SOUND PERCEPTION PARAMETERS IN URBAN PUBLIC SPACES

Transcription

1 SOUND PERCEPTION PARAMETERS IN URBAN PUBLIC SPACES S. Marry, M. Baulac Université Paris Est, CSTB (Centre Scientifique et Technique du Bâtiment), 24 avenue Joseph Fourier Saint Martin d Hères, France {solene.marry, marine.baulac}@cstb.fr Abstract Sound perception in urban public spaces, a current issue in urban planning, is of interest in this study. The research is based on a qualitative survey conducted among thirty people, who were selected along variables such as their place of residence or their mode of transport. Three groups of ten people were asked to rate three urban squares during two seasons. The inquest is based on 180 questionnaires and 18 focus groups performed in situ, followed by 30 individual in-depth interviews, including cognitive map tests. Results from the investigation are correlated with acoustic measurements at both seasons. This allows us to determine some parameter classes (temporal, spatial, sensitive and individual) which influence the perception of the environmental sounds. The potential uses of these results by urban planners for improving the quality of urban places are then discussed. Keywords: sound perception, public spaces, qualitative survey, environmental sounds 1 Introduction Research in acoustics indicates that many parameters influence the sound perception in urban environment. E. Lecourt reminds us of the differences between individuals when defining silence [1]. To speak about environmental sound amounts to a tautology and emphasizes how behind the sonic field is, in current ideology. Some researchers have shown some individual parameters such as age, gender, economical status or subjective sensibility link to noise [2]. Discomfort concept is often studied in environmental sound research as in references [3], [4], or [5]. Few research laboratories such as Cresson take an interest in ordinary sound ambiances and everyday sounds. Some multidisciplinary attempts try to connect physical and perceptive approaches [6]. Our study is based on a survey conducted in order to be acquainted with ordinary sound public space, perceptive parameters and to contribute to define urban ambiances. Our hypotheses are: public space sound perception parameters are numerous and heterogeneous; spatial, temporal, sensorial, individual 1

2 parameters and spatial practices impact sound perception; space planning in urban public space is fundamental not only for acoustics but also for synesthesical perception. 2 Methodology 2.1 Methodological protocol The aim of this research is to determine sound perceptive parameters in public spaces. Methodology is based on a qualitative survey and acoustic measurements in order to correlate perceptive and physical data. A preliminary test allowed us to develop the questionnaire and to confirm the field of study. The survey was conducted along six months from September 2009 to March This qualitative survey is constituted by two different parts: the on site part was executed at two seasons with the same participants and a second part was achieved then and concerned individual interviews. The first part of the methodology is constituted by 180 on site questionnaires (each participant answered the questionnaire at each season and on each square), 540 pictures (interviewees were asked to take three photographs on each square at both seasons representing the global ambiance), 18 on site focus groups (participants discussed together their feeling and appraisal on the square). This first collective part of the methodological protocol is associated with 30 individual in-depth interviews, with the same participants. These individual interviews included: - in depth interviews about notably their memory of the three squares (ambiance, comfort, environmental sounds) and their urban practices, - a commentary of the pictures taken on the squares, - five cognitive map tests (participant were asked to draw the sound environment of the three squares, the ideal sound ambiance of a public square and the worst sound ambiance of a public square), - rank urban typologies in association with quality environmental sounds Field of study Figure 1 - Squares: central urban public spaces in urban landscape [7] 2

3 For this research, the field of study is made up of three urban public squares. A square is a particular public space typology, which is at the base of public space concept (Greek agora), see Figure 1. Also, a square has a clear spatial delimitation and strong mental representations. Figure 2 - Place Centrale, campus, Saint-Martin-d Hères (cadastre.gouv.fr) Figure 3 - Place Mistral-Eaux-Claires, urban regeneration zone, Grenoble (l AUC, J. Kopp) Figure 4 - Place des Tilleuls, historical urban center, Grenoble (cadastre.gouv.fr) 3

4 We wondered if spatial morphology and urban typology influenced sound perception. To check on this hypothesis, we chose three different types of squares (size, form, gap ): figures 2, 3, 4. Their localizations in the urban area (central position or not) were also a choice criterion as district type, vegetation or water presence Cross-section constitution Thirty interviewees were selected using variables: age, gender, place of residence and means of transportation. A remuneration was attributed to all interviewees at the end of the three survey meetings to motivate to finish because it was important in our protocol that the same interviewees completed the survey In site survey Qualitative survey Three groups of ten people (the first group is composed by people who live in houses, the second one by people who live in old collective housing and the third one by people who live in recent collective housing) were asked to rate these urban squares during two seasons. In this part of the survey, performed in situ, interviewees were asked to: - answer individually a questionnaire, - take individually three photographs (describing the ambiance) - group together to discuss in a focus group their perception of the place. Figure 5 - Focus group in September 2009, Place des Tilleuls, group B Acoustic measurements Acoustic measurements were acheived during the same seasons that the survey was conducted and on the same day of the week in order to compare the same urban temporalities. The global aim is to compare acoustics levels and types of environmental sounds to sound perception. This is why equivalent - one second - acoustic level is measured on each square, on fixed points and while travelling around the square writing down sonic events. Measurements were not done as the same time as the qualitative survey in order not to interfere with interviewees answers. 4

