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

Correlations between sound level and loudness, intimacy,reverberation, clarity, spaciousness in sequential spaces
Tingting YANG1; Jian KANG2
12Institute for Environmental Design and Engineering, The Bartlett, University College London,London WC1H 0NN, United Kingdom

ABSTRACTTo explore the acoustic environment of sequential spaces, the paper discusses the correlations between
sound level and five independent dimensions of acoustic environment including loudness, intimacy,
reverberation, clarity and spaciousness. Two sequential spaces with similar spatial composition wereselected for questionnaire survey and field measurement. The results showed that under the conditionof no sound source, sound level only affected loudness. Under the condition of sound source, a higher
sound level resulted in a higher loudness, reverberation and spaciousness. Sound level differences
between the rooms did not necessarily correspond to assessment difference in these three indicators.
Intimacy was negatively correlated to clarity, and there was a threshold of sound level difference
related to assessment difference of these two indicators.
Keywords: Sequential Spaces, Sound Level, Subjective Evaluation

1. INTRODUCTION
Sequential spaces, defined as a series of spaces connected by openings, is a spatial form widely
applied in designing non-acoustic spaces such as museums and commercials since 16th century andeven earlier. Thus, acoustic perception of such spaces is important for indoor soundscape.
Listeners’ responses have always been the focus of room acoustics. Researches on acoustic space
are fruitful in this area. Previous studies proposed that there are at least five independent dimensions:clarity, reverberant response, impression of space, intimacy and loudness (1). Barron (2) mentionedthat these five dimensions are not complete or definitive but they have provided a useful starting point
for further discussion. Ando also showed that a concert hall has four subjective dimensions: loudness,reverberance, clarity and spaciousness (3).
Although loudness may not be the most appreciable indicator for designing a concert hall, theimportance of acoustic perception is self-evident. The sense of loudness is predictably related to soundlevel and judgements overlap between intimacy and loudness (2). Hase et al. conducted an experimenton subjective reverberation in a concert hall with sound level of 70 and 80 dB, respectively, using bothspeech and music signals. The sense of reverberation of 80 dB was stronger than that of 70 dB when allother conditions were the same. Therefore, sound level is also considered to affect the reverberation(4). Furthermore, either a too high or low sound level will decrease clarity, which will also affectintelligibility. In the aspect of spaciousness, previous studies mentioned that when the mean fortesound level reaches 90 dB, there will be a satisfied sense of space (5).
Based on these studies, it can be concluded that sound level is an important objective parameter toevaluate the acoustic environment of a space, and there are close correlation s between sound level andthese five dimensions. However, these studies are developed on the researches of single space, which
could be inadequate to analyse the sound field in non-acoustic sequential spaces (6, 7). Thus, the paper
selected two sequential spaces, which are similar in spatial conditions, to explore the correlation
between sound level and five independent dimensions of loudness, intimacy, reverberation, clarity,and spaciousness in sequential spaces.

124158tingting.yang.18@ucl.ac.uk
j.kang@ucl.ac.uk

2. METHODOLOGIES
2.1 Site Selection
The selection of site was primarily based on the consideration of spatial conditions to meet therequirements of subjective evaluation and objective measurement. The paper selected a gallery in
London for investigation, in which most of exhibition spaces are sequential spaces of different scales
exhibiting modern arts all the year round. This gallery is an enjoyable place for locals and tourists withcomparatively high visiting amounts.
Two sequential spaces which are connected by the concourse on the right and left side were selected
for the conditions of sound source. Figure 1 shows the floor plan of these two sequential spaces,
concourse and the location of sound source. The sound source is a large sound installment formed as acylindrical tower with hundreds of radios playing vocals, and music that are virtually unintelligible.
Figure 2 shows a typical exhibition room. The basic conditions of spatial composition and couplingareas as well as design of the interior, exhibition environment, and peak hours of these two sequential
spaces are essentially the same. Therefore, for the comparative study, the sequential spaces on the rightside of the concourse in Figure 1 was defined as sound-source-group, and the sequential spaces on theleft side of the concourse was defined as no-sound-source-group.

Figure 1 – Floor plan of two sequential spaces, concourse and the location of sound source

Figure 2 – Site photo a typical exhibition room
2.2 Questionnaire Survey and Field Measurement
To explore the correlation between sound level and five dimensions, a questionnaire survey onsubjective evaluation was carried out. The questionnaire consisted of questions on person factors (ageand sex) and assessments of loudness, intimacy, reverberation, clarity, and spaciousness. The
respondents were instructed to answer on a five-point unipolar category scale using the following
response alternatives: (1) “not at all”, (2) “slightly”, (3) “moderately”, (4) “very”, and (5) “extremely”.
The subjects were randomly recruited among the visitors in the concourse who completed their visit
to the exhibition space on Level 4. The experiment employed soundwalking and the subjects walked
individually through the prescribed route and rated the subjective evaluati on of each marked room
while standing in the center of each space. All subjects in the no -sound-source-group took thedirection from rooms 5 to 8, while the subjects in the sound-source-group were further subdivided into
two smaller groups. The subjects who took the direction from rooms 4 to 1 were defined as
towards-sound-source-group, and the subjects who took the direction from rooms 1 to 4 were definedas away-sound-source-group. A total of 36 subjects in each group were surveyed based on the criterionof normal distribution number that the sample size should be larger than 30. Each 108 subjects
completed the questionnaire for four rooms, which amounted to 432 valid questionnaires.

