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The restorative environmental sounds perceived by children
Journal of Environmental Psychology 60 (2018) 72–80
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Journal of Environmental Psychology journal homepage: www.elsevier.com/locate/jep
The restorative environmental sounds perceived by children Shan Shu, Hui Ma
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T
School of Architecture, Tianjin University, Weijin road 92, Tianjin, China
A R T I C LE I N FO
A B S T R A C T
Handling Editor: Leila Scannell
Previous studies have reported the perceived restorative potential of environmental sounds, but have mainly focused on the perceptions of adults. This study aimed to investigate the restorative environmental sounds based on children's perceptions. In the present experiment, children aged 8–12 (N = 36) were exposed to 32 audiovisual stimuli (2 visual × 16 sound stimuli), the perceived restorativeness of which was assessed using the Perceived Restorative Sounds Scale for Children. A factor analysis revealed three restorative qualities for both natural sounds and urban sounds, and they were interpreted as attractiveness, compatibility and coherence. In addition, a hierarchical cluster analysis was conducted to subdivide the sounds into four categories with different restorative qualities in two contexts. Finally, the results also showed that children's perceived restorative values of environmental sounds were positively correlated with fluctuation strength and sharpness, but negatively correlated with loudness and roughness. Those findings illustrate the restorative potentials of environmental sounds as perceived by children.
Keywords: Environmental sounds Restorative quality children's perception
1. Introduction Currently, it is commonly acknowledged that people experience increasing stress and fatigue in their daily lives (Hartig, Mitchell, de Vries, & Frumkin, 2014). This has resulted in many studies concerned with stress reduction and fatigue restoration and aimed at improving public health. A growing body of literature has indicated that exposure to relatively natural environments provides physical and psychological restoration to both adults and children. In the field of environmental psychology, an environment that promotes restoration could be defined as a restorative environment (Hartig, 2004). Research into restorative environments is generally based on two prominent theories: attention restoration theory (ART) (Kaplan & Kaplan, 1989) and stress recovery theory (SRT) (Ulrich et al., 1991). In particular, ART is concerned with the recovery of the capacity to focus attention, and it suggested four restorative qualities required for producing a restorative environment: engagement of involuntary attention and permission directed attention to recover (fascination), the physical and psychological distance away from the source of mental fatigue (being away), the accordance between an individual's needs and the environment (compatibility), and the scope for involvement and coherence perceived in the environment (extent) (Kaplan, 1995). Based on those restorative qualities, a substantial quantity of work on restoration has been conducted in the past few decades. One key finding is that natural environments are perceived to have better restoration than artificial urban environments
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(Herzog, Chen, & Primeau, 2002; Karmanov & Hamel, 2008). Beyond these subjective reports, experimental studies have confirmed the actual restorative effects of natural views on attentional and physiological recovery (Berto, 2005; Hartig, Evans, Jamner, Davis, & Gärling, 2003; Laumann, Gärling, & Stormark, 2003). Additionally, research in recent years has uncovered some specific environmental components that support restoration. For example, based on 52 university students' ratings of park photos, Nordh, Hartig, Hagerhall, and Fry (2009) found that the variables most predictive of the likelihood of restoration were the size and the vegetation. To date, however, considerable research in this area mainly focused on the restorative effects of visual stimuli (Lindal & Hartig, 2013; Wang, Rodiek, Wu, Chen, & Li, 2016). Although humans rely heavily on vision in environmental perceptions, emerging studies have shown that environmental sounds also play a significant role in restorative experiences in both indoor (Hongistob, Varjo, Oliva, Haapakangas, & Benway, 2017; Ma & Shu, 2018) and outdoor contexts (Carles, Barrio, & De Lucio, 1999; Krzywicka & Byrka, 2017; Payne, 2008). The results of those studies were in line with previous studies on visual stimuli, and natural sounds were perceived to have more restorative potential than urban sounds. For instance, Payne (2013) developed a Perceived Restorativeness Soundscape Scale (PRSS) to evaluate the perceived restorative potential of soundscapes from different environments. Participants were randomly assigned to three audio-visual recordings (i.e. urban, urban park and rural). Results showed that the urban
Corresponding author. No.92 Weijin Road, Nankai District, Tianjin, China. E-mail addresses: [email protected] (S. Shu), [email protected] (H. Ma).
https://doi.org/10.1016/j.jenvp.2018.10.011 Received 2 April 2018; Received in revised form 28 October 2018; Accepted 29 October 2018 Available online 02 November 2018 0272-4944/ © 2018 Elsevier Ltd. All rights reserved.
Journal of Environmental Psychology 60 (2018) 72–80
S. Shu, H. Ma
sounds as perceived by children. A number of natural sounds and urban sounds were assessed by children to extend the understanding of children's restorative perceptions of environmental sounds. Second, based on the restorative qualities above, various environmental sounds in children's living environments were further categorized to discover the sounds with different restorative qualities in children's learning and playing environments. Finally, the psychoacoustic properties of those potential restorative sounds were also investigated to guide the design of restorative soundscapes in children's living environments.
soundscape was perceived to be the least restorative, while the rural soundscape was perceived as the most restorative. Based on PRSS, Payne and Guastavino (2013) also found that the perceived restorativeness of soundscapes was related to the sounds and their temporality, the individual's moods and desires, and the environment. In a study involving semi-structured interviews with 20 adults, birdsong was associated with perceived stress recovery and attention restoration (Ratcliffe, Gatersleben, & Sowden, 2013), and the authors further revealed the imagined perceived restoration of birdsong was connected with its semantic values (Ratcliffe, Gatersleben, & Sowden, 2016). Similarly, Hedblom, Heyman, Antonsson, and Gunnarsson (2014), who recruited 227 young people to rate their reactions to various birdsong combinations in a lecture hall, found that birdsong by several species was more highly appreciated than that by a single species. The literature mentioned above mostly focused on the perceived restoration of nature-related sounds, whilst empirical research regarding the actual restoration of environmental sounds is rather limited and needs to be adequately tested. For example, a physiological study, which was conducted with 40 participants’ exposure to different experimental sounds, confirmed that nature sounds promoted faster skin conductance recovery than environmental noise, but heart rate variability showed no effects of different sounds (Alvarsson, Wiens, & Nilsson, 2010). A between-subjects study used a backwards digit-span task to measure cognitive recovery after exposure to different sounds, but participants who were exposed to natural sounds were not significantly different than those exposed to anthropogenic sounds (Abbott, Taff, Newman, Benfield, & Mowen, 2016). Regarding emotional restoration, Benfield, Taff, Newman, and Smyth (2014) showed that natural sounds provide greater mood recovery compared to anthropogenic sounds. However, the study outcomes were only reliant on self-reported mood. This was similar to a study of open-plan office sounds, which showed significant restoration on a self-reported experience of fatigue, but not on cognitive and physiological measures (Jahncke, Hygge, Halin, Green, & Dimberg, 2011). Nevertheless, those previous studies did find evidence of the restorative potential of environmental sounds. However, most existing studies on the restorative potentials of environmental sounds has been done with adults, while children's perceptions were rarely considered. Different from adults, children's physical and psychological health is in a stage of high-speed development, and children's development could be directly influenced by physical environments (Evans, 2006). However, there has been inadequate attention paid to the physical and psychological needs of children in their living environment (Elsley, 2004). In addition, it has been indicated that children might experience high levels of stress and fatigue (Crook, Beaver, & Bell, 1998), which might be especially serious in China. Several social surveys conducted in Chinese primary schools found that the increasingly competitive educational environment has led to high levels of academic stress and fatigue (Hesketh et al., 2010). Therefore, children generally have an urgent need for stress reduction and fatigue recovery. Although many studies have been conducted to explore the restorative effects of the natural environment on children's health (Bagot, Kuo, & Allen, 2007; Bagot, Allen, & Toukhsati, 2015; Korpela, KyttÄ, & Hartig, 2002; Wells, 2000), little is yet known about the potential of restorative sounds for children. Exposure to environmental noise, such as traffic noise in school and at home, has been shown to have adverse effects on children's emotional health and cognitive performance by numerous studies (Evans, Lercher, Meis, Ising, & Kofler, 2001; Shield & Dockrell, 2003). However, whether the pleasant sounds such as birdsong and water sounds have positive effects on children deserves further study. Therefore, the present study employed a laboratory experiment to explore the restorative environmental sounds as perceived by children. Specifically, there were three sub-goals in this study. First, since children's perception of environmental sounds is different from adults, the first goal was to investigate the restorative qualities of environmental
