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

Restorative soundscapes and stress recovery in children
Shan SHU1; Hui MA2
1, 2

Tianjin University, China

ABSTRACTEmerging studies have shown that restorative soundscapes have the potential to facilitate adults’ stressrecovery. Little is known, though, about whether restorative soundscapes could reduce children’s stress.
Therefore, the present study tested and compared the effects of several potential restorative soundscapes onchildren’s stress using a physiological measure: electrodermal activity (EDA). During the experiment, 53
children aged 8-12 were exposed to different soundscapes (recovery period) after a stressful arithmetic task(stressor period), while children’s EDA variation was monitored throughout the whole period. The results
showed that children’s EDA levels decreased significantly after all the soundscape exposure. However, only
the fountain soundscape showed significant a better restorative effect compared with ambient noise. In
addition, EDA decreased faster at the beginning and tended to increase slightly at the end of the recovery
period. Moreover, significant interaction effects were found between soundscape and gender as well as timeand gender. Those results suggest that soundscapes do facilitate stress recovery on children to some extent
after a psychological stressor. However, different soundscapes showed varied restorative effects on boys andgirls. Therefore, future soundscape design in urban parks should take children gender difference into
consideration.
Keywords: Restorative effects, Children, EDA

1. INTRODUCTION
Numerous studies have documented the restorative effects of interacting with naturalenvironments(1). As an essential part of physical environments, some pleasant soundscapes were alsosuggested to contribute significantly to the restorative effects of the environment (2). Those restorative
benefits of soundscapes could be framed in terms of two prevailing theories of restorativeenvironments: attentional restoration theory (ART) and stress recovery theory (SRT). ART is
commonly referenced to identify and restore a cognitive mechanism (3), while SRT focuses primarilyon the effects of environmental stimuli on psychophysiological responses, suggesting that interactingwith nature could evoke positive responses indicative of stress reduction (4).
Based on the SRT theory, many studies over the past decades have provided evidence for this bydemonstrating a restoration in stress-relieving measures, including psychological and physiologicalindices, after exposure to natural environments (4–7). In addition to the visual stimuli of natural
settings, which was predominantly reported in previous studies, psychophysiological benefits fromsoundscape exposure were also frequently suggested in some evidence-based research recently. Manyof those research focused on the comparison of natural sounds and noise (8,9) or with sound andwithout sound (10,11), while some explored the restorative effects of one specific sound, such asmusic (12,13) and birdsong (14). Additionally, a physiological study investigated the restorative
effects of different soundscapes but it failed to a reveal significant difference between soundscapes(15). Similar results were indicated in another study exploring the physiological responses to 18
sound-clips(16). Therefore, there is still a lacking of research on which soundscape could facilitate
stress reduction for people and to what extent such a soundscape could provide restorativeness.
Moreover, different studies applied various measure method to assess stress recovery after soundscape
exposure, which led to mixed results. For example, Alvarsson (8) found no significant difference
between nature sound and environmental noise on the recovery of high frequency heart rate variability(HF HRV) while a significant increase in HF HRV was indicated after exposure to nature sound in
1
2

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shan.shu@outlook.com
mahui@tju.edu.com

Cassandra’s study (9). These diverging results were also found in other physiological measurements,
such as heart rate (16) and skin conductance level (14). Thus, there is still some uncertainty regarding
which psychophysiological indicators may be effectively affected by soundscape exposure. Althoughsoundscapes have been widely evidenced to cause positive experience, their health effects have notbeen demonstrated definitively because of methodological and conceptual limitations in priorresearch.
Despite a number of studies dealt with the effects of sounds on adults’ health, none have dealt withsoundscapes for children. Given the widely reported academic stress in primary schools of China,
which impose increasing risk on children’s psychophysiological health, it may be quite urgent task to
explore restorative stimuli that could facilitate stress reduction for children (17). In contrast withannoyed ambient noise, which has been widely proven to have adverse effects on children’s health inprevious studies (18), pleasant soundscapes exhibited restorative potentials as perceived by children(19). Moreover, restorative soundscapes such as water sound was examined to facilitate attentional
restoration for children after a stressful task. Thus, it seems reasonable to expect a positive effect onchildren’s physiological health after exposure to a restorative soundscape. In addition, consideringchildren’s rapidly physical growth, they appear to be more vulnerable to surrounding environments
compared with adults (20), which might leads to different effects of restorative soundscapes onchildren and adults’ health.
Therefore, the aim of this study was to identify the effects of various restorative soundscapes onchildren’s physiological stress. Given the urban parks serve as a major playing environment forchildren to relax and rest, this study was carried out in a simulated urban park situation. During theexperiment, EDA was recorded as measures of physiological stress. It was hypothesized that 1)
exposure to urban park soundscapes could facilitate significant stress recovery and 2) the perceived
restorative soundscapes showed more restorative effects on children’s stress recovery than silence andambient noise in urban parks.