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To measure the mean value of sound level of each room, HEAD Acoustic SQobold was used tocapture a one minute long recording of the environment close to the place where the subjects filled in
the questionnaire representing the physical characteristics of the occupied condition. Themeasurements of sound level were averaged as the results.

3. RESULTS
3.1 Measured Sound Level
Table 1 shows mean values and variances of sound level in each room of no-sound-source-groupand sound-source-group through the measurements during the data collection. For theno-sound-source-group, the highest mean value was 59.1 dBA in room 5, while that in rooms 6, 7 and
8 were basically equivalent. Statistical significance between rooms 5 and 6 was great (mean value
difference = 2.2 dBA, p < 0.01). For the sound-source-group, the highest mean value was 68.3 dBA inroom 1, while that in rooms 1 to 4 showed a descending tendency. There was statistical significancebetween rooms 1 and 2 (mean value difference = 5.7 dBA, p < 0.01) as well as between rooms 2 and 3(mean value difference = 3.8 dBA, p < 0.01).
Table 1 – Mean values and variances of sound level of sound-source-group and no-sound-source-groupSound-source-group
LAeq

No-sound-source-group

Room 1Room 2

Room 3

Room 4

Room 5

Room 6

Room 7

Room 868.3±2.41

62.6±2.80

58.8±2.95

59.7±3.37

59.1±4.66

56.9±4.81

55.3±5.49

53.8±5.71

3.2 Correlation between Sound Level and Five Dimensions
Based on the results of sound level in section 3.1, the correlations between sound level and fivedimensions were analysed with no-sound-source-group and towards-sound-source-group dependingon the mean values and their difference among the rooms.
For the no-sound-source-group, loudness and spaciousness were different between each room (p <0.05). Table 2 reveals mean value and variance of loudness and spaciousness in each room. In terms ofloudness, the highest mean value was rated at 2.5 in room 5, and that in rooms 6, 7 and 8 were basicallyequivalent. There was statistical significance between rooms 5 and 6 (mean value difference = 0.5, p <0.01). In terms of spaciousness, the lowest mean value was rated at 2.6 in room 6, and that in rooms 5,
7 and 8 were basically equivalent. Statistical differences between rooms 5 and 6 (mean valuedifference = 0.6, p < 0.01) and rooms 6 and 7 were great (mean value difference = 0.6, p < 0.01).
Table 2 – Mean values and variances of loudness and spaciousness of no-sound-source-group
Room 5

Room 6

Room 7

Room 8

Loudness

2.5±0.81

2.0±0.77

2.0±1.07

2.0±0.83

Spaciousness

3.2±0.95

2.6±0.96

3.2±0.93

3.1±0.95

Loudness was closely related to sound level, and 2.2 dBA difference resulted in different perceived
loudness in sequential spaces. On the other hand, spaciousness showed a wide disparity with soundlevel. Thus, under the condition of no sound source, spaciousness is not directly related to sound levelin sequential spaces.
For the towards-sound-source-group, all five indicators showed statistical significance (p < 0.05).
Table 3 gives mean values and variances of all five indicators in each room. In terms of loudness, thehighest mean value was rated at 3.9 and it showed an ascending tendency from rooms 4 to 1. The
difference between rooms 1 and 2 (mean value difference = 0.9, p < 0.01) as well as rooms 2 and 3 wasvery statistically significant (mean value difference = 0.6, p < 0.01). In terms of intimacy, the highest
mean value was rated at 3.0 in room 1. Statistical significance was shown in rooms 2 and 1 (mean valuedifference = 0.5, p < 0.05). In terms of reverberation, the highest mean value was rated at 3.2 and thedifference between rooms 2 and 3 was great (mean value difference = 0.5, p < 0.01). In terms of clarity,
the highest mean value was rated at 3.2 and there was statistical significance between rooms 2 and 1(mean value difference = 0.7, p < 0.01). In terms of spaciousness, the highest mean value was rated at
3.4 and the difference between rooms 2 and 3 was great (mean value difference = 0.6, p < 0.01).
Table 3 – Mean values and variances of loudness, intimacy, reverberation, clarity and spaciousness of4160