2. Methodology 2.1. Participants According to Piaget's theory of cognitive development (Piaget, 1964) and the task requirement of the children's comprehensive ability, children aged 8–12 were chosen as participants. The sample size of each age and gender was paralleled as much as possible. Altogether, 36 children (mean age = 10.03 years, SD = 1.42) took part in the study, including 19 boys and 17 girls. In addition, each of the five age brackets was comprised of at least three boys and three girls to further analyse possible age differences. Participants were recruited from various primary schools in Tianjin, China, and all the participants reported that they had normal hearing and normal vision. All the children and their parents were informed about the study protocol, and they were voluntary to participate in the study. Before participation, the children gave oral consent, and parents gave written informed consent to the researchers. The project was approved by the Institutional Academic Board of Tianjin University. 2.2. Experiment stimuli To determine the sound stimuli to be used in the study, a questionnaire was given to 335 children (170 boys and 165 girls) aged 7–12 in six primary school classrooms and four urban parks of Tianjin, China, before the study. Prior research has shown that familiarity and preference of the stimuli were highly correlated with restoration (Purcell, Peron, & Berto, 2001). Therefore, children were asked to choose their familiar sounds and preferred sounds in the survey sites from a list of sounds in the questionnaire. As a result, 10 most familiar sounds and 10 most preferred sounds were selected. Notably, four of the selected 20 sounds were chosen as both highly familiar and preferred sounds by children. Therefore, a total of 16 environmental sounds were obtained, consisting of eight natural sounds (generated by natural resources) and eight urban sounds (generated by urban environments and human activities). The natural sounds included trees rustling, sea waves, stream sounds, birdsongs, fountain sounds, frogs croaking, rain and cicadas chirping. The urban sounds included singing, bells ringing, traffic noise, footsteps, construction sounds, human voices, children frolicking and music. The sound stimuli were collected from multiple databases and supplemented by recordings made by the researchers. These recordings were made in classrooms and urban parks in Tianjin during March to July 2017, and a series of 30s sound stimuli were recorded using a Sony PCM-D50 audio recorder. All the sound stimuli were stored in uncompressed wave digital format and converted into the same sample rate and size of 44.1 kHz 16 bit. In addition, according to previous studies, 55dBA was considered the most appropriate sound level by participants because at that level they could hear the sound stimuli clearly but did not feel annoyed by it (Ma & Shu, 2018). Therefore, the sound level of all the sound stimuli was set at 55 dBA, and the duration of each sound was set at 2 min which was thought to be appropriate to complete the experiment tasks by children according to the preliminary experiment. The sound stimuli were played back by a computer through headphones (AKG K702) in the experiment. Some studies have found that audio-visual interaction plays an 73
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Fig. 1. Two simulated environments: school classrooms (left) and urban parks (right).
important role in environmental perceptions (Preis, Kociński, HafkeDys, & Wrzosek, 2015). Moreover, the sounds' meaning within context is an important element in the perceivers' assessment (Payne, Davies, & Adams, 2009). Therefore, the visual contexts of the environmental sounds were also considered in this study. This study was carried out in two simulated visual contexts: school classrooms and urban parks, and a preliminary test was conducted to select the pictures of those two contexts. Ten pictures of classrooms and urban parks taken in Tianjin were rated by children in terms of representativeness of the place. The picture that obtained the highest scores was used to help children visualize the context referred to in the questionnaire (Fig. 1). Classrooms and urban parks were selected for the following reasons. First, they were the most accessible places and most frequently visited by children in China. Second, they were representative of environments with different functions. School classrooms are typical built environments for children's study and development, while urban parks are typical natural environments for children's amusement and relaxation in urban areas. The pictures were shown on a large 46-inch screen, which was placed in front of the participants at a distance of approximately 100 cm.
Table 1 Perceived Restorativeness Sound Scale items grouped by Attention Restoration Theory. Fascination 1. I find this sound appealing. 2. I find this sound interesting. 3. This sound makes me want to hear more. 4. This sound makes me imagine. 5. I am immersed in this sound. Being away 6. I rarely hear this special sound. 7. This is a different sound from what I usually hear. 8. When I hear this sound here, I like to do something different than I usually do. 9. When I hear this sound here, I feel free from study and homework. 10. When I hear this sound here, I feel free from stress and annoyance. 11. Listening to this sound here offers me a period of relaxation. Compatibility 12. This sound environment fits with my personal preferences. 13. I will soon get used to hearing this sound here. 14. This sound environment relates to activities I like to do. Coherence 15. The sound I am hearing belongs here (with the place shown). 16. The sound I am hearing seems quite harmonious with this place.
2.3. Measurements To assess the restorative potential of environmental sounds, the PRSS (Payne, 2013) was employed and revised in relation to a specific environmental sound rather than the whole soundscape. In addition, as the participants in this study were children, the PRSS was also revised according to the Perceived Restorative Components Scale for Children developed by Bagot et al. (2007). Then the revised Perceived Restorative Sound Scale for children (PRSS-C) was translated from English to Chinese by two authors and back-translated by a fluent speaker of both languages. A high similarity between the English and Chinese translations was found. Finally, the questionnaire was pre-tested with five children to ensure that children could comprehend the items easily and accurately. The final 16-item PRSS-C consisted of four components according to ART: fascination, being away, compatibility and coherence. Fascination was measured by five items; Being away was measured by six items; Compatibility was measured by three items; and Coherence was measured by two items (Table 1). Each item was assessed on a 5-point scale (0 = Not at all, 1 = Slightly, 2 = Moderately, 3 = Very, 4 = Extremely). These were converted in the process of analyses from 1 = low restorativeness to 5 = high restorativeness. In addition, the questionnaire also included children's personal information, such as gender and age.
Fig. 2. Photo of a semi-anechoic chamber with two participants performing the experiment.
from outside sounds and ensure that the sound environment is kept constant. Participants were accompanied by their parents who waited in a room outside the chamber during the experiment. Participants took part in the experiment two at a time, supervised by a researcher (Fig. 2). During the experiment, each participant was first asked to imagine a scenario to induce his or her emotional stress and attention fatigue, which was proven to be an effective method to raise stress and fatigue levels (Staats, Kieviet, & Hartig, 2003). Since the experiment was conducted when children had just finished their final exams and began their summer holiday, the text was slightly revised according to
2.4. Procedure The experiment was performed in mid-2017 (July to September) in a semi-anechoic chamber in Tianjin University, which is commonly used for acoustics and equipped with sound absorbing wedges to provide a free field condition with low background noise (20-25dBA). Such chambers can be used as an ideal listening room to avoid disturbance 74
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Fig. 3. Diagram of experimental procedure.
children's actual conditions. Researchers read the text as follows: ‘This semester, you have studied very hard. Now, at the end of the final exams, you have been asked to do a lot of homework. You have difficulty concentrating, and you are very anxious because of concerns about test scores’. Then, the audio-visual stimuli were presented, and participants were asked to imagine that they were actually in the midst of the present setting. After exposure to each audio-visual stimulus for 10s without doing anything, children were asked to circle the answer on each PRSS-C item while the audio-visual stimulus was continuously displayed. The time for completing the questionnaire was adjusted according to each participant's individual needs, and there was a 10s interval to refresh before exposure to the next audio-visual stimuli. Each stimulus took about 2 min to be evaluated (Fig. 3). A total of 32 audio-visual stimuli (2 visual × 16 sound stimuli) were presented and evaluated by each participant. Half of the children were first exposed to the photo of classrooms and then urban parks, while the order was reversed for the others. In addition, the 16 sound stimuli were counterbalanced in random order to minimize order effects. Furthermore, the whole procedure was divided into three parts of 20min each with two periods of 15-min rest between them to avoid fatigue and impatience (about 90 min totally). Finally, participants completed the basic sociodemographic data. The whole procedure was pre-tested before the formal experiments to ensure that it was appropriate for an 8–12 age group.