5 2.1.4 Individual in-depth interviews After the on site survey, we saw all interviewees again individually for an in-depth interview for around one and a half hours. They were asked to speak about their memory of the squares, to explain why they took these pictures to show the place ambiance and then to do five cognitive map tests. Cognitive map tests concern the sonic environment of the three squares, the ideal sonic ambiance and the worse sonic ambiance of a square in general. And finally, we showed to the interviewees seven urban morphologies and they were asked to rank these morphologies from the most pleasant sonic environment to the most unpleasant one. 3 Qualitative on site survey results In this section we will discuss a few preliminary results but work is still in progress. 3.1 Results The results concern words used by all thirty interviewees to describe the general ambiance of Place Centrale (Figure 6), Place Mistral-Eaux-Claires (Figure 7) and Place des Tilleuls (Figure 8). These words used by participants to describe the squares had been bringing together in few themes as nature or noisy September December Figure 6 - Words named by 30 interviewees to define the general ambiance of Place Centrale at two seasons 5

6 September December Figure 7 - Words named by 30 interviewees to define the general ambiance of Place Mistral- Eaux-Claires at two seasons September December Figure 8 - Words named by 30 interviewees to define the general ambiance of Place des Tilleuls at two seasons 3.2 Analysis : Words used to define three squares ambiances In the on site questionnaire interviewees were asked to qualify the global ambiance of the area. We can emphasize that sound ambiance is used to describe global ambiance in an urban public space, in Place Centrale and Place des Tilleuls (Figures 5 and 7) it is particularly in evidence. Another observation concerns temporality; interviewees describe ambiance with more sound words during the second in site questionnaire. We can venture the hypothesis that during the second time, in December, the three squares are well known and it is for this reason that attention is more on sounds. For instance in Place Mistral-Eaux- Claires (Figure 5), the word noisy is used by two interviewees in September to describe the ambiance and 8 of them used it in December. 6

7 N. Rémy [8] notices that memory is predominant in everyday sounds perception. Space knowledge seems to interfere in global perception and particularly in sonic perception. That is why we chose interviewees who did not previously know the squares. We wondered if their sonic space judgment would change between the two experiments. These three figures (Figures 5, 6 and 7) illustrate the perceptive change between two periods. 4 Individual in-depth interviews results In-depth interviews, realized with all on site participants, complete the perceptive survey with representative data. We wondered if place of residence (when it is a choice) influences sonic environment representations associated to urban typologies. In order to gain understanding of urban environmental sound representations, seven urban typologies were shown to interviewees who must rank them in accordance with quality environmental sounds. We discuss here some preliminary results. 4.1 Urban typologies appraisal A survey, conducted in 2007 asked over 1000 French participants to associate housing types to different words. The word calm is associated to an isolated individual house by 80% of participants [9]. During the in-depth interview in our survey, all thirty participants were asked to rank seven urban typologies from 1 to 7, 1 corresponding to the most pleasant sonic environment and 7 to the most unpleasant sonic environment. In first place, which is shown in figure 8, isolated individual house is clearly associated to a pleasant sonic environment. On the contrary, collective housing areas and Haussmannien housing are most often associated to the worst sonic environment. We can highlight an unexpected result: a collective urban typology (in this case city medium collective housing), is ranked as a more pleasant sonic area than an individual typology (private housing estate). This may draw a parallel between urban typology (pavillons) which have a bad reputation and sonic appraisal associated with them. collective housing areas Haussmannien housing big buildings private housing estate (pavillons) city medium collective housing city small individual housing isolated individual house Figure 9 - Sonic environment associated to urban typologies (1: More pleasant, 7: more unpleasant) 7

8 people INTERNOISE 2010 JUNE LISBON PORTUGAL 4.2 Influence of type of residence We wondered if the type of residence influences sonic representation concerning various urban typologies. When we showed to participants an isolated individual house, participants living in an individual house associated this typology to a pleasant sonic environment, more than other participants.90% participants living in individual houses rank this typology in the three more pleasant sonic environments. Figure 10 shows differences between residential parameters. This experiment shows that a link can be assumed between housing type, urban typology representations and sonic environment representations Group A Individual house Group B Old collective housing Group C Recent collective housing Rank Figure 10 - Sonic environment associated to isolated individual house (Left: most pleasant, right: most unpleasant) 5 Conclusions To conclude, our study, based on a qualitative survey, tries to understand everyday sounds perception in urban public spaces. We wondered which parameters influenced sound perception. This evaluation could be used by urban planners in order to design urban public spaces as public squares. Sound perception should be considered as a significant aspect in urban public space appraisal and may alter city planning and urban furniture design. 8

9 Acknowledgments I would like to thank all interviewees who took part in this survey and participate in interviews and particularly on site interviews in all weathers. References [1] Lecourt E. Au sortir du bruit. Le journal des psychologues, Vol 261, 2008, pp [2] Belojevic G, Jakovljevic B. Subjective reactions to traffic noise with regard to some personality traits. Environment International. Vol 23 (2), 1997, pp [3] Champelovier P, Cremezi-Charlet C, Lambert J. Evaluation de la gêne due à l'exposition combinée aux bruits routiers et ferroviaires, 2003, 150 p. [4] Fyhri A, Klaeboe R. Direct, indirect influences of income on road traffic noise annoyance. Journal of environmental psychology, Vol 26, 2006, pp [5] Sandreock S, Griefahn B, Kaczmarek T, et al. Experimental studies on annoyance caused by noises from trams and buses. Journal of Sound and Vibration, Vol 313, 2008, pp [6] Raimbault M, Lavandier C. Comparaison de facteurs perceptifs et de paramètres physiques pour l'interprétation d'ambiances sonores urbaines. Actes du 6ème CFA. Lille, 2002, pp [7] Bertrand M, Listowski H. Les places dans la ville. Dunod.; 1984:92 p. [8] Rémy N. Sound quality in railstation: users' perceptions and predictability. Dans: Proceedings of the 29th International Congress in Noise Control Engineering.Vol 3. Nice, France: SFA, INRETS, 2000, pp [9] Les français et leur habitat : perception de la densité et des formes d habitat. Société française d enquêtes par sondage, Paris, Sofres, 2007, 25 p. 9