towards-sound-source-group
Room 1Room 2

Room 3

Room 4

Loudness

3.9±0.57 3.3±0.59

2.4±0.73

2.2±0.64

Intimacy

3.0±1.23 2.5±0.88

2.5±1.08

2.1±1.08

Reverberation

3.2±1.18 3.0±0.84

2.5±0.91

2.6±0.77

Clarity2.5±1.06 3.2±0.85

3.2±0.96

3.0±1.11

Spaciousness

3.4±1.25 3.1±0.82

2.7±0.68

2.9±0.95Note that assessment difference in loudness between rooms 2 and 3, which was paired with soundlevel difference 3.8 dBA, was larger than that of rooms 1 and 2, which were paired with sound level
difference 5.7 dBA. This indicates that sound level difference does not necessarily correspond toassessment difference in loudness. A positive correlation between sound level and loudness wasobserved, which shows consistency to the results of single space. Intimacy increased with sound levelas loudness in the room containing the sound source. However, this was not necessarily the case in theroom with no sound source. Similarly, the result of 0.7 assessment difference in clarity paired with 5.7
dBA but no difference under 3.8 dBA indicates that 4 dBA sound level difference may not result indifferent perceived clarity, while 6 dBA difference would do. Room with a higher sound level insequential space had a higher reverberation. However, similar to loudness, sound level difference did
not necessarily correspond to assessment difference on reverberation. It could be also concluded thatspaciousness is affected by the sound level as well under the condition of sound source and a higher
sound level resulted in a higher spaciousness in sequential spaces.

4. DISCUSSIONS
4.1 Categories of Correlation
As discussed in section 3.2, correlations of sound level and five dimensions could be divided into
two categories under the condition of sound source: first is loudness, reverberation and spaciousness.
Figure 3 shows the tendency from rooms 1 to 4. They are directly affected by sound level. Second is
intimacy and clarity. Figure 4 shows the tendency from rooms 1 to 4. Both of them show a peak insound source room and a plateau in the other rooms, which indicates a threshold of sound level andacoustic perception difference.
These results also indicate the correlation within the five dimensions in sequential spaces. Note thatspaciousness is not related to sound level under the condition of no sound source. Thus, it is suggested
that since designing a sound source in sequential spaces would be very likely to result in a sequenced
sound level throughout the rooms, a sequenced perception of spaciousness would be created as well.

Figure 3 –Mean value tendency from rooms 1 to 4 (sound level, loudness, reverberation andspaciousness)

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Figure 4 – Mean value tendency from rooms 1 to 4 (sound level, intimacy, clarity)
4.2 Difference of directions
To identify the effect of direction in subjective evaluation, a T-test comparison was furtherconducted in the away-sound-source-group. There was statistical significance between loudness andclarity (p < 0.05). Table 4 gives mean values and variances of these two indicators. In terms ofloudness, the highest mean value was rated at 3.1 in room 1 and the difference between rooms 1 and 2(mean value difference = 1.2, p < 0.01) as well as rooms 2 and 3 (mean value difference = 0.3, p < 0.05)
was statistically significant. In terms of clarity, the lowest mean value was rated at 2.4 in room 1. The
statistical significance between rooms 1 and 2 (mean value difference = -0.7, p < 0.01) was high.
Compared to the results of loudness and clarity in the towards -sound-source-group, it is observedthat sound level difference was corresponding to assessment difference in loudness in theaway-sound-source-group, while in the towards-sound-source-group, a larger sound level difference
resulted in a smaller difference in perceived loudness. The expectation of loudness in two directions
was more likely to be different. On the other hand, the difference in clarity in rooms 1 and 2 werebasically equivalent of these two groups and showed the same tendency throughout the rooms.
Table 4 – Mean values and variances of loudness and clarity of away-sound-source-group
Room 1Room 2

Room 3

Room 4

Loudness

3.1±0.55

1.9±0.75

1.6±0.56

1.7±0.72Clarity

2.4±0.94

3.1±1.09

3.4±1.16

3.2±1.17

5. CONCLUSIONSThe paper took subjective evaluation and objective parameter as the research object exploring thecorrelations between sound level and five independent dimensions of acoustic environment insequential spaces. Under the condition of no sound source, sound level only affected loudness. Under
the condition of sound source, the result showed that a higher sound level resulted in a higher loudness,reverberation and spaciousness. Sound level difference did not necessarily correspond to assessment
difference of these three indicators. Intimacy was negatively correlated to clarity, and there is athreshold of sound level difference related to acoustic perception of these two indicators.

ACKNOWLEDGEMENTS
The authors express gratitude to all participants who completed the questionnaire and to the Tate
Modern, London. The authors also express gratitude to Francesco Aletta, Tin Oberman and thecolleagues of UCL IEDE Acoustics Group for the supports. This research was also supported by theEuropean Research Council (ERC) Advanced Grant (No. 740696) on “Soundscape Indices” (SSID).

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