collected data of all environmental sounds. The Kaiser-Meyer-Olkin index (0.909) and Bartlett's test of sphericity ( χ 2 =15152.78, p < .001) indicated the adequacy of the sample size for conducting a factor analysis. Given the convergence of the scree plot and Kaiser's criterion (eigenvalues are greater than 1), results showed that three underlying factors were extracted from 16 items (Table 2). Factor 1 (40.06%) consisted of 11 items; factor 2 (20.41%) included three items; and factor 3 (11.75%) consisted of two items. The three factors covered 72.21% of the total variance, and Cronbach's alpha was above 0.80 for each factor. The correlations between the three factors and each item with the high-correlation data (above 0.5) were highlighted. To examine whether there was a difference in restorative qualities between natural sounds and urban sounds, factor analysis was then conducted twice based on the data of natural sounds and urban sounds, respectively. Similar results were obtained in both contexts. This indicated that the three-factor structure was suitable for all kinds of environmental sounds to a certain extent. Overall, there were three restorative qualities of environmental sounds as perceived by children, and they could be interpreted as attractiveness, compatibility and coherence, respectively. 3.2. The potential restorative sounds perceived by children The restorative values of the eight natural sounds and eight urban sounds evaluated by the children were first compared using non-parametric Mann-Whitney U tests, given the non-normality of the raw data distribution. The results showed that natural sounds were perceived as more restorative than urban sounds (p < .001 for attractiveness; p < .01 for compatibility; p < .05 for coherence). However, some urban sounds were perceived to be more restorative than most natural sounds, such as music, singing, and bells ringing (Fig. 4). Therefore, merely dividing the environmental sounds into natural and urban was not appropriate. The environmental sounds should be further classified in different contexts based on their perceived restorative qualities. With the three restorative qualities, 16 environmental sounds were clustered using hierarchical cluster analysis (Fig. 5). Based on squared Euclidean distances among the sounds, four categories were created in both classrooms and urban parks. In classrooms, most natural sounds were clustered in category 1, while urban sounds were divided into categories 2 (music-like sounds), 3 (human voices), and 4 (artificial sounds). In urban parks, natural sounds were divided into categories 1 (general natural sounds) and 3 (animal sounds), while urban sounds were divided into categories 2 (music-like sounds) and 4 (general urban sounds). When comparing the classification of sounds in those two contexts, it could be seen that urban sounds were further classified in classrooms and natural sounds were further classified in parks. In addition, it was also interesting to note that category 2 in these two contexts consisted of the same sounds (i.e. singing and music), which indicated that the restorative qualities of music-like sounds have no difference between contexts, at least for children. The perceived restorative qualities of different sound categories were further compared (Fig. 6). As the mean values of environmental sounds were normally distributed, Bonferroni post-hoc comparisons
2.5. Statistical analysis Statistical analysis was performed with SPSS 22.0. Specifically, a factor analysis was used to investigate the restorative qualities of environmental sounds as perceived by children. In particular, principal component method (a factor-extraction procedure) and variance maximization (i.e. Varimax, an orthogonal rotational strategy) were chosen during the factor analysis (Fabrigar, Wegener, MacCallum, & Strahan, 1999) to identify the underlying common factors of 16 correlated variables in PRSS-C. In addition, to explore the potential restorative sounds as perceived by children in different contexts, a hierarchical cluster analysis was performed among the 16 environmental sounds based on Ward's method algorithm (Murtagh & Legendre, 2014). A Bonferroni post-hoc test, which is recommended as a relatively conservative test to compensate for spurious significant results that occur with multiple comparisons, was conducted to further compare the perceived restorative qualities of each sound category. Finally, a nonparametric Spearman rank correlation matrix was created to investigate the relationship between psychoacoustic parameters and perceived restorative values, and non-parametric tests (Mann-Whitney U-tests and Kruskal-Wallis tests) were used to explore the influence of personal attributes and contexts on children's perceptions. 3. Results 3.1. The restorative qualities of environmental sounds perceived by children A factor analysis was conducted to investigate the restorative qualities of environmental sounds as perceived by children, using the 75
Journal of Environmental Psychology 60 (2018) 72–80
.18 .15 .14 .92 .91 .18
.34 .24 .34 .31 .33 -.21 -.13 .28 .39 .43 .43 .87 .88 .81 .15 .17 .77 .78 .79 .69 .74 .74 .79 .66 .72 .75 .73 .18 .18 .35
.17
.11
.73 .69 .75 .57 .67 .60 .66 .52 .67 .75 .72 .81 .82 .80 .88 .88
were conducted. With regard to school classrooms, music-like sounds (category 2) were shown to be the most restorative sounds in terms of attractiveness and compatibility, followed by generally natural sounds (category 1). Human voice (category 3) showed the highest values of coherence, whereas artificial sounds (category 4) showed the lowest restorative values in all three qualities. With regard to urban parks, both music-like sounds (category 2) and animal sounds (category 3) showed the highest restorative values. However, animal sounds showed a higher value of coherence than music-like sounds. General natural sounds (category 1) were moderate in the three restorative qualities followed by general urban sounds (category 4). It was notable that the values of the three restorative qualities were quite different from one another in both contexts. The values of compatibility were generally higher than the values of attractiveness and coherence. However, the values of coherence were the highest for the environmental sounds of category 3. This means that the coherence of sound and context was the most important restorative quality for category 3 in both contexts. Moreover, to investigate the restorative values of each environmental sound, the 16 sound samples were plotted into two-dimensional coordinate systems (Fig. 7). In classrooms, music and singing were perceived by children as the most restorative sounds, while construction sounds and traffic noise were perceived as the least restorative sounds. In addition, music was the most attractive and compatible sound, and children frolicking was the most coherent sound. In urban parks, music and singing were also perceived by children as the most restorative sounds, while most urban sounds, such as construction sound, were perceived as the least restorative sounds. Similar to classrooms, music was also the most attractive and compatible sound. However, natural sounds (i.e. birdsong and cicadas chirping) were most coherent with the environment of urban parks.
.19 .13 .93 .94
3.3. The factors influencing the restorative qualities of environmental sounds
.11
.80 .81 .80 .69 .71 .75 .78 .74 .77 .76 .70 .20 .16 .35
.24 .29 .32 .36 .89 .90 .83 .15 .16
.15 .19
.11 .17 .11 .23 .22 .22 .33 .34 -.11
.70 .73 .71 .59 .62 .58 .60 .61 .69 .70 .66 .84 .88 .83 .90 .92
3 (12.14%) 2 (19.36%)
To identify the acoustic characteristics of the environmental sounds that contributed to the children's restorative perceptions, five psychoacoustic parameters—loudness, fluctuation strength, sharpness, roughness, and tonality—were analysed for each sound. Loudness is defined as the magnitude of an auditory sensation. Fluctuation strength is the sensation with slower changes in sound. Sharpness is caused by high-frequency components in sound. Roughness is related to the beating phenomenon, or relatively quick changes of sound. Tonality indicates whether sound consists mainly of tonal components or broadband noise (Zwicker & Fastl, 2013). For each sound, the five parameters were calculated by ArtemiS software (HEAD acoustics) in terms of the mean values over 30s, as reported in Table 3. The relationship between the three restorative qualities and five psychoacoustic parameters showed that the perceived restorative values of environmental sounds were positively correlated with fluctuation strength and sharpness to some extent, but negatively correlated with loudness and roughness. However, the three qualities had no correlations with tonality. In addition, the influence of children's personal information (i.e. age and gender) and the contexts on their restorative perceptions were analysed (Table 4). The results showed the children's perceptions of attractiveness and compatibility were significantly different between genders. Similarly, there was also a significant difference between age groups in terms of attractiveness, compatibility and coherence. Moreover, contexts only had a significant effect on the perception of coherence.
.14
.27 .35 .39 .40 .87 .89 .82 .15 .17 Coherence
Compatibility
Being away
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Fascination
Items with the high-correlation data (above 0.5) are indicated with a bold front.
.12 .14 .17 .14 .93 .92
.71 .71 .73 .59 .65 .60 .63 .57 .68 .73 .69 .82 .85 .81 .90 .90 .30 .24 .29 .32 .34 -.16
.78 .79 .80 .69 .72 .76 .79 .70 .75 .75 .72 .19 .17 .36
.11 .16
Communalities 3 (11.75%) 2 (20.41%) 1 (40.06%)
Overall sounds PRSS-C Items Restorative qualities in ART
Table 2 Factor analysis of overall sounds, natural sounds, and urban sounds.
