottom part of the back wall. The higher parts of the sidewalls are covered with flat panels. On the back wall, flat panels alternate with flat perforated panels
arranged at a distance of 105 mm from the brick layer, some slightly tilted. The profiled wood panels(Figure 2, bottom) provide side-wall scattering of high-frequency sound in the audience area.
Wave-shaped board panels (Figure 2, left) are predominant on the stage side walls. An important partof the stage back wall is the organ prospect strongly dumping the sound at mid frequencies (1 kHz).

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Other acoustic elements include: (1) a reflecting ceiling covered with a 20-mm gypsum face set on
a net attached to 20-mm slabs above the stage; (2) the ceiling above the audience area, 3 m wide,
shaped in shallow contra tooth like surfaces, (3) wooden floor laid on a 50-mm concrete layer; (4)armrest chairs with medium thickness cushions in the seating area. An almost entirely wooden
coverage of the interior surfaces results in relatively short reverberation time at 63- and 125-Hz
frequencies and provides even sound decay throughout the audience area.

3. ACOUSTIC MEASUREMENTS AND NUMERICAL SIMULATIONS
3.1 Measurement setup and procedure
Most of the acoustic measurements were carried out in compliance with the EN-ISO 3382-1
standard [1] and consisted in recording of impulse responses from which the basic parameters andindexes were calculated. In addition to that, the Interaural Cross Correlation, IACC, was also assessed.
The measurement setup included a Brüel & Kjaer 4292-L dodecahedron loudspeaker, a RME Fireface
UC interface, two Microtech Gefell MK250 condenser microphones, a Dell XPS M1330 notebook
with DIRAC Room Acoustic Software 7841, and a Brüel & Kjaer 2250 sound level meter. IACC was
calculated from binaural recordings made with a Neumann KU100 dummy head.
The measurements were conducted both in an empty hall and during concerts, with 50 orchestra
musicians and either 50 or over 80 choir singers on the stage, and fully occupied audience area. The
measurements in an occupied hall were performed just before the concert with the consent of the
conductor, the musicians, and the audience. The Brüel & Kjaer 4292-L sound source was placed among
the musicians, close to the median of the stage, at a distance of about 1.5 m from the edge of the stage,
approximately at the place intended for a concert soloist. The two measurement microphones wereplaced in two locations on the stage, among musicians, and moved from one place to another along theleft and right aisles (see Figure 1) in the audience area. Eight placements in the audience area wereused, with gradually increasing four distances from the stage, ranging from 1.5 m in the first seat row to
19.5 m in the 21st row. In an unoccupied hall 2–7 sound source placements were used, depending on
the parameter measured. For IACC recordings the dummy head was placed in 10 locations, five along
the room median axis and five on the right side of the hall.
3.2 Results
The main results of the measurements are shown in Figure 3 and Tables 1 and 2. It is apparent in
Figure 3ab that the frequency characteristics of reverberation time, RT, and early decay time, EDT,
have a bow-like shape with a maximum in a range of 500–1000 Hz. The average RT, measured in theaudience area, is 2.1 s in an empty hall and 1.8 s in an occupied hall (Table 1) and the respective EDT
values are 1.9 and 1.5 s. These data indicate that the room reverberation decreases by about 15%
during concerts in a fully occupied hall. The difference in reverberation time between an empty and an
occupied hall is not larger than typically encountered in concert halls but is still audible, as it exceeds
the auditory discrimination threshold for reverberation time [2]. It also should be noted that the RT andEDT values are similar across the measurement points in the hall. The average sound strengthparameter, G (Figure 3c, Table 2) is about 4 dB, except for an increase to 9 dB at 125 Hz. This increasein sound strength provides good bass support in the hall. In general, all basic acoustic parameters arewithin a range recommended for a concert hall of such a size: T30=1.7 ÷ 2.2 s, EDT = 1.4 ÷ 2.0 s, C 80=–3 ÷ +3 dB, C 50 = –1 ÷ +3 dB. The stage support parameters, ST Early and ST Late (Table 2), indicate goodacoustical conditions for communication between musicians on the stage and for communication
between the conductor and musicians.
Initial time delay gap, ITGD, shown in Figure 3d, was measured for six microphone distances fromthe stage in the audience area and seven placements of the sound source on the stage, covering theentire stage depth in 1.5 m steps. As expected, the largest ITDG values of 40 ms were obtained at ashort distance with the sound source located close to the stage edge and the microphone placed in thefirst seat row (1.5 m from the stage) and the fifth row (4.5 m from the stage). The ITDG decreased to
10 ms either with sound source moved to the rear of the stage or the microphone placed at the end of
the audience area (row 23). The ITDG, averaged over the microphone placements in the audience area,
decreased from 27 to 12 ms when the sound source was moved from the front to the rear of the stage.
IACC (Table 2) indicates good sound quality in the hall as the average initial IACC 0-80 is about 0.4
and late IACC 80+ is below 0.2. The listener envelopment parameter, LEV, is 1.4 dB and the degree ofsource broadening parameter, DSB, is 27 dB. These values indicate good spatial perception in the hall.