2. METHOD
2.1 Participants
A total of 53 children ranging in age from 8 to 12 years participated in this study (29 boys and 24
girls, mean age=10 years, SD=1.13). Participants were recruited via social media and snowball
sampling in Tianjin, China. All of the children in the study were screened for the normal hearing with
an audiometric examination, and they also reported normal corrected vision. None of them w as taking
prescription medication.
The study was conducted in accordance with the Declaration of Helsinki. Ethical approval was
obtained from the Academic Committee of School of Architecture, Tianjin University. All the children
and their parents were informed about the study protocol, and they voluntarily participated in the study.
Before the experiment, children gave oral consent, and parents gave written informed consent to theresearchers.
2.2 Experimental Stimuli
Urban parks are important and popular places for children to play and relax after school. Therefore,
the context of soundscapes was set as an urban park. A photo of a typical urban park in China waspresented on a screen to simulate a park setting. The picture was shown on a large 46-inch screen,
which was placed in front of the participants as a distance of approximately 100cm.

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Figure 1 – The landscape view of an urban park
Regarding the acoustic stimuli, five potential restorative sounds, i.e. music (MS), stream sound(SS), fountain sound (FS), bell ring (BR), and birdsong (BS) and silence (SL, widely reported to bebeneficial to health) were used as experimental stimuli, while ambient noise (AN) was used ascontrolled stimuli. The five experimental stimuli were indicated to have restorative potential on
children according to our previous study, and the detailed information of the five potential restorative
sounds could be referenced to that study (21). Additionally, the ambient noise was recorded in a typicalurban park in Tianjin, including human voice, water sound, music and some other unclear noise. It is
important to note that, to simulate the real-life settings of urban parks, the above five sounds were used
as dominant sound signals, and separately combined with the urban park noise as a background to
generate five true soundscapes. Specifically, the ambient noise in urban parks was set as 50dBA
according to the general measurement results in previous studies, and a signal to noise (S/N) of 5dB
was reported by children to be the most restorative in a preliminary test. Ther efore, the A-weighted
equivalent sound pressure level of five sounds was set as 55 dBA accordingly. The recording, editing
and calibrating on the soundscape stimuli were processed by Adobe Audition software. During theexperiment, binaural signals of the soundscapes were delivered by computer through headphones(AKG K702).
2.3 Measures
In the current study, electrodermal activity (EDA) expressed in micro-Siemens (µS) was used as themeasure of children’s physiological stress, because it was widely used and suggested as a sensitive
sympathetic indicator. During the experiment, two electrodes were attached to the hypothenar
eminence of the index and middle finger of the participant’s non-dominant hand. The EDA wasmeasured as the conductance between two electrodes with a Biopac EDA100C amplifier. The
measurement data were continuously recorded on a laptop computer with a Biopac System MP160 at
1000Hz and then analyzed using the same software package with which the data were collected(AcqKnowledge 5.0, Biopac).
It is known that there is a delay in the onset of stimulus-evoked physiological activity. Therefore,
the last minute (seconds 60-120s) of the stressful task was used as the stressor period for comparison
with the averaged EDA value during the recovery period. In addition, to further explore the EDA
recovery variation, the 3-min recovery period was divided into six successive 30 second periods.
Moreover, since every individual has a unique EDA baseline, all the measured data during the recovery
period were further calculated as a percentage change (%) from the stressor period to accommodate
individual difference.
2.4 Procedure
The experiments were performed in a semi-anechoic chamber in Tianjin University. Participants
were accompanied by their parents, who waited in a room outside the chamber during the experiment.
Participants took part in the experiment individually, supervised by a researcher.
Participants came to the laboratory and were seated in a comfortable chair where the procedure was
explained. To ensure precise measurements, all the electrodes were initially attached to theparticipant’s body to make sure that the gel on each electrode was fully absorbed into the skin. Before

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the formal experiment, a 3-min quiet baseline level was measured to ensure no group differences
across soundscapes. In addition, due to the limited experiment time and available sample size, eachparticipant attended four experiment sessions which were randomly selected from the total sevensoundscapes. Each session consisted of two parts: 1) a 2-min period of oral calculation testing (stressor
period), which was assessed to be an effective way to induce stress (22), and 2) a 3-min period of
relaxation with exposure to one of the four soundscapes (recovery period), during which participants
were simply instructed to listen to the soundscapes and remain as still as possible. EDA was measured
continuously to record its variations. Then the same session was repeated for the three othersoundscapes. The order of soundscape presentation was randomized and counterbalanced by sex.
Finally, the participants were asked to provide their demographic information, including age in years
and gender. Figure 2 shows a graphical representation of the study protocol. Total time for theexperiment was approximately 30 minutes.