.11 .16
2 (21.22%) 1 (39.30%) 1 (40.56%)
Communalities
Urban sounds Natural sounds
3 (11.57%)
Communalities
S. Shu, H. Ma
4. Discussion The first aim of this study was to investigate the restorative qualities of environmental sounds as perceived by children. The results showed 76
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Fig. 4. Perceived restorative values of each environmental sound.
Fig. 5. Dendrogram for 16 environmental sounds by hierarchical cluster analysis (Left: School classrooms; Right: Urban parks).
Fig. 6. Perceived restorative values of different sound categories in school classrooms (Category 1: natural sounds; Category 2: music-like sounds; Category 3: human voice; Category 4: artificial sounds) and urban parks (Category 1: general natural sounds; Category 2: music-like sounds; Category 3: animal sounds; Category 4: general urban sounds).
different with extent for visual environments, as coherence in this study indicated the coherent interrelationship between environmental sounds and their visual contexts. Overall, it is likely that people's restorative perceptions of visual environments are more complicated. A possible reason is that visual environments vary in terms of the number and type of visual elements compared to the specific sound sources used in this study. Second, this study revealed the possibility of a difference between children and adults in the perceptions of environmental sounds, as compared with the study of Payne (2013). However, this finding should be confirmed by future studies with a larger sample size. Based on the three restorative qualities above, we also found that
that for children, three subjective qualities were required for a restorative sound, including attractiveness, compatibility, and coherence. This result was quite different from the restorative qualities of visual environments and acoustic environments as perceived by adults. First, the number of restorative qualities of environmental sounds in this study was fewer than those of visual environments (i.e. fascination, being away, compatibility, and extent) (Laumann, GÄRling, & Stormark, 2001). Fascination and being away were merged into attractiveness for sounds, which represented the inherent qualities of sounds to allow attentional recovery and emotional relaxation. Additionally, the meaning of coherence for environmental sounds was also 77
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Fig. 7. Restorative qualities of each environmental sound in school classrooms (Category 1: natural sounds; Category 2: music-like sounds; Category 3: human voice; Category 4: artificial sounds) and urban parks (Category 1: general natural sounds; Category 2: music-like sounds; Category 3: animal sounds; Category 4: general urban sounds).
potential restorative sounds perceived by children were quite consistent with those in classrooms. However, the most coherent environmental sounds were quite different between the two contexts. Compared to the most coherent sounds (i.e. human voices and children frolicking) in classrooms, natural sounds (i.e. birdsong and cicadas chirping) not only showed the highest coherence in urban parks, but also showed a great quality of attractiveness and compatibility. Therefore, it might be possible to achieve actual restorative effects on children when they were exposed to birdsong and cicadas chirping in urban parks. In addition, the coherence of environmental sounds was found to vary significantly in different contexts. This finding confirmed the importance of audio-visual coherence in environmental perceptions,
the restorative sounds for children were somewhat different than those for adults, especially in the context of built environments. For children, urban sounds such as singing and music were perceived as the most restorative sounds in classrooms, while adults usually prefer natural sounds in built environments (Yu, Behm, Bill, & Kang, 2017). Certainly, for children, natural sounds are still perceived to be more restorative than most common urban sounds. Therefore, music, singing, and most natural sounds might be considered as potential restorative sounds in school classrooms, while other urban sounds should be reduced as much as possible. In particular, the sounds of human voices and children frolicking should be controlled properly because these are the most coherent sounds and inevitable in classrooms. In urban parks, the 78
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Table 3 Mean values of psychoacoustics characteristics of 16 environmental sounds.
Mean values Singing Trees rustling Bell ringing Sea waves Traffic noise Footsteps Stream sound Birdsong Fountain sound Construction sound Human voice Frogs croaking Children frolicking Music Raining Cicadas chirping
Loudness (sone GF)
Fluctuation strength (vacil)
Sharpness (acum)
Roughness (asper)
Tonality (tu)
10.70 11.80 4.96 12.30 15.30 10.00 7.21 4.33 7.99 5.42 10.20 3.19 9.12 8.67 7.52 6.29
0.0228 0.0063 0.0128 0.0050 0.0104 0.0542 0.0304 0.0542 0.0042 0.0277 0.0354 0.0081 0.0197 0.0547 0.0046 0.0027
1.11 1.64 3.47 1.66 1.33 1.72 1.76 1.86 1.96 1.45 1.14 1.78 1.47 1.04 1.98 2.37
0.85 1.67 0.24 1.60 1.46 2.27 2.25 0.15 1.63 1.12 1.29 0.39 1.32 0.78 1.51 0.50
0.6320 0.0390 0.4750 0.0216 0.0594 0.0182 0.0076 0.0126 0.0262 0.0451 0.0888 0.0279 0.1570 0.7080 0.0227 0.0326
.08** .05 .06
.06* .01 .06*
−.19** −.10** −.19**
-.01 .00 .02
Spearman's correlation coefficients Attractiveness −.14** Compatibility −.06 Coherence −.14**
Significant correlations with ** as p < .01 and * as p < .05.
experience. This is because we were less interested in the acoustic characteristics of environmental sounds than the restorative perceptions they produce. Certainly, many acoustic parameters have the potential to affect children's restorative perceptions. From the standpoint of intervention, we believe that if we better understand which acoustic parameters most affect children's restorative perceptions of sounds, it will be easier to decide which particular sound needs to be considered in the environmental design. Therefore, future research is necessary to determine how other acoustic parameters contribute to the perceived restorativeness of environmental sounds. Moreover, future research is also required to show whether the findings are generalizable to other environmental sounds and more children.
Table 4 The influence of children's gender, age, and contexts on sounds' restorative qualities.
Attractiveness Compatibility Coherence
Gender
Age
Context
.00** .00** .94
.00** .00** .03*
.42 .47 .00**
Significant difference with ** as p < .01 and * as p < .05.
which was in accordance with many previous studies (Ma & Shu, 2018). We also found significant correlations between children's restorative perceptions and sounds' fluctuation strength, sharpness, loudness, and roughness. This indicated that the restorative potential of environmental sounds could be predicted using their psychoacoustic parameters to a certain extent. Although further examinations with more sound samples are still needed, this study enriches existing research and allows for further exploration of the mechanism behind the influence of psychoacoustic parameters on the restorativeness of sounds. Finally, children's restorative perceptions of environmental sounds were also found to be significantly influenced by their gender and age. Therefore, the future design of children's acoustic environment should consider children's individual characteristics. Despite the contributions described above, there are a few limitations that should be noted when interpreting the results. First, this is a laboratory study using photographs to simulate contexts of school classrooms and urban parks. Therefore, the sense of immersion might be quite poor. Nevertheless, by controlling variables in a laboratory setting, this study confirmed the perceived restorative qualities of sounds in a strict causal sense. Second, this study focused on children's perceptions of restorative qualities instead of examining their actual restoration. Although the results are in line with previous studies highlighting the experienced restoration of environmental sounds, further work is needed to establish that such sounds will reduce stress or fatigue. Recent studies have shown that adults' restorative experience of a soundscape is related to their physiological response (Alvarsson et al., 2010; Medvedev, Shepherd, & Hautus, 2015). Therefore, we believe that this study lays a foundation for future research, which will examine the actual restorative effects of environmental sounds on children. Third, this study only investigated the influence of a few psychoacoustic parameters on the restorative
5. Conclusion Based on the children's subjective evaluation, three key restorative qualities were revealed for a potential restorative sound, which were interpreted as attractiveness, compatibility, and coherence. Based on the three restorative qualities, environmental sounds were subdivided into four categories each in the context of school classrooms and urban parks. For both contexts, music-like sounds, such as singing and music, were perceived to be the most attractive and compatible sounds, followed by general natural sounds. However, the most coherent sounds were different in the two contexts. Furthermore, the perceived restorative values of environmental sounds were found to be significantly influenced by their psychoacoustic parameters, children's personal information, and visual contexts. Therefore, it is important to consider designing restorative soundscapes to improve the restorative experience in children's living environments.
Acknowledgements This work was supported by the National Natural Science Foundation of China [Project No. 51478303, 51678401].
Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.jenvp.2018.10.011. 79
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Journal of Environmental Psychology journal homepage: www.elsevier.com/locate/jep
The restorative environmental sounds perceived by children Shan Shu, Hui Ma
∗
T
School of Architecture, Tianjin University, Weijin road 92, Tianjin, China
A R T I C LE I N FO
A B S T R A C T
Handling Editor: Leila Scannell
Previous studies have reported the perceived restorative potential of environmental sounds, but have mainly focused on the perceptions of adults. This study aimed to investigate the restorative environmental sounds based on children's perceptions. In the present experiment, children aged 8–12 (N = 36) were exposed to 32 audiovisual stimuli (2 visual × 16 sound stimuli), the perceived restorativeness of which was assessed using the Perceived Restorative Sounds Scale for Children. A factor analysis revealed three restorative qualities for both natural sounds and urban sounds, and they were interpreted as attractiveness, compatibility and coherence. In addition, a hierarchical cluster analysis was conducted to subdivide the sounds into four categories with different restorative qualities in two contexts. Finally, the results also showed that children's perceived restorative values of environmental sounds were positively correlated with fluctuation strength and sharpness, but negatively correlated with loudness and roughness. Those findings illustrate the restorative potentials of environmental sounds as perceived by children.
Keywords: Environmental sounds Restorative quality children's perception
1. Introduction Currently, it is commonly acknowledged that people experience increasing stress and fatigue in their daily lives (Hartig, Mitchell, de Vries, & Frumkin, 2014). This has resulted in many studies concerned with stress reduction and fatigue restoration and aimed at improving public health. A growing body of literature has indicated that exposure to relatively natural environments provides physical and psychological restoration to both adults and children. In the field of environmental psychology, an environment that promotes restoration could be defined as a restorative environment (Hartig, 2004). Research into restorative environments is generally based on two prominent theories: attention restoration theory (ART) (Kaplan & Kaplan, 1989) and stress recovery theory (SRT) (Ulrich et al., 1991). In particular, ART is concerned with the recovery of the capacity to focus attention, and it suggested four restorative qualities required for producing a restorative environment: engagement of involuntary attention and permission directed attention to recover (fascination), the physical and psychological distance away from the source of mental fatigue (being away), the accordance between an individual's needs and the environment (compatibility), and the scope for involvement and coherence perceived in the environment (extent) (Kaplan, 1995). Based on those restorative qualities, a substantial quantity of work on restoration has been conducted in the past few decades. One key finding is that natural environments are perceived to have better restoration than artificial urban environments
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(Herzog, Chen, & Primeau, 2002; Karmanov & Hamel, 2008). Beyond these subjective reports, experimental studies have confirmed the actual restorative effects of natural views on attentional and physiological recovery (Berto, 2005; Hartig, Evans, Jamner, Davis, & Gärling, 2003; Laumann, Gärling, & Stormark, 2003). Additionally, research in recent years has uncovered some specific environmental components that support restoration. For example, based on 52 university students' ratings of park photos, Nordh, Hartig, Hagerhall, and Fry (2009) found that the variables most predictive of the likelihood of restoration were the size and the vegetation. To date, however, considerable research in this area mainly focused on the restorative effects of visual stimuli (Lindal & Hartig, 2013; Wang, Rodiek, Wu, Chen, & Li, 2016). Although humans rely heavily on vision in environmental perceptions, emerging studies have shown that environmental sounds also play a significant role in restorative experiences in both indoor (Hongistob, Varjo, Oliva, Haapakangas, & Benway, 2017; Ma & Shu, 2018) and outdoor contexts (Carles, Barrio, & De Lucio, 1999; Krzywicka & Byrka, 2017; Payne, 2008). The results of those studies were in line with previous studies on visual stimuli, and natural sounds were perceived to have more restorative potential than urban sounds. For instance, Payne (2013) developed a Perceived Restorativeness Soundscape Scale (PRSS) to evaluate the perceived restorative potential of soundscapes from different environments. Participants were randomly assigned to three audio-visual recordings (i.e. urban, urban park and rural). Results showed that the urban
Corresponding author. No.92 Weijin Road, Nankai District, Tianjin, China. E-mail addresses: [email protected] (S. Shu), [email protected] (H. Ma).
https://doi.org/10.1016/j.jenvp.2018.10.011 Received 2 April 2018; Received in revised form 28 October 2018; Accepted 29 October 2018 Available online 02 November 2018 0272-4944/ © 2018 Elsevier Ltd. All rights reserved.
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sounds as perceived by children. A number of natural sounds and urban sounds were assessed by children to extend the understanding of children's restorative perceptions of environmental sounds. Second, based on the restorative qualities above, various environmental sounds in children's living environments were further categorized to discover the sounds with different restorative qualities in children's learning and playing environments. Finally, the psychoacoustic properties of those potential restorative sounds were also investigated to guide the design of restorative soundscapes in children's living environments.
soundscape was perceived to be the least restorative, while the rural soundscape was perceived as the most restorative. Based on PRSS, Payne and Guastavino (2013) also found that the perceived restorativeness of soundscapes was related to the sounds and their temporality, the individual's moods and desires, and the environment. In a study involving semi-structured interviews with 20 adults, birdsong was associated with perceived stress recovery and attention restoration (Ratcliffe, Gatersleben, & Sowden, 2013), and the authors further revealed the imagined perceived restoration of birdsong was connected with its semantic values (Ratcliffe, Gatersleben, & Sowden, 2016). Similarly, Hedblom, Heyman, Antonsson, and Gunnarsson (2014), who recruited 227 young people to rate their reactions to various birdsong combinations in a lecture hall, found that birdsong by several species was more highly appreciated than that by a single species. The literature mentioned above mostly focused on the perceived restoration of nature-related sounds, whilst empirical research regarding the actual restoration of environmental sounds is rather limited and needs to be adequately tested. For example, a physiological study, which was conducted with 40 participants’ exposure to different experimental sounds, confirmed that nature sounds promoted faster skin conductance recovery than environmental noise, but heart rate variability showed no effects of different sounds (Alvarsson, Wiens, & Nilsson, 2010). A between-subjects study used a backwards digit-span task to measure cognitive recovery after exposure to different sounds, but participants who were exposed to natural sounds were not significantly different than those exposed to anthropogenic sounds (Abbott, Taff, Newman, Benfield, & Mowen, 2016). Regarding emotional restoration, Benfield, Taff, Newman, and Smyth (2014) showed that natural sounds provide greater mood recovery compared to anthropogenic sounds. However, the study outcomes were only reliant on self-reported mood. This was similar to a study of open-plan office sounds, which showed significant restoration on a self-reported experience of fatigue, but not on cognitive and physiological measures (Jahncke, Hygge, Halin, Green, & Dimberg, 2011). Nevertheless, those previous studies did find evidence of the restorative potential of environmental sounds. However, most existing studies on the restorative potentials of environmental sounds has been done with adults, while children's perceptions were rarely considered. Different from adults, children's physical and psychological health is in a stage of high-speed development, and children's development could be directly influenced by physical environments (Evans, 2006). However, there has been inadequate attention paid to the physical and psychological needs of children in their living environment (Elsley, 2004). In addition, it has been indicated that children might experience high levels of stress and fatigue (Crook, Beaver, & Bell, 1998), which might be especially serious in China. Several social surveys conducted in Chinese primary schools found that the increasingly competitive educational environment has led to high levels of academic stress and fatigue (Hesketh et al., 2010). Therefore, children generally have an urgent need for stress reduction and fatigue recovery. Although many studies have been conducted to explore the restorative effects of the natural environment on children's health (Bagot, Kuo, & Allen, 2007; Bagot, Allen, & Toukhsati, 2015; Korpela, KyttÄ, & Hartig, 2002; Wells, 2000), little is yet known about the potential of restorative sounds for children. Exposure to environmental noise, such as traffic noise in school and at home, has been shown to have adverse effects on children's emotional health and cognitive performance by numerous studies (Evans, Lercher, Meis, Ising, & Kofler, 2001; Shield & Dockrell, 2003). However, whether the pleasant sounds such as birdsong and water sounds have positive effects on children deserves further study. Therefore, the present study employed a laboratory experiment to explore the restorative environmental sounds as perceived by children. Specifically, there were three sub-goals in this study. First, since children's perception of environmental sounds is different from adults, the first goal was to investigate the restorative qualities of environmental
