a cross-cultural - Webistem

Urban sound environment quality through a physical and perceptive classification of sound sources: a cross-cultural study F. Guyot, C. Nathanail, F. Montignies, B. Masson LAPS design, 75010 Paris, 54 rue René Boulanger, France, [email protected]

The aim of this research is to establish a global methodology in order to create a data base of sound sources present in our urban environments, and in this way, better understand the perception of urban noise by assessing the role of each source in the global quality of the environment. The relevant work is undertaken in two European countries culturally different: France and Greece. In creating this data base, we wish to upgrade the existing data bases and to obtain a classification of the sources, we also want to improve and democratise noise maps by inserting, on one hand perception parameters related to sound sources, and on the other corresponding soundscape recordings. The methodology is mainly based on the physical description of urban spaces (architectural and acoustical) and of sound sources, and also on the perceptive evaluation of principal sources. This evaluation is obtained through linguistic descriptions and field surveys with different local urban actors. The work is divided in four main steps: the choice of equivalent sites in both countries and their description, the identification and the description of sources, the field surveys and finally, the corresponding psycholinguistic analyses and the correlations. (This work is supported by the French Ministry of Ecology and Sustainable Development through the research program ‘Bruit et Nuisances Sonores’).

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Introduction composing this environment and this is even more true for urban contexts where a multitude of different sound sources coexist and may interact.

It is today generally admitted that global sound level is not sufficient to evaluate environmental noise annoyance and it is obviously even less sufficient to evaluate sound environment quality. This is largely because the nature and the meaning of the sound sources composing this environment can also play an important role.

In 1977, the composer Schafer [8] introduced the notion of soundscape together with a first classification of sound sources. According to him, three main characteristics define a soundscape: the tonality, the signal (emerging sound sources) and the sound print. Schafer, based on literature, anthropological and historical references, proposed a classification of the sound sources according to criteria related to the function and the meaning of the sounds.

Indeed, in a pilot study, Fields [1] showed that at constant sound level, trains are perceived as less annoying than oad vehicles, and that road vehicles are less annoying than aeroplanes. In another work, it has been observed that an object producing a high sound level can be judged more positively than another one at lower level, the sound level in this case is perceived as an indicator of efficiency [2]. In a review work grouping together 33 studies from 10 countries and dealing with 9 different types of noise, it was observed that individual noise exposure typically explains less than 20% of the variance in reaction and that factors like attitude to the noise source, fear or danger related to it, can account for more variation in reaction than noise level [3, 4]. Also, different groups of people can react in different ways: the evaluation of sound quality and of sound sources can therefore depend on sociocultural, contextual or individual particularities. This was already observed in 1975 in studies concerning neighbourhood noise [5] and in several works since then [ 6, 7]. We consider therefore that in any attempt of qualitative evaluation of the urban sound environment, it is essential to take into account the sound sources

Guastavino [6] distinguished 3 main categories of sounds defined by the degree of human presence into the sounds: sounds related directly to human presence (voices, steps, etc), sounds related indirectly to human presence (vehicles, music, etc.) and sounds not related to human at all (sounds of the nature). Another work realised by Leobon [9] developed an interesting method for evaluating soundscapes in terms of both quantitative and qualitative criteria (sound levels and sound sources respectively). An experimenter analysed qualitatively short sound recordings. This approach is based on the structuralistic hypothesis that every sound phenomenon can be decomposed in a series of simple identifiable and classifiable elements, the sound events. He obtained lists of sounds which after classification he represented graphically on maps. He proposed six categories of sounds: background noise, mechanical activity (traffic,

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Forum Acusticum 2005 Budapest

Guyot, Nathanail, Montignies, Masson

works, etc.), sounds of animals and nature (birds singing, etc.), human presence (steps, voices, etc.), human activity (noises of shops, activities, etc.), language and communication (intelligible conversations, musical representations, etc.).