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a)

b)

c)

d)

Figure 3 – a) Reverberation time T30, b) EDT on the stage and in the audience area in an occupied and in an
empty hall, c) sound strength G80 in the middle and in the side (close to the side wall), d) ITDG determinedfor various placements of the sound source on the stage and various distances of the microphone in theaudience area
Table 1 – Reverberation time (T30), early decay time (EDT), clarity (C80), speech clarity (C50)
Average
Stage

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Audience area

Front-back change

Numerical

Audience area

model

Parameter

Unoccup.

Occup.

Unoccup.

Occup.

Unoccup.

Occup.

T30, s

2.1

1.7

2.1

1.8

2.0 ÷ 2.1

1.7 ÷ 1.8

1.9

EDT, s

2.2

1.5

1.9

1.5

2.2 ÷ 1.8

1.7 ÷ 1.4

1.8

C80, dB

7.3

−

0.2

−

1.5 ÷ -1.5

1.5 ÷ -0.6

–0.8

C50, dB

3.0

5.5

–2.8

–2.6

-0.8 ÷ –4–1.2 ÷ –4.8

–4.3

STI

0.62

0.74

0.51

0.53

−

−

0.49

Table 2 – IACC0-80 (Early) and IACC80+ (Late), sound strength G, and stage support ST
Average

Front-back change in audience

Numerical

area
Parameter

MiddleSide

Middle

Side

model

IACC0-80, ms

0.50

0.33

0.70 ÷ 0.36

0.42 ÷ 0.26−

IACC80+, ms

0.18

0.12

0.20 ÷ 0.15

0.12 ÷ 0.11−

Gtotal, dB

7.5

6.5

8÷6

8÷6

8.7

G0-80, dB

4.4

3.2

6÷2

6÷1

−

G80+, dB

5.5

3.8

7÷3

5÷3

−

STEarly, dB

–12.9

−

−

STLate, dB

–14.3

−

−

3.3 Numerical simulations
A numerical model of the hall was created, based on laser scanning of the hall interior (Leica P20
scanner, tachimeter TS09 R1000). The raw data were exported to a CAD environment to create acomputer model consisting of 795 planes subdivided into 16 groups with assigned absorption
coefficients. The modeling was done with the use of AURA/EASE 4.4 software.
In the model’s development a difficulty arose due to the lack of sufficient data on the absorption
coefficients of certain surfaces in the hall. There was no proper documentation from the time when thehall was being built and the various wood panels were differently and deeply profiled (see Figure 3c),and differently separated from the brick walls. This prevented the use of catalogue absorption
coefficient values in the model so it was decided to perform in situ measurements of absorption
coefficients with the use of a Microflown Technologies sound absorption probe. Sound absorption
coefficient, α, was measured for all surfaces included in the numerical model, i.e., the profiled wood
panels on the stage and on the audience area side walls, perforated and unperforated panels in theupper parts of the walls, the ceiling above the stage and the audience area, the floors, chairs, doors, andthe organ prospect. The measurements were made at a given point or – in the case of profiled wood
panels and the organ prospect – by scanning the surface during an assumed averaging time (15 s).
The sound absorption probe tends to overestimate the absorption coefficient if the probe is notplaced close enough to the measured surface, which made the measurements of profiled panels
difficult. A comparison of measured parameters (Table 1 and 2) and the outcome from the numericalmodel showed that the results of in situ measurement of sound absorption were overestimated by about
25%. Thus, the final modeling was performed with all absorption coefficients reduced to 80% of theirmeasured values. Reduction of the coefficients also depended on the frequency band and ranged from0.69 to 1.00, respectively, at 125 and 4000 Hz.
As an output of numerical modeling reverberation time T 30, EDT, clarity C 50 and C 80 indexes, STI,
and sound strength G were calculated. These data are shown in Figure 3 and in Tables 1 and 2. Overall,it should be noted that the in situ measurement of sound absorption resulted in good agreement of thesimulations with the measurements of room acoustic parameters.

