Urban park soundscape in distinct sociocultural and geographical contexts

The importance of soundscape in urban public parks has galvanised researchers concerned with improving the sound environment in cities. Existing literature reveals, however, a relative paucity of studies on soundscape in particular sociocultural and environmental contexts, and on the influence of these contexts in the perception of the urban sound space. Within this framework, this paper investigates the soundscape of parks in the cities of Belém, Brazil, and Lisbon, Portugal. The influence of geography and climate as determinant of activities and behaviors, the emission of natural and man-made sounds that characterise the soundscape of urban parks, the way park users evaluate the quality of sound environments were analysed, as were other elements that contribute for such an appreciation. The methodology encompassed soundmeasurements inside and outside the parks, analysis of the audibility of identifiable sound sources, study of local uses and activities through soundwalks and interviews, and assessment of responses to enquiries. The results shows that the soundscape of park depends on different features such as geography, climate, urban architecture, park infrastructure, sound sources, andmost importantly the visitors’ expectations for the planned activities, together with their other sensorial responses, which proved to be different in distinct sociocultural and environmental contexts.


Introduction
According to United Nations studies, two-thirds of the world population will be living in urbanised areas by the year 2050 [1].Human development conditions (such as life expectancy, health, education), however, indicate that such urbanisation will happen in an unbalanced way across different continents, countries and their administrative divisions, with advances and setbacks in human life expectancy and quality.Noise and its impact on human health and well-being [2][3][4][5][6] is one of the inevitable consequences of densification of human agglomeration and activities.Exposure of people to excessive noise levels is then a challenge, becoming a growing environmental concern.
In the midst of excessive urban noise, the sound diversity that identifies the city character and distinguishes one city from another is being diluted due to homogenization of technology and of social behaviors.To preserve the sounds that characterise urban environments invigorates the memory, the heritage, the cultural values; improves the quality of life of citizens; draws visitors; strengthens the economy; increases the value of real estate; and reduces costs with health when restorative spaces are made available.The soundscape of improved sound quality places and tranquil areas such as urban parks, gardens, and similar spaces, can benefit mental health and prevent the degradation of people's functional health [7].These areas facilitate walks, childplay, and other leisure activities that increase social interaction, emotions, and motivate life.
In general, classical policies of noise reduction and control in urban environments have failed to achieve the desired goals of limiting noise or avoiding degradation of the sound quality of public spaces, either by financial, technical, or functional constraints, and have also neglected the subjective side of human perception.Urban public parks are privileged areas in a city due to their environmental quality, particularly their sound, and the peacefulness they offer to the people who seek it.An effort of the scientific community to study the soundscape of urban public parks, due to their importance for leisure and recovery of individuals has been observed recently [8][9][10][11][12].
Soundscape is understood as the acoustic environment of a place, perceived or experienced by people in its context, which results from the action and interaction of natural and/or human factors [13][14][15].The sound contents and the geographical environment are important, but so are the objective functions of the place, the human activities, and the user's expectations that contribute to the listener's appreciation, which becomes important in soundscape management [16,17].
Among the gaps in theoretical and empirical investigation found in the literature are studies of soundscape in distinct cultural contexts, and the relationship between objective and subjective components in the analysis of urban sound environment [13,14,18,19] are part of the methodological limitations.

Objectives
Within this framework, a study was set up to investigate the soundscape in urban public parks in Lisbon, Portugal, and in cities of Southamerica, namely Brazil, in an attempt to understand and characterize the park soundscape in their quite distinctive sociocultural and environmental contexts.Would the different contexts seriously impact on the local soundscape?
The results presented herein refer to the cities of Lisbon and of Belém, and are part of the ongoing research.