each country were chosen to belong to the same area in order to respect a certain urban and sociocultural uniformity. The three typical urban environments chosen were: 1. Pedestrian roads, where human activity dominates compared to traffic : Komninon street in Kalamaria and Montorgueil street in Paris (abbreviated ‘ped-Gr’ and ‘ped-Fr’ respectively). 2. Narrow one-way streets, where human activity and traffic coexist more or less in equivalent levels: Passalidi street in Kalamaria and Montmartre street in Paris (abbreviated ‘ow-Gr’ and ‘ow-Fr’). 3. Avenues, where traffic tends to dominate the sound environment but still commercial activity exists: Pontou street in Kalamaria and Etienne Marcel street in Paris (abbreviated ‘ave-Gr’ and ‘ave-Fr’).

In the legislative context and related to these scientific considerations, the application of the new European Directive on environmental noise (n°2002/49/CE) aims to the assessment and management of environmental noise in Europe and to the harmonisation of the noise strategies between countries. It introduces a new sound level metric (Lden) in order to assess annoyance, but encourages the investigation of complementary indicators which would help to better assess and communicate reactions to noise and facilitate comparisons between sites or countries. The present work has two main objectives: first, develop a method to assess quantitatively and qualitatively the sound sources present in our urban environments and second, evaluate their role in the global appreciation of the sound environment. It is attempted to relate the presence of these sources and their qualitative evaluation to the type of the urban structure and to the type of exercised activities. Also, this work aims to relate the qualitative evaluation of certain sources to their objective description (occurrence, acoustic properties, etc.) and to create a data base of urban sound sources together with their description. Unlike Leobon whose results on sources were obtained on a purely subjective base [9], this work proposes the use of an investigation method based on sociological field studies. In order to better explore the method, to test its robustness across sites but also to study the differences in urban sources and their evaluation between countries, we organised this work in two culturally different countries: Greece and France. Three sites were selected and studied in each country, they are varying on the type of traffic, urban structure and type of exercised activities.

The criteria for their choice were: local activities (uses, density of shops,...), geometry and urban structure (buildings, pavement, vegetation,...), traffic characteristics (load, type of flow, speed, vehicles,...) and acoustical description (type of sources, sound levels). Mean sound levels were measured on short periods (1h) and calculated as LAeq(7h-23h) at 2m height, they are around 60 dB(A) for both pedestrian streets, and around 70 dB(A) for the other two types of sites.

In the following, we present the part of the methodology concerning the choice of the sites and the field surveys. The related results are presented after, separately for the evaluation of the general sound environment and for the assessment of the sound sources. A final discussion presents the first conclusions.

Street interviews were conducted in the three selected sites in each of the two cities. The questionnaire was translated into the two languages and contained a first section concerning urban environment and a second section, concerning sound environment and sound sources. In this second section people were first asked to judge the sound environment of the street openly (open question), then reply on the 5 point verbal scale: very pleasant, pleasant, medium, unpleasant and very unpleasant (closed question). Open and closed questions were used to enable verbal and numerical analyses respectively. Participants were asked next to mention the sound sources that they usually encounter in the particular environment and, again, judge them first openly and then on the same 5 point verbal scale.

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2.2 Field surveys The field approach had to be adopted in order first, to evaluate the part of sound environment in the general street environment, and second, to assess the present sound sources, characteristic of each site. Indeed, laboratory controlled experiments cannot respect the realism and the complexity of an urban environment, and are generally realised with subjects not knowing and not even concerned with the environment under study. Among the methods permitting to have access to long term memory information, we chose the interviews on a predetermined questionnaire, a simple and relatively easy to analyse method.

Methodology

2.1 Choice of sites Three sites have been selected in Greece in the city of Kalamaria (agglomeration of Thessaloniki) and three in France in the second district of Paris. All three sites in

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Results also show that pedestrian sites are more clearly distinguished from the other two types of sites in term of sound environment, they also validate the selection of the corresponding sites in the two countries.