2. Methodology 2.1. Participants According to Piaget's theory of cognitive development (Piaget, 1964) and the task requirement of the children's comprehensive ability, children aged 8–12 were chosen as participants. The sample size of each age and gender was paralleled as much as possible. Altogether, 36 children (mean age = 10.03 years, SD = 1.42) took part in the study, including 19 boys and 17 girls. In addition, each of the five age brackets was comprised of at least three boys and three girls to further analyse possible age differences. Participants were recruited from various primary schools in Tianjin, China, and all the participants reported that they had normal hearing and normal vision. All the children and their parents were informed about the study protocol, and they were voluntary to participate in the study. Before participation, the children gave oral consent, and parents gave written informed consent to the researchers. The project was approved by the Institutional Academic Board of Tianjin University. 2.2. Experiment stimuli To determine the sound stimuli to be used in the study, a questionnaire was given to 335 children (170 boys and 165 girls) aged 7–12 in six primary school classrooms and four urban parks of Tianjin, China, before the study. Prior research has shown that familiarity and preference of the stimuli were highly correlated with restoration (Purcell, Peron, & Berto, 2001). Therefore, children were asked to choose their familiar sounds and preferred sounds in the survey sites from a list of sounds in the questionnaire. As a result, 10 most familiar sounds and 10 most preferred sounds were selected. Notably, four of the selected 20 sounds were chosen as both highly familiar and preferred sounds by children. Therefore, a total of 16 environmental sounds were obtained, consisting of eight natural sounds (generated by natural resources) and eight urban sounds (generated by urban environments and human activities). The natural sounds included trees rustling, sea waves, stream sounds, birdsongs, fountain sounds, frogs croaking, rain and cicadas chirping. The urban sounds included singing, bells ringing, traffic noise, footsteps, construction sounds, human voices, children frolicking and music. The sound stimuli were collected from multiple databases and supplemented by recordings made by the researchers. These recordings were made in classrooms and urban parks in Tianjin during March to July 2017, and a series of 30s sound stimuli were recorded using a Sony PCM-D50 audio recorder. All the sound stimuli were stored in uncompressed wave digital format and converted into the same sample rate and size of 44.1 kHz 16 bit. In addition, according to previous studies, 55dBA was considered the most appropriate sound level by participants because at that level they could hear the sound stimuli clearly but did not feel annoyed by it (Ma & Shu, 2018). Therefore, the sound level of all the sound stimuli was set at 55 dBA, and the duration of each sound was set at 2 min which was thought to be appropriate to complete the experiment tasks by children according to the preliminary experiment. The sound stimuli were played back by a computer through headphones (AKG K702) in the experiment. Some studies have found that audio-visual interaction plays an 73
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Fig. 1. Two simulated environments: school classrooms (left) and urban parks (right).
important role in environmental perceptions (Preis, Kociński, HafkeDys, & Wrzosek, 2015). Moreover, the sounds' meaning within context is an important element in the perceivers' assessment (Payne, Davies, & Adams, 2009). Therefore, the visual contexts of the environmental sounds were also considered in this study. This study was carried out in two simulated visual contexts: school classrooms and urban parks, and a preliminary test was conducted to select the pictures of those two contexts. Ten pictures of classrooms and urban parks taken in Tianjin were rated by children in terms of representativeness of the place. The picture that obtained the highest scores was used to help children visualize the context referred to in the questionnaire (Fig. 1). Classrooms and urban parks were selected for the following reasons. First, they were the most accessible places and most frequently visited by children in China. Second, they were representative of environments with different functions. School classrooms are typical built environments for children's study and development, while urban parks are typical natural environments for children's amusement and relaxation in urban areas. The pictures were shown on a large 46-inch screen, which was placed in front of the participants at a distance of approximately 100 cm.
Table 1 Perceived Restorativeness Sound Scale items grouped by Attention Restoration Theory. Fascination 1. I find this sound appealing. 2. I find this sound interesting. 3. This sound makes me want to hear more. 4. This sound makes me imagine. 5. I am immersed in this sound. Being away 6. I rarely hear this special sound. 7. This is a different sound from what I usually hear. 8. When I hear this sound here, I like to do something different than I usually do. 9. When I hear this sound here, I feel free from study and homework. 10. When I hear this sound here, I feel free from stress and annoyance. 11. Listening to this sound here offers me a period of relaxation. Compatibility 12. This sound environment fits with my personal preferences. 13. I will soon get used to hearing this sound here. 14. This sound environment relates to activities I like to do. Coherence 15. The sound I am hearing belongs here (with the place shown). 16. The sound I am hearing seems quite harmonious with this place.
2.3. Measurements To assess the restorative potential of environmental sounds, the PRSS (Payne, 2013) was employed and revised in relation to a specific environmental sound rather than the whole soundscape. In addition, as the participants in this study were children, the PRSS was also revised according to the Perceived Restorative Components Scale for Children developed by Bagot et al. (2007). Then the revised Perceived Restorative Sound Scale for children (PRSS-C) was translated from English to Chinese by two authors and back-translated by a fluent speaker of both languages. A high similarity between the English and Chinese translations was found. Finally, the questionnaire was pre-tested with five children to ensure that children could comprehend the items easily and accurately. The final 16-item PRSS-C consisted of four components according to ART: fascination, being away, compatibility and coherence. Fascination was measured by five items; Being away was measured by six items; Compatibility was measured by three items; and Coherence was measured by two items (Table 1). Each item was assessed on a 5-point scale (0 = Not at all, 1 = Slightly, 2 = Moderately, 3 = Very, 4 = Extremely). These were converted in the process of analyses from 1 = low restorativeness to 5 = high restorativeness. In addition, the questionnaire also included children's personal information, such as gender and age.
Fig. 2. Photo of a semi-anechoic chamber with two participants performing the experiment.
from outside sounds and ensure that the sound environment is kept constant. Participants were accompanied by their parents who waited in a room outside the chamber during the experiment. Participants took part in the experiment two at a time, supervised by a researcher (Fig. 2). During the experiment, each participant was first asked to imagine a scenario to induce his or her emotional stress and attention fatigue, which was proven to be an effective method to raise stress and fatigue levels (Staats, Kieviet, & Hartig, 2003). Since the experiment was conducted when children had just finished their final exams and began their summer holiday, the text was slightly revised according to
2.4. Procedure The experiment was performed in mid-2017 (July to September) in a semi-anechoic chamber in Tianjin University, which is commonly used for acoustics and equipped with sound absorbing wedges to provide a free field condition with low background noise (20-25dBA). Such chambers can be used as an ideal listening room to avoid disturbance 74
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Fig. 3. Diagram of experimental procedure.
children's actual conditions. Researchers read the text as follows: ‘This semester, you have studied very hard. Now, at the end of the final exams, you have been asked to do a lot of homework. You have difficulty concentrating, and you are very anxious because of concerns about test scores’. Then, the audio-visual stimuli were presented, and participants were asked to imagine that they were actually in the midst of the present setting. After exposure to each audio-visual stimulus for 10s without doing anything, children were asked to circle the answer on each PRSS-C item while the audio-visual stimulus was continuously displayed. The time for completing the questionnaire was adjusted according to each participant's individual needs, and there was a 10s interval to refresh before exposure to the next audio-visual stimuli. Each stimulus took about 2 min to be evaluated (Fig. 3). A total of 32 audio-visual stimuli (2 visual × 16 sound stimuli) were presented and evaluated by each participant. Half of the children were first exposed to the photo of classrooms and then urban parks, while the order was reversed for the others. In addition, the 16 sound stimuli were counterbalanced in random order to minimize order effects. Furthermore, the whole procedure was divided into three parts of 20min each with two periods of 15-min rest between them to avoid fatigue and impatience (about 90 min totally). Finally, participants completed the basic sociodemographic data. The whole procedure was pre-tested before the formal experiments to ensure that it was appropriate for an 8–12 age group.