4. AUDITORY ASSESSMENT
4.1 Questionnaires of orchestra and choir members
Subjective assessment of various aspects of the concert hall sound quality included questionnaires
given to orchestra and choir members and interviews conducted with choir and orchestra conductors,
soloists and sound engineers who had experience in music recording in the hall. The questionnaires
were intended to collect opinions regarding the audibility and quality of sound during rehearsals andconcerts and the comfort of performing music in the hall. Separate question categories were preparedin the questionnaires for orchestra and choir members, due to the specificity of their work.
The questionnaire survey was conducted during two concerts among 51 orchestra members and 58
choir members (concert 1), and 50 orchestra members and 82 choir members (concert 2). In total, 2413955

questionnaire forms were collected from the musicians. During those concerts acoustic measurementsof the hall, described in section 3, were also conducted.
The questionnaire for orchestra members included questions concerned with various aspects of
their work on the stage and general questions about the hall. Two questions given to orchestra members
were about the sound of their own instrument: (1) audibility of the sound and (2) sound clarity. Further
questions were about (3) the audibility of instruments of own section and (4) audibility and (5) clarityof other instrumental sections. There also was a question about (6) the sound projection range of the
respondent’s instrument and (7) the intelligibility of the conductor’s voice.
The choir members were questioned about the sound of their own voice, its (1) audibility, (2) clarity,and (3) ease of voice emission. The remaining questions were about (4) audibility of other choirmembers from the same section and (5) audibility of other choir sections, (6) fusion of the choir sound,(7) audibility of the orchestra and (8) intelligibility of the conductor’s voice.
The surveyed musicians responded by selecting one of three rating categories: poor, average, andgood. Table 3 presents the percentage of responses assigned to each of the categories and a numericalindex representing a weighted average, with weights of ‘0’ for poor, ‘0.5’ for average, and ‘1’ for good
category. The index shows the group result of rating on a scale from 0 to 1; an index value greater than
0.5 means that a given aspect of sound was positively evaluated by the respondent s.
The questions about the hall quality were about (1) comfort of ensemble playing in the orchestra or
comfort of singing with the orchestra (2) overall sound quality on the stage, (3) overall sound quality
in the concert hall. In this group of questions a five-category rating scale was used, extending fromvery bad to very good. Table 4 presents the percentage of responses assigned to each category. Similarly
as in Table 3, an index representing the weighted average was calculated, with weights ‘0’ for ‘very
bad’ and ‘1’ for ‘very good’. The index represents the average rating on a scale ranging from 0 to 1.
Table 3 – Percent distribution across rating categories obtained from orchestra members and choir membersin the evaluation of sound in the concert hall. Rating categories: poor, satisfactory, good.
Orchestra members
Response
category

Choir members

Poor

Satisf.

Good

Index*

%

%

%

0÷1

Sound of the respondent’s own instrument

Response
category

Poor

Satisf.

Good

Index

%

%

%

0÷1

Sound of the respondent’s own voice

Audibility

3

25

72

.84

Audibility

2

29

69

.84

Clarity

5

22

73

.85

Clarity

3

29

68

.82

Ease of voice
emission

3

28

69

.84

Sounds of other instruments in the orchestra

Voices of other choir members

Audibility of-own section

6

56

38

.66

Audibility of-own group

9

48

43

.67

-othersections

6

52

42

.68

-other voicegroups

23

55

22

.49

Clarity other sections

7

61

32

.63

Choir soundfusion

9

52

39

.65

4

43

53

.75

Audibility ofthe orchestra

0

26

72

.87

.64

Intelligibilityof
conductor’s
voice

3

54

43

.70

Other
Sound
projection
rangeIntelligibilityof
conductor’s
voice
*

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6

60

34

An index ranging from 0 (poor) to 1 (good), summarizing the responses, was calculated as a weighted average of ratings.

Table 4 – Percent distribution across rating categories obtained from orchestra members and choir memberson the following scales: comfort of playing, quality of sound on the stage and overall concert hall quality.
Response categoryVerybad (1)

(2)

(3)

(4)

Very
good(5)

Index*

%

%

%

%

%

0÷1

Comfort of ensemble playing
Orchestra

1

6

15

46

32

0.76

Choir

-

1

9

49

41

0.83

All

-

3

11

48

38

0.80

Stage sound quality
Orchestra

-

-

8

27

65

0.89

Choir

-

-

5

49

46

0.85

All

-

-

6

41

53

0.87

Hall sound quality
Orchestra

-

1

7

28

64

0.88

Choir

-

1

6

50

43

0.84

All

-

1

7

41

51

0.86

*An index ranging from 0 (very bad) to 1 (very good), providing a summaryof responses, was calculated as weighted average of ratings