A total of 443 people participated in the surveys, distributed equally among sites (approximately 75 per site). Two thirds of them origin from pedestrians and one third from shop-keepers.

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3.2 Discussion

Evaluation of the environment

Results reveal that for pedestrians the sound environment is related to the evaluation of the global environment and that this relation is stronger in circulated roads where the noise problem actually exists. In fact, when in a pleasant sound environment, people are not concerned with noise. This seems to indicate that acceptable sound environment is mostly a condition of environmental quality and less an enhancing factor of its quality.

The field surveys permitted to evaluate the global urban environment, first as a whole and then in terms of a set of its composing dimensions like the presence of vegetation, the quality of air, the sound environment, the quality of pavements, the transportation facilities, the parking, etc. As one would expect, the global environment of the pedestrian streets is more appreciated than the environment of the two circulated streets, and the environment of the less circulated one-way streets is more appreciated than the environment of the avenues. Correlations observed between the evaluation of the global urban environment and the evaluation of the sound environment are significant and relatively high (between 0,34 and 0,58) in most sites for pedestrians while they are not significant for shop keepers. The correlations obtained for pedestrians seem to increase with the increasing circulated character of the street.

Concerning the sound environment itself, the fact that for both pedestrian roads it is judged more positively than for the other two types of streets (one-way and avenues) can certainly be partly attributed to the 10 dB(A) level difference between sites. The subjective difference, though, observed in both countries, between the one-way roads and the avenues cannot be explained by differences in sound level since all sites have levels of the order of 70 dB(A). This indicates that sound level alone is insufficient to describe the quality of the sound environment and that other factors should be searched.

3.1 Evaluation of sound environment

Concerning the comparison between the two countries, our results seem to invalidate a common belief. In fact, one would expect that in Greece, a Mediterranean country with culturally noisier attitudes, people would be more tolerant to noise. This is not the case, actually Greeks seem as critical toward their sound environment as are people in Paris, a northern city pioneer in public communication on environmental noise problems.

The evaluation of the sound environment on the 5 point verbal scale is presented separately for Kalamaria and Paris in Figure 1. Results are presented grouped over pedestrians and shop-keepers (small differences between types of exercised activity are observed but are not discussed here). %

%

60

60

a)

ped-Gr

50

b) ped-Fr

50

ow-Gr 40

ave-Gr

ow-Fr 40

30

30

20

20

10

10

4

ave-Fr

As mentioned above, in the attempt to assess and classify urban sound sources, as well as to evaluate their contribution in the evaluation of the sound environment, participants were asked to report the sound sources which they usually encounter in each environment and evaluate them.

s

0

0 very pleasant

pleasant

medium

unpleasant

very unpleasant

very pleasant

pleasant

medium

unpleasant

Sound sources

very unpleasant

In general participants mentioned 3 sources (main occurrence and mean value), Greeks mentioned slightly more sources than French. There are no significant differences between circulated streets where many sounds are masked, and pedestrian streets where sounds can emerge more easily. No difference was observed either between countries, this means that the set of sound sources is typical of western urban environments and very robust across sites or countries.

Figure 1: Evaluation of the sound environment on the 5 point verbal scale. a) Kalamaria (Gr) and b) Paris (Fr). (% on the total number of answers per site) We observe a similar distribution of the answers on the verbal scale for the corresponding sites of the two countries: pedestrian sites are judged pleasant to medium, one-way narrow roads medium to unpleasant and finally, avenues are mostly judged unpleasant.

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As far as the identification of the sound sources is concerned we observe that people understand the concept of ‘sound source’ and mention entities from which sounds origin. They almost never identify the specific element or modality that actually produces a specific sound, like for example the engine or the brakes in a car. The main exception is observed for communicative sounds, like voices, klaxons or sirens often mentioned independently of their origin.