collected data of all environmental sounds. The Kaiser-Meyer-Olkin index (0.909) and Bartlett's test of sphericity ( χ 2 =15152.78, p < .001) indicated the adequacy of the sample size for conducting a factor analysis. Given the convergence of the scree plot and Kaiser's criterion (eigenvalues are greater than 1), results showed that three underlying factors were extracted from 16 items (Table 2). Factor 1 (40.06%) consisted of 11 items; factor 2 (20.41%) included three items; and factor 3 (11.75%) consisted of two items. The three factors covered 72.21% of the total variance, and Cronbach's alpha was above 0.80 for each factor. The correlations between the three factors and each item with the high-correlation data (above 0.5) were highlighted. To examine whether there was a difference in restorative qualities between natural sounds and urban sounds, factor analysis was then conducted twice based on the data of natural sounds and urban sounds, respectively. Similar results were obtained in both contexts. This indicated that the three-factor structure was suitable for all kinds of environmental sounds to a certain extent. Overall, there were three restorative qualities of environmental sounds as perceived by children, and they could be interpreted as attractiveness, compatibility and coherence, respectively. 3.2. The potential restorative sounds perceived by children The restorative values of the eight natural sounds and eight urban sounds evaluated by the children were first compared using non-parametric Mann-Whitney U tests, given the non-normality of the raw data distribution. The results showed that natural sounds were perceived as more restorative than urban sounds (p < .001 for attractiveness; p < .01 for compatibility; p < .05 for coherence). However, some urban sounds were perceived to be more restorative than most natural sounds, such as music, singing, and bells ringing (Fig. 4). Therefore, merely dividing the environmental sounds into natural and urban was not appropriate. The environmental sounds should be further classified in different contexts based on their perceived restorative qualities. With the three restorative qualities, 16 environmental sounds were clustered using hierarchical cluster analysis (Fig. 5). Based on squared Euclidean distances among the sounds, four categories were created in both classrooms and urban parks. In classrooms, most natural sounds were clustered in category 1, while urban sounds were divided into categories 2 (music-like sounds), 3 (human voices), and 4 (artificial sounds). In urban parks, natural sounds were divided into categories 1 (general natural sounds) and 3 (animal sounds), while urban sounds were divided into categories 2 (music-like sounds) and 4 (general urban sounds). When comparing the classification of sounds in those two contexts, it could be seen that urban sounds were further classified in classrooms and natural sounds were further classified in parks. In addition, it was also interesting to note that category 2 in these two contexts consisted of the same sounds (i.e. singing and music), which indicated that the restorative qualities of music-like sounds have no difference between contexts, at least for children. The perceived restorative qualities of different sound categories were further compared (Fig. 6). As the mean values of environmental sounds were normally distributed, Bonferroni post-hoc comparisons
2.5. Statistical analysis Statistical analysis was performed with SPSS 22.0. Specifically, a factor analysis was used to investigate the restorative qualities of environmental sounds as perceived by children. In particular, principal component method (a factor-extraction procedure) and variance maximization (i.e. Varimax, an orthogonal rotational strategy) were chosen during the factor analysis (Fabrigar, Wegener, MacCallum, & Strahan, 1999) to identify the underlying common factors of 16 correlated variables in PRSS-C. In addition, to explore the potential restorative sounds as perceived by children in different contexts, a hierarchical cluster analysis was performed among the 16 environmental sounds based on Ward's method algorithm (Murtagh & Legendre, 2014). A Bonferroni post-hoc test, which is recommended as a relatively conservative test to compensate for spurious significant results that occur with multiple comparisons, was conducted to further compare the perceived restorative qualities of each sound category. Finally, a nonparametric Spearman rank correlation matrix was created to investigate the relationship between psychoacoustic parameters and perceived restorative values, and non-parametric tests (Mann-Whitney U-tests and Kruskal-Wallis tests) were used to explore the influence of personal attributes and contexts on children's perceptions. 3. Results 3.1. The restorative qualities of environmental sounds perceived by children A factor analysis was conducted to investigate the restorative qualities of environmental sounds as perceived by children, using the 75
Journal of Environmental Psychology 60 (2018) 72–80
.18 .15 .14 .92 .91 .18
.34 .24 .34 .31 .33 -.21 -.13 .28 .39 .43 .43 .87 .88 .81 .15 .17 .77 .78 .79 .69 .74 .74 .79 .66 .72 .75 .73 .18 .18 .35
.17
.11
.73 .69 .75 .57 .67 .60 .66 .52 .67 .75 .72 .81 .82 .80 .88 .88
were conducted. With regard to school classrooms, music-like sounds (category 2) were shown to be the most restorative sounds in terms of attractiveness and compatibility, followed by generally natural sounds (category 1). Human voice (category 3) showed the highest values of coherence, whereas artificial sounds (category 4) showed the lowest restorative values in all three qualities. With regard to urban parks, both music-like sounds (category 2) and animal sounds (category 3) showed the highest restorative values. However, animal sounds showed a higher value of coherence than music-like sounds. General natural sounds (category 1) were moderate in the three restorative qualities followed by general urban sounds (category 4). It was notable that the values of the three restorative qualities were quite different from one another in both contexts. The values of compatibility were generally higher than the values of attractiveness and coherence. However, the values of coherence were the highest for the environmental sounds of category 3. This means that the coherence of sound and context was the most important restorative quality for category 3 in both contexts. Moreover, to investigate the restorative values of each environmental sound, the 16 sound samples were plotted into two-dimensional coordinate systems (Fig. 7). In classrooms, music and singing were perceived by children as the most restorative sounds, while construction sounds and traffic noise were perceived as the least restorative sounds. In addition, music was the most attractive and compatible sound, and children frolicking was the most coherent sound. In urban parks, music and singing were also perceived by children as the most restorative sounds, while most urban sounds, such as construction sound, were perceived as the least restorative sounds. Similar to classrooms, music was also the most attractive and compatible sound. However, natural sounds (i.e. birdsong and cicadas chirping) were most coherent with the environment of urban parks.
.19 .13 .93 .94
3.3. The factors influencing the restorative qualities of environmental sounds
.11
.80 .81 .80 .69 .71 .75 .78 .74 .77 .76 .70 .20 .16 .35
.24 .29 .32 .36 .89 .90 .83 .15 .16
.15 .19
.11 .17 .11 .23 .22 .22 .33 .34 -.11
.70 .73 .71 .59 .62 .58 .60 .61 .69 .70 .66 .84 .88 .83 .90 .92
3 (12.14%) 2 (19.36%)
To identify the acoustic characteristics of the environmental sounds that contributed to the children's restorative perceptions, five psychoacoustic parameters—loudness, fluctuation strength, sharpness, roughness, and tonality—were analysed for each sound. Loudness is defined as the magnitude of an auditory sensation. Fluctuation strength is the sensation with slower changes in sound. Sharpness is caused by high-frequency components in sound. Roughness is related to the beating phenomenon, or relatively quick changes of sound. Tonality indicates whether sound consists mainly of tonal components or broadband noise (Zwicker & Fastl, 2013). For each sound, the five parameters were calculated by ArtemiS software (HEAD acoustics) in terms of the mean values over 30s, as reported in Table 3. The relationship between the three restorative qualities and five psychoacoustic parameters showed that the perceived restorative values of environmental sounds were positively correlated with fluctuation strength and sharpness to some extent, but negatively correlated with loudness and roughness. However, the three qualities had no correlations with tonality. In addition, the influence of children's personal information (i.e. age and gender) and the contexts on their restorative perceptions were analysed (Table 4). The results showed the children's perceptions of attractiveness and compatibility were significantly different between genders. Similarly, there was also a significant difference between age groups in terms of attractiveness, compatibility and coherence. Moreover, contexts only had a significant effect on the perception of coherence.
.14
.27 .35 .39 .40 .87 .89 .82 .15 .17 Coherence
Compatibility
Being away
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Fascination
Items with the high-correlation data (above 0.5) are indicated with a bold front.
.12 .14 .17 .14 .93 .92
.71 .71 .73 .59 .65 .60 .63 .57 .68 .73 .69 .82 .85 .81 .90 .90 .30 .24 .29 .32 .34 -.16
.78 .79 .80 .69 .72 .76 .79 .70 .75 .75 .72 .19 .17 .36
.11 .16
Communalities 3 (11.75%) 2 (20.41%) 1 (40.06%)
Overall sounds PRSS-C Items Restorative qualities in ART
Table 2 Factor analysis of overall sounds, natural sounds, and urban sounds.