Figure 2 – The graphical representation of the study procedure
2.5 Data Analysis
In this study, all the analysis were done within the SPSS 25.0 software. First of all, the individual
difference across soundscape groups was checked using a nonparametric Kruskal –Willis test (scalevariables) and chi-square test (nominal variables). Then the Wilcoxon signed rank test was conducted
to exam the effectiveness of stress-inducing task. Both of the above steps were the prerequisite before
the following analysis. Due to the hierarchical and repeated-measure nature of the experiment (leading
to autocorrelation), linear mixed models with varying complexities were fit to the data (23). Therefore,a 7 (soundscape) ×6 (time period) mixed-model with restricted maximum likelihood estimation was
conducted to explore for main and interaction effects of soundscape and time on the EDA change. We
also tested for the effects of gender, soundscape by time interaction, soundscape by gender interaction,and time by gender interaction, while the age and baseline measurements were included in the analysis
as covariates. The effect of gender was included as its effects seems evident from previous studies onnoise and health of both adults and children. In all analysis, alpha value less than 0.05 was used as thecriterion to determine significant differences.

3. Result
In this study, 53 children were randomly assigned to four of the seven soundscape groups. Table 1
compared the demographics and baseline characteristics of the children in different soundscape groups.
The results showed there was no significant difference in the demographics and baselinecharacteristics between the seven soundscape groups.
Table 1 – Comparison of sample characteristics between the soundscape groups (n=53)
SL

MS

SS

FS

BR

BS

AN

n=33

n=33

n=30

n=31

n=32

n=30

n=29

Boy

18 (54.5)

17 (51.5)

16 (53.3)

15 (48.4)

16 (53.3)

17 (56.7)

16 (55.2)

Girl

15 (45.5)

16 (48.5)

14 (46.7)

16 (51.6)

14 (46.7)

13 (43.3)

13 (44.8)

Age, M (SD)

10.36

10.30

10.60

10.52

10.38

10.40

10.41

(1.22)(1.21)(1.00)(1.12)(1.29)(1.04)(1.15)

Characteristicsp

Gender, n (%)
.996
.962

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Baseline EDA

8.73

8.83

7.42

6.66

6.68

8.08

7.80

(µS), M (SD)(5.51)(5.27)(5.20)(4.71)(4.42)(5.35)(4.65).556

Regarding the effect of stress-reducing task, the results showed that children’s EDA measuresincreased substantially from the baseline period (M= 7.70, SD=5.02) to the stressor period (M= 13.57,
SD=6.30), which proved that the oral calculation could effectively increase children’s stress level interms of EDA.
Table 2 shows the descriptive statistics, mean values with standard deviations (SD) and medianvalues with Interquartile range (IQR), of EDA measurements during stressor period and recovery
period for each soundscape. Non-parametric Wilcoxon signed rank tests showed that children’s levelsof EDA decreased significantly during the recovery period compared with the stressor period, nomatter what soundscape was exposed to. This result supported our first hypothesis that all urban park
soundscapes could induce stress reduction after an acute stressful task.
Table 2 – Descriptive statistics of EDA data during stressor and recovery period for each soundscape.
Soundscape

EDA-stressor period

EDA-recovery periodpMean(SD)Median(IQR)

Mean(SD)Median(IQR)

SL

14.58 (6.28)

13.78 (8.20)

12.70 (6.47)

11.99 (9.86)

.012

MS

13.40 (6.20)

12.67 (9.82)

10.35 (5.76)

9.54 (6.90)

.000

SS

12.17 (5.36)

12.01 (7.78)

9.56 (5.20)

8.28 (8.53)

.002

FS

14.24 (7.22)

12.45 (10.14)

9.83 (6.20)

8.38 (8.01)

.000

BR

12.89 (5.81)

12.54 (9.84)

9.48 (5.38)

8.66 (9.17)

.000

BS

13.80 (6.34)

12.49 (9.26)

10.67 (6.41)

9.34 (8.59)

.000

AN

14.11 (7.09)

13.63 (8.40)

10.57 (6.51)

9.50 (9.33).000

After controlling for various effects (age and baseline level), the linear mixed model showed a main
effect of soundscape (F=2.24, p=0.040) and time (F=50.88, p=0.000) on the EDA change, but nosignificant interaction between soundscape and time (F=0.80, p=0.768) was found. Specifically,children showed significantly lower EDA during fountain soundscape exposure, compared with
ambient noise exposure. However, there was no significant difference between other soundscapes andambient noise. In addition, children’s EDA levels decreased substantially at the beginning (before 60
seconds) and became relatively stable afterwards, then showed a slight trend of increase at the end of
the recovery period. Nevertheless, none of the soundscapes could decrease children’s EDA to theaveraged baseline level during the entire recovery period, as shown in Figure 3.