Finally, we distinguished a category called « Nature ». Natural sound sources are not a direct result of humans, although they are related to them by the urban ecosystem.

4.2 Presence and evaluation of sources Figure 2 presents the occurrences of the sound sources as these were mentioned by the participants, they are expressed in percentages on the total number of subjects per site. All mentioned sources were then evaluated on the 5 point verbal scale (cf. 2.2 ).

No particular sound identity was observed between countries apart from a slightly different perception of the sounds of children. In the Greek pedestrian site, they are occasionally accompanied by the ‘shouts’ of their mother, that is that culturally, they sometimes represent one sound source.

We observe that two of the super categories defined previously (Table 1) are highly represented in both countries: « Human » and « Activities ».

Finally, it was observed that verbalisations referring to the same sound event, used different expressions and revealed different levels of conceptualisation. For this reason similar meanings or terms were grouped in order to build a hierarchical classification and facilitate comparisons.

In the category « Human », it is the basic category « people » which dominates. Very often mentioned in pedestrian streets (76% people mention it in France against 67% in Greece), « people » is less mentioned when traffic increases but is always present. The basic category « shop keepers » is significantly present only in the French pedestrian street (19% of people mention it). This is certainly due to the specificity of Montorgueil street were many shops have open sections to the street. Sound presence of shop keepers is globally perceived as rather pleasant with the occasional exception of shop keepers ‘shouting’, judged as a noise pollution. In all the other sites, it is the word « shop » which is mentioned, referring thus to the activity, and rendering the actual sound sources vague and varied. Finally, the basic category « children » is almost always - even though sometimes moderately - represented in answers (16% of people mention it in the avenue in France and 7% of them in the other two streets, against 3% in the avenue in Greece and 42% in the pedestrian street). In France, it is the presence of school and college in our sites which necessarily implies the passage of children. This is not the case in Greece, where children's presence in the pedestrian streets seems to be a cultural specificity: typically mothers discuss on benches or terraces while their children play in the street.

4.1 Classification of sound sources A first classification of sound sources is proposed here (Table 1). It is based on the observation that the degree of human presence in sound seems to be of importance for people (explicative comments after questioning). Likewise, four super categories are distinguished, named « Human », « Activities », « Objects » and « Nature ». « Human » refers to all sources which directly reveal human presence. At a lower level, human sound sources are composed of « people » and two marked classes that generate specific sounds: « shopkeeper » and « children ». Participants commented these sounds as sounds reflecting life. In « Activities » are grouped all references which are related to a special human activity, sound being produced by the interaction of a human with a mechanical object. Six basic categories are discerned in this category (Table 1). Participants’ comments in this case usually refer to the object or to the user.

The super category « Activities » is mainly composed of the basic category « road traffic » (between 50% and 90% of the sources of this category). The « road traffic » category is judged very negatively in both countries and in all types of street.

« Objects » include sound phenomena which people did not relate to a human origin, either because human action in erased in perception or just because they concern purely sound objects.

Table 1: Hierarchical classification of sound sources Sound sources

Set Super categories Level 1

Nature

Basic categories Level 2

animals elements

Sub-categories Level 3

dog bird …

rain wind …

Human

Activities

people

shop keepers

children

street people static people pedestrians …

shop keeper shouts of fishmonger

shouts games school …

pedlar …

performances road traffic songs itinerant musician …

car motorbike bus lorry bicycle …

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Objects

shops

deliveries

works

restaurant café supermarket …

boarding lorry trolley …

building site road works compressor …

street cleaning

automous epiphenomenon sound objects

bin lorry cleaning service

siren bell cellular phone …

…

aircraft air condition …

background urban noise background noise …



percentage of subjects / site (%)