The results compiled in Table 3 show that musicians generally approved the acoustics of the concert
hall. Almost 75% of orchestra members rated the audibility and clarity of own instrument as “good”.
Audibility of instruments in the own and in other sections, as well as the clarity of sound of other
instrument sections were judged as satisfactory or good. The corresponding weighted average index
values were high: 0.69 for the sound of own instrument and 0.6÷0.7 for other instruments. The
musicians were also satisfied with the sound projection range (index = 0.75) but less so with theintelligibility of conductor’s voice, judged as only satisfactory. This result is in good agreement withthe measured values of STI index on stage: 0.62 in an empty and 0.74 in an occupied hall.
The responses of choir members were similar to those of orchestra members and indicated highacceptance of the quality of own voice, neighboring singers’ voices, and the overall sound of the choir(category ‘choir sound fusion’). The lowest rating was given to the audibility of other voice groups inthe choir (index = 0.49), but still at a satisfactory level. It should be noted, that the evaluated concert
hall was the home hall of the orchestra therefore the musicians were very well familiar with its
acoustics. Both choirs performed as guest ensembles in the hall and had much less experience with thehall’s acoustics.
All musicians positively assessed the comfort of playing in the hall, and quality of sound on thestage as well as sound in the hall as a whole. The data in Table 4 show that over 90% of ratings of stage
and hall sound quality fall into categories (4) and (5), labeled ‘very good’. The comfort of ensemble
playing was rated (4) and (5) in 78% cases, which is slightly less, but still very good. This could be
related to relatively small stage area of this hall to accommodate over 130 musicians .
4.2 Comments of conductors, a soloist, and sound engineers
Comments were obtained from three orchestra conductors, two choir conductors and a soloist ( awoman who sung in Mozart’s Requiem). All those persons generally highly valued the hall, yet they
had specific remarks regarding some deficiencies. The stage was judged as providing good soundquality at the place occupied by the conductor, however, with some complains about the lack ofsufficient fusion of instrument sounds, especially in very large ensembles for which the hall issomewhat too small. A good feature of the acoustics in the stage area is easy communication of the
conductor with the soloist and orchestral musicians. The hall provides good sound balance between theorchestra and the choir. However, some instrumental groups do not hear each other well enough which3957

makes it difficult to synchronize the sounds of the instruments and this also applies to remotely locatedsingers in large choirs. The hall is demanding for a solo singer who must, to a large extent, rely on
his/her singing technique and receives moderate acoustical support from the room. The choir is well
supported by the hall’s acoustics when the ensemble is not too large and fits in the area close to thecenter of the stage.
Regardless of certain performance difficulties, the sound is precise in the concert hall. On the other
hand, it is not easy to play in the hall as it does not mask performance imperfections. The timbre ofreverberant sound is correct. An important feature of the hall is that the difference between the
acoustics of an empty and a filled hall is very small. Regardless of the detailed, somewhat criticizing
comments, the overall sound quality was judged high and comparable to major concert halls in Europe.
Comments were also gathered from 11 sound engineers who used to work in the concert hall, atpresent or in the past. They emphasized that the hall is very well suited to the needs of music recording.
For instance, the hall acoustics allows to use omnidirectional microphones placed at large distancesfrom the sound source and microphone placement is easy in the hall. The hall is best for chamber andother relatively small ensembles and also very good for recording of works for piano and an orchestra.
The intimacy of the hall’s sound is audible in the recordings. The hall has a good ratio of direct toreverberated sound and the reverberation time is proper for music recording. Despite of several
specific critical remarks, the hall is unique in many aspects and very friendly for music recording.

5. FINAL REMARKS
Measurements done in the Pomeranian Philharmonic concert hall showed that it was possible toexpect good acoustical conditions of the hall. Basic parameters such as reverberation time T 30, EDT,
clarity C 50/80, stage support ST and strength G assumed values correct for music performances in thehall of this volume. Binaural parameters (IACC and derived from it LEV and DSB) also predicted
good hall quality. Results of measurements were at large confirmed by subjective quality assessment
done by performers, conductors, sound engineers, and persons from the audience.

ACKNOWLEDGEMENTS
The second author’s participation in the ICA 2019 congress was supported by the statutory grant504/04064/1034/40.00 from the Warsaw University of Technology.

REFERENCES
1. EN ISO 3382-1: 2009. Acoustics – Measurement of room acoustic parameters – Part 1: Performance
spaces.
2. Vorländer M., Auralization, Fundamentals of Acoustics, Modelling, Simulation, Algorithms and Acoustic
Virtual Reality, Springer 2008.

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