EDA (Mean change %)

0

SL
SS
BR
AN

-10

MS
FS
BS
BL

-20
-30
-40
-50
0

30

60

90
120
Time (s)150

180

Figure 3 – Children’s EDA change during exposure to seven soundscapes.
The linear mixed model also showed a significant interaction effect between soundscape andgender on EDA changes (F=2.22. p=0.041). As shown in Figure 4, for boys, ambient noise in urban

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parks could effectively decrease their EDA levels and showed significantly more restorative effects
than silence, and it even induced marginally more stress reduction than other perceived restorative
soundscapes. Meanwhile, for girls, only fountain sound showed significantly more restorative effects
on children’s stress, while no difference was found among other soundscapes.
0
Boys

EDA (Mean change %)

-5

Girls

-10

BL

-15
-20
-25
-30
-35
-40
-45
SL

MS

SS

FS
BR
SoundscapeBS

AN

Figure 4 – Interaction effect of soundscape and gender on EDA.
Additionally, a significant interaction effect was also found between time and gender (F=3.12 .
p=0.009). As shown in Figure 5, during the first 60 seconds of the recovery period, girls’ stress levels
decreased much more than boys and then the girls’ stress reduction became slower than boys. However,boys’ stress levels appeared to slightly increase at the end of the recovery period while girls’ stresslevels continuously decreased.
0
Boys

EDA (Mean change %)

-5

Girls

-10

BL

-15
-20
-25
-30
-35
-40
-45
0

30

60

90
120
Time (s)150

180

Figure 5 – Interaction effect of time and gender on EDA

4. DISCUSSION
In this study, experiments were conducted to examine the actual effects of potential restorative
soundscapes in a (simulated) urban park on children’s stress recovery, based on the physiologicalmeasures of EDA. In line with Hypothesis 1, the results demonstrated that acute exposure to all thesoundscapes could effectively help children recover from a state of induced stress , including theambient noise. Furthermore, a combination with fountain sound with an S/N of 5dB could facilitateeven more stress recovery, at least for girls. It might due to the small fluctuation strength of fountainsound, which made it much easier for children to restore calm and relax. Another possible explanationis that fountain sound could facilitate great masking effect on ambient noise due t o its spectral
frequency characteristics, which is also in line with previous studies (24). However, it is interesting tonote that no other soundscapes showed better restorative effects on stress levels than ambient noise inurban parks. This finding failed to support Hypothesis 2. Moreover, exposure to silence, i.e. simply
reducing the noise level, induced much smaller stress reduction for boys, as compared with ambient
noise. Those results indicated that the ambient noise of urban parks is a qualified restorative
soundscape itself for young children, especially for boys. A possible reason is that children are quite
familiar with the noise, therefore it is not easy to induce large physiological variations. In contrast, the7093

ambient noise in urban parks could enable children to relax and rest to some extent. This result
supported the previous study which suggested familiarity of the environments was positively related torestorativeness (15,25).
However, the study was limited to children between the ages of 8-12 years under settings of urban
parks. This could be a threat to the generalizability of the findings to other settings or samples. It issuggested that conducting similar studies in other settings and in different age groups would test theapplicability of the findings. In addition, the results indicated that different soundscapes showedvaried restorative effects between boys and girls, who also showed different stress reduction tendency
at the end of the recovery period. However, it is less clear whether this tendency will last for a longer
time. Therefore, a longer recovery period should be considered in future studies.

5. CONCLUSIONSIn a simulated situation of an urban park, laboratory experiments were carried out to examine therestorative effects of soundscapes on children’s physiological stress. Based on children’s change of
EDA responses, it was found that the perceived restorative soundscapes in urban parks, including theambient noise, could provide physiological stress recovery for children to some extent after induced
stress. Moreover, the gender difference is an important concern to the restorative effects of different
soundscapes on stress reduction.

ACKNOWLEDGEMENTS
This research was funded by the National Natural Science Foundation of China (grant number
51478303 and 51678401). The authors are also grateful to the children for their participation in thisstudy.

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