110 100 90 80

NATURE

HUMAN

ACTIVITIES

OBJECTS

70 60 50 ped-Gr ped-Fr ow -Gr ow -Fr ave-Gr ave-Fr

40 30 20 10

ba ck gr ou nd

ob je ct s ep ip he no m en on

or ks w

cl ea ni ng

so un d

categories of sound sources

st re et

er ie s de l iv

sh op s

tra ffi c

es

ro ad

pe rfo rm an c

ch il d re n

s ke ep er

pe op le

sh op

el em en ts

an im al s

0

Figure 2: Occurrences for each of the 14 basic source categories in the 6 sites expressed as percentage on subjects per site (ped: pedestrian, ow: one-way street, ave: avenue / Gr: Greece, Fr: France). The most negatively perceived sources in this category are motorbikes and lorries (judged unpleasant to very unpleasant). Busses and cars are a bit less unpleasant (judged unpleasant). Furthermore, « road traffic » is mentioned by approximately 100% of the subjects in avenues and one way streets, and by 67% and 80% in pedestrian streets for Greece and France respectively.

can be judged positively (birds) or negatively (animals, dogs, and also pigeons in France).

The omnipresence of vehicles in circulated streets explains these results, but the case of pedestrian streets is offered for discussion: even if a few cars or motorbikes occasionally pass from theses streets, how can one explain their perceptive omnipresence? One hypothesis is that the residual background noise is mainly composed of traffic sources. Another is that these sources are even more remarkable from the fact that they are prohibited in pedestrian streets. At the present progress of our analyses, this cannot be interpreted with certainty. We finally note here that the qualitative perception of traffic noise sources is not different between pedestrian and circulated streets.

Globally, in all streets, sources of human presence and natural sources are perceived positively whereas sources of activities and of specific objects are judged negatively (except « performances » and « shops »). It is encouraging besides to note that individuals are able to mention spontaneously sources which please them, knowing that it is generally easier to talk about what is unpleasant. Finally we observe that all evaluative judgements of the sources are directly related to the sources themselves and are not influenced by the context (type of street or country).

Finally, the super category « Objects » varies between 9% (French pedestrian street) and 28% (French avenue). The category most often mentioned concerns « sound objects », composed mainly of sirens (firemen, police, etc.) judged negatively (unpleasant in avenues).

4.3 Influence of sources on sound quality of the environment

Another category of « Activities » judged negatively was « works » (judged unpleasant to very unpleasant). It was only mentioned by 11% of subjects in average and as they concern transitory sound events, we can suppose that they have a small influence in the global evaluation of the sound environment. No significant difference was found between streets or countries. At the end, « street cleaning » is a basic category mainly mentioned in the French pedestrian street and also perceived negatively (judged unpleasant to very unpleasant). What is annoying here is not the noise itself but the moment of the day it is produced (1p.m. which corresponds to the lunch break in France).

Pedestrian sites are judged pleasant to medium, oneway narrow roads medium to unpleasant and finally, avenues are mostly judged unpleasant. Sound levels are similar between one-way streets and avenues, thus they cannot explain the differences found in the qualitative evaluation of the two types of streets. Furthermore, the number of sources mentioned and related to traffic is lower (or equivalent) in avenues than in one-way streets (153 and 103 in avenues and 171 and 109 in one-way streets for Greece and France respectively). Therefore it cannot be « traffic » noise that is responsible for the difference in the evaluation of the sound environment. The major differences in sources mentioned in these streets can be attributed to the category « human ».

The super category « Nature » is mentioned by a limited number of people. Occurrences vary from 4% to 18% (pedestrian streets in France and Greece respectively). Sources of natural origin like animals

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Indeed, the basic category « people » is mentioned twice more in one-way streets than in avenues. This result seems to confirm the hypothesis that it is the perceived degree of human presence which renders the sound environment more or less pleasant.

was observed to be between 0,2 and 1 in the studied sites; the higher this ratio is, the higher is the perceived sound quality. The interviews will be further analysed to complete the presented results, and also to search for groups of people and different strategies in answering.