Methods and Results
Belém is a densely urbanised city with one and a half million inhabitants, located in the Amazonian region in northern Brazil, near the Equatorial line.Climate is hot and humid all year round, with an average monthly rainfall of 60 mm.Lisbon, on the other hand, has a population of about one million people and is located in the westernmost portion of the European continent.It enjoys around 260 sunny days in a year, and its climate is temperate oceanic.Figure 1 shows the geographical location of the two cities.
In Belém, the Rodrigues Alves Botanical Garden (BRA), the Zoobotanical Garden of the Emílio Goeldi Museum (PZB), and the Batista Campos Square (PBC) were studied.In Lisbon, the Estrela Garden (JES), the Calouste Gulbenkian Foundation Garden (JFG), and the Príncipe Real Garden (JPR) were considered.These sites were cho- sen following preliminary studies [20] for their importance in the city, in the sense that they integrate urban cultural programs and are well visited.They have different features, uses, and locations within the urban area, as Figures 2 and 3 show.Their sizes span from a typical city garden (such as the Principe Real Garden with 1,15 ha) to an urban tissue park (such as the Rodrigues Alves Botanical Garden with 14 ha) thus covering most such areas used by citizens as city gardens or parks.Various procedures were followed for capture and analysis of local data, both in situ and at the laboratory.Sound measurements and recordings were carried out; soundwalks were performed [13,21]; recorded sound signals were analysed and processed at the laboratory to determine thresholds of audibility [22,23] of the different audible sounds; and opinion surveys were used by means of questionnaires directed to users [21,24,25].
Field work identified sound sources and elements of identity, infrastructure and safety; signs of transgression and negligence; construction works; operating machinery and equipment; as well as flora and fauna present in the parks.Soundwalks, allowed identifying and locating in each park the different sound contributions: road traffic, other electromechanical sounds (ventilation, construction, and recreation), human sounds (voices, childplay, yelling), animal sounds (mostly birds), and other natural sounds (water, wind through leaves, rain).
Points were selected next to sound sources audibly identified as relevant where sound pressure levels, L Aeq , were measured in 1/3-octave bands.Although in general ISO 1996 [26] measurement procedures were followed, only short time values (signal samples of about 7') were considered since long term averages are not applicable here, except for the road traffic sound component.The aim was to quantify at reference positions typical sound pressure levels of people talking, of children playing, of birds  and other animals singing, of water fountains, as well as of road traffic or of other mechanical sources.Tables 1 and 2 indicate the location of the sound sources and the recorded L Aeq values.
For each park, an acoustic model was built based on the L Aeq measured values and on other data such as vehicle counts and characteristics of surrounding roads, building heights, and location of sound sources, so as to allow for the calculation of the spatial distribution of sound levels using the NMPB method [27] for road traffic and the ISO 9613-2 method [28] for point sources, to draw sound maps.
The sound maps for the different parks are shown in Figure 4.The maps represent sound pressure levels (L Aeq ) in 5 dB intervals, from below 45 dB up to above 75 dB, with different colors.The color code is also shown in the figure.These are not average values.The maps represent typical sound level distributions when all sound sources of relevance (audibly identified) are present.Of course, these maps vary during the day and along the year.But so do visits to the park.In a typical day (when more visitors are present), these are the expected sound maps.
Sound recordings with samples of at least 30 sec were made using a digital 24-bit, 96 KHz, double-channel recorder to determine audibility thresholds of the different sound sources in the parks, based on human perception, language and sound levels.In Portuguese parks, recordings were made along their respective visiting circuits; in the Brazilian parks, with their undefined visiting circuits, recordings were performed near the most expressive sound sources.
The sound recordings were analysed in the laboratory (anechoic chamber) as per the experimental setup shown in Figure 5.Following calibration of the system, white noise was introduced progressively and simultaneously with the sound under study until the latter was completely masked off, thus reaching the audibility threshold;  at this point, the masking level L mask corresponding to the perceived reference sound level of the sound source, was recorded.The values found by following the procedure for different points allowed the building of the corresponding point sound source radiation model and the drawing of the sound audibility curves.This procedure was followed for all sound sources of interest in each park.Figures 6 and 7 show the audibility maps of the main sound sources in the parks.The color code is that shown in Figure 4. Again, these maps do not represent long term average values but typical sound distributions of the specific sound sources when they are present (water fountains are not always turned on, children are not at the playground all the time, and birds are not always on singing mood; but when they are, these are the expected sound distributions).
A questionnaire was applied to park users, randomly chosen (at least twenty per park, in a total of 180) with their profile established (gender, age group, employment status, schooling level).Questions included: place of dwelling; frequency of visits; period of stay and reason for visiting the park; how the person evaluates infrastructure, facilities, beauty, pleasant and unpleasant features of the environment; personal perception of quality and of level of sounds inside and outside the park and at the moment of entering or exiting; and the feeling of peacefulness.The responses' grade varied in accordance with the type of question from yes/no, a description, or a five option answer (such as very satisfied, satisfied, neutral, unsatisfied, and very unsatisfied).
The opinion surveys revealed that Portuguese parks are more often visited than the Brazilian ones, but the period of stay is longer in the latter (85 to 100% -one hour or more) than in the former (40 to 45% -less than one hour).The main reasons for visiting parks were leisure and contemplation (Brazilian 80%, Portuguese 72%).As for the respective infrastructure and facilities, more Portuguese interviewees (88%) revealed to be more pleased than the Brazilian ones (48%).Among those not pleased, the Brazilians (40%) vastly outnumbered the Portuguese (5%).With reference to the beauty perceived in their respective parks, 86 to 90% of the Brazilians and the Portuguese declared to be very pleased and 40 to 65% of them just pleased.Some people expressed dissatisfaction with the beauty of BRA (15%) and PBC (10%) in Brazil.
Among the features of their respective parks found to be pleasant, Portuguese interviewees mentioned the environment as a whole (30%), ducks (23%) and small birds (12.5%).Their Brazilian counterparts referred the vegetation (43%), the animals (12%), the shades and animal sounds (5%), as Figure 8 reveals.
While 25 to 60% of the Portuguese answered there were no unpleasant aspects in their parks except for stray dogs and their dung (5 to 15%) as well as overflying aircraft in JFG (30%), 23% of the Brazilians considered unpleasant the dirt and rubbish, particularly in PBC.As for the perception of the sound environment as pleasant or unpleasant, Children at playground 58.9  natural sounds were better appreciated in Brazilian parks (95 to 100%) than in Portuguese ones (61 to 63%).Road traffic sounds, perceived in most parks, were not mentioned by visitors of BRA (80%) and PZB (60%), and more Brazilians (65 to 80%) than Portuguese (42 to 66%) considered them unpleasant.Although regarded as unpleasant in both countries by 10 to 11% of park visitors, machinery and equipment sounds were perceived more by Brazilians (17%) than by Portuguese (12%).Conversely, other sound types were better perceived by the Portuguese (19%) than by the Brazilians (3%); human sounds were noticed by 10% of interviewees in both countries and deemed as unpleasant (3 to 10%).
Eighty-five to ninety percent of Brazilian interviewees and 50 to 75% of their Portuguese counterparts stated they did not mind the level of the overall sound in their respective parks, which was considered normal by 55 to 88% of visitors in both countries.
More Brazilians (73%) than Portuguese (52%) expressed their satisfaction with the peacefulness of the respective environments.However, as indicated in Figure 9, more Portuguese (27%) than Brazilians (18%) said they were very happy with that peacefulness.
Perception of sound quality changes drastically when the user enters or exits the park, as pointed out in the synthesis of answer excerpts on Table 3.Although some com-

Inside
Outside "Inside the park, it is better, more natural, pleasant, peaceful, silent, I hear better the sounds of birds and of the wind.In the middle of the park the sounds become more muffled.When the wind blows, the trees don't allow polluting sounds inside.My mind can easily detach, I keep everything else outside.I can focus on doing things".
"Outside it is much worse, it is the urban reality.Sound volume is constant, traflc is more intense, we can hear everything that happens, there is sound pollution, noise, cars and bikes, smoke, total chaos.Inside the park we can't hear the racket here outside".

PZB Inside
Outside "Inside nature rules, the atmosphere