.11 .16
2 (21.22%) 1 (39.30%) 1 (40.56%)
Communalities
Urban sounds Natural sounds
3 (11.57%)
Communalities
S. Shu, H. Ma
4. Discussion The first aim of this study was to investigate the restorative qualities of environmental sounds as perceived by children. The results showed 76
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Fig. 4. Perceived restorative values of each environmental sound.
Fig. 5. Dendrogram for 16 environmental sounds by hierarchical cluster analysis (Left: School classrooms; Right: Urban parks).
Fig. 6. Perceived restorative values of different sound categories in school classrooms (Category 1: natural sounds; Category 2: music-like sounds; Category 3: human voice; Category 4: artificial sounds) and urban parks (Category 1: general natural sounds; Category 2: music-like sounds; Category 3: animal sounds; Category 4: general urban sounds).
different with extent for visual environments, as coherence in this study indicated the coherent interrelationship between environmental sounds and their visual contexts. Overall, it is likely that people's restorative perceptions of visual environments are more complicated. A possible reason is that visual environments vary in terms of the number and type of visual elements compared to the specific sound sources used in this study. Second, this study revealed the possibility of a difference between children and adults in the perceptions of environmental sounds, as compared with the study of Payne (2013). However, this finding should be confirmed by future studies with a larger sample size. Based on the three restorative qualities above, we also found that
that for children, three subjective qualities were required for a restorative sound, including attractiveness, compatibility, and coherence. This result was quite different from the restorative qualities of visual environments and acoustic environments as perceived by adults. First, the number of restorative qualities of environmental sounds in this study was fewer than those of visual environments (i.e. fascination, being away, compatibility, and extent) (Laumann, GÄRling, & Stormark, 2001). Fascination and being away were merged into attractiveness for sounds, which represented the inherent qualities of sounds to allow attentional recovery and emotional relaxation. Additionally, the meaning of coherence for environmental sounds was also 77
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Fig. 7. Restorative qualities of each environmental sound in school classrooms (Category 1: natural sounds; Category 2: music-like sounds; Category 3: human voice; Category 4: artificial sounds) and urban parks (Category 1: general natural sounds; Category 2: music-like sounds; Category 3: animal sounds; Category 4: general urban sounds).
potential restorative sounds perceived by children were quite consistent with those in classrooms. However, the most coherent environmental sounds were quite different between the two contexts. Compared to the most coherent sounds (i.e. human voices and children frolicking) in classrooms, natural sounds (i.e. birdsong and cicadas chirping) not only showed the highest coherence in urban parks, but also showed a great quality of attractiveness and compatibility. Therefore, it might be possible to achieve actual restorative effects on children when they were exposed to birdsong and cicadas chirping in urban parks. In addition, the coherence of environmental sounds was found to vary significantly in different contexts. This finding confirmed the importance of audio-visual coherence in environmental perceptions,
the restorative sounds for children were somewhat different than those for adults, especially in the context of built environments. For children, urban sounds such as singing and music were perceived as the most restorative sounds in classrooms, while adults usually prefer natural sounds in built environments (Yu, Behm, Bill, & Kang, 2017). Certainly, for children, natural sounds are still perceived to be more restorative than most common urban sounds. Therefore, music, singing, and most natural sounds might be considered as potential restorative sounds in school classrooms, while other urban sounds should be reduced as much as possible. In particular, the sounds of human voices and children frolicking should be controlled properly because these are the most coherent sounds and inevitable in classrooms. In urban parks, the 78
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Table 3 Mean values of psychoacoustics characteristics of 16 environmental sounds.
Mean values Singing Trees rustling Bell ringing Sea waves Traffic noise Footsteps Stream sound Birdsong Fountain sound Construction sound Human voice Frogs croaking Children frolicking Music Raining Cicadas chirping
Loudness (sone GF)
Fluctuation strength (vacil)
Sharpness (acum)
Roughness (asper)
Tonality (tu)
10.70 11.80 4.96 12.30 15.30 10.00 7.21 4.33 7.99 5.42 10.20 3.19 9.12 8.67 7.52 6.29
0.0228 0.0063 0.0128 0.0050 0.0104 0.0542 0.0304 0.0542 0.0042 0.0277 0.0354 0.0081 0.0197 0.0547 0.0046 0.0027
1.11 1.64 3.47 1.66 1.33 1.72 1.76 1.86 1.96 1.45 1.14 1.78 1.47 1.04 1.98 2.37
0.85 1.67 0.24 1.60 1.46 2.27 2.25 0.15 1.63 1.12 1.29 0.39 1.32 0.78 1.51 0.50
0.6320 0.0390 0.4750 0.0216 0.0594 0.0182 0.0076 0.0126 0.0262 0.0451 0.0888 0.0279 0.1570 0.7080 0.0227 0.0326
.08** .05 .06
.06* .01 .06*
−.19** −.10** −.19**
-.01 .00 .02
Spearman's correlation coefficients Attractiveness −.14** Compatibility −.06 Coherence −.14**
Significant correlations with ** as p < .01 and * as p < .05.
experience. This is because we were less interested in the acoustic characteristics of environmental sounds than the restorative perceptions they produce. Certainly, many acoustic parameters have the potential to affect children's restorative perceptions. From the standpoint of intervention, we believe that if we better understand which acoustic parameters most affect children's restorative perceptions of sounds, it will be easier to decide which particular sound needs to be considered in the environmental design. Therefore, future research is necessary to determine how other acoustic parameters contribute to the perceived restorativeness of environmental sounds. Moreover, future research is also required to show whether the findings are generalizable to other environmental sounds and more children.
Table 4 The influence of children's gender, age, and contexts on sounds' restorative qualities.
Attractiveness Compatibility Coherence
Gender
Age
Context
.00** .00** .94
.00** .00** .03*
.42 .47 .00**
Significant difference with ** as p < .01 and * as p < .05.
which was in accordance with many previous studies (Ma & Shu, 2018). We also found significant correlations between children's restorative perceptions and sounds' fluctuation strength, sharpness, loudness, and roughness. This indicated that the restorative potential of environmental sounds could be predicted using their psychoacoustic parameters to a certain extent. Although further examinations with more sound samples are still needed, this study enriches existing research and allows for further exploration of the mechanism behind the influence of psychoacoustic parameters on the restorativeness of sounds. Finally, children's restorative perceptions of environmental sounds were also found to be significantly influenced by their gender and age. Therefore, the future design of children's acoustic environment should consider children's individual characteristics. Despite the contributions described above, there are a few limitations that should be noted when interpreting the results. First, this is a laboratory study using photographs to simulate contexts of school classrooms and urban parks. Therefore, the sense of immersion might be quite poor. Nevertheless, by controlling variables in a laboratory setting, this study confirmed the perceived restorative qualities of sounds in a strict causal sense. Second, this study focused on children's perceptions of restorative qualities instead of examining their actual restoration. Although the results are in line with previous studies highlighting the experienced restoration of environmental sounds, further work is needed to establish that such sounds will reduce stress or fatigue. Recent studies have shown that adults' restorative experience of a soundscape is related to their physiological response (Alvarsson et al., 2010; Medvedev, Shepherd, & Hautus, 2015). Therefore, we believe that this study lays a foundation for future research, which will examine the actual restorative effects of environmental sounds on children. Third, this study only investigated the influence of a few psychoacoustic parameters on the restorative
5. Conclusion Based on the children's subjective evaluation, three key restorative qualities were revealed for a potential restorative sound, which were interpreted as attractiveness, compatibility, and coherence. Based on the three restorative qualities, environmental sounds were subdivided into four categories each in the context of school classrooms and urban parks. For both contexts, music-like sounds, such as singing and music, were perceived to be the most attractive and compatible sounds, followed by general natural sounds. However, the most coherent sounds were different in the two contexts. Furthermore, the perceived restorative values of environmental sounds were found to be significantly influenced by their psychoacoustic parameters, children's personal information, and visual contexts. Therefore, it is important to consider designing restorative soundscapes to improve the restorative experience in children's living environments.
Acknowledgements This work was supported by the National Natural Science Foundation of China [Project No. 51478303, 51678401].
Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.jenvp.2018.10.011. 79
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