In an attempt to establish a relationship between dominating sound sources a ratio between categories « people » and « road traffic » is proposed. This ratio, when of the order of 0,8, can still characterise a sound environment which is perceived positively (1 and 0,8 for the pedestrian roads of this study, Greek and French sites respectively). It is approximately 0,4 and 0,5 for the one-way streets which are considered medium to unpleasant, and drops under 0,3 for avenues judged unpleasant (0,17 and 0,28 respectively for Greece and France). This relationship should be explored further, tested in other sites and confronted to results obtained objectively. It will also be interesting to take other categories of sources into account.

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Finally, the relationship between the mentioned sources and their real occurrences in each site will be investigated; this relationship could also be associated to acoustic parameters (e.g. emerging level, etc.). Also, qualitative judgements will be correlated with physical parameters (acoustic, psycho-acoustic, etc.). This future work will be based on sound recordings and measurements already realised in the 6 sites. The final scope of this work is to enable the description of the quality of sound environments through the sources composing them, and to insert this description into more informative sound maps.

References

Conclusion and perspectives

[1] J.M. Fields et J.G. Walker, ‘Comparing the relationship between noise level and annoyance in different surveys: a railway noise vs. aircraft and road traffic comparison’. Journal of Sound and Vibration, 81(1), pp. 51-80. (1982)

The first results of this study allowed the evaluation of the quality of sound environments of 3 different types of streets in two countries, as well as the assessment of the present sound sources. Differences found in the qualitative evaluation of the sound environment of streets having a same LAeq, showed that sound level is not a sufficient indicator of the sound quality of an environment. This fact justifies the work towards the direction of sound sources.

[2] F. Guyot, ‘Étude de la perception sonore en termes de reconnaissance et d’appréciation qualitative : une approche par la catégorisation’. PhD thesis, Univ. du Maine, Le Mans. F. (1996) [3] R.F.S. Job, ‘Community response to noise: A review of factors influencing the relationship between noise exposure and reaction’, J. Acoust. Soc. Am., Vol. 83, No. 3. pp. 991-1001. (1988)

As far as sources are concerned, people seem to have similar sources in mind and the same number of sources (3 in average) concerning the composition of their urban soundscapes. Obviously, many sources effectively present on the sites are not mentioned, perhaps because there are not judged significant or are perceptively ‘transparent’. No major difference was found between the two countries, in occurrences, evaluation or meaning.

[4] J.M. Fields, ‘Effect of personal and situational variables on noise annoyance in residential areas’, Journal of Sound and Vibration, Vol. 93. No. 5. pp. 2753-2763. (1993) [5] ‘La gêne attribuée au bruit : approche anthropologique’, in Diagonal, No. 71, pp.38-41. Paris. (1988)

The source categories proposed here are close to those of Leobon [9] and Guastavino [6] which were established through other methods and validate further the present categories: « Nature », « Human », « Activities » and « Objects ».

[6] C. Guastavino, ‘Etude sémantique et acoustique de la perception des basses fréquences dans l’environnement sonore urbain’. PhD thesis, Univ. Paris VI. (2003)

Furthermore, the qualitative evaluation obtained for each source is globally stable whatever the street or the country considered. It seems thus uncorrelated from urban and cultural contexts. We should though take into consideration that the 5 options verbal scale used, is probably not accurate enough to reveal fine differences between groups of people.

[7] V. Maffiolo, ‘De la caractérisation sémantique et acoustique de la qualité sonore de l’environnement urbain’. PhD thesis, Univ. du Maine, Le Mans. (1999) [8] M.R. Schafer, ‘The turning of the world’. Knopf, New York. (1977) [9] A. Leobon, ‘La qualification des ambiances sonores urbaines, une manière d’apprehender l’usage de l’espace public’. Natures–Sciences–Société. (1997)

A ratio between dominating sound sources, « people » and « road traffic », can be proposed in order to estimate the quality of sound environments: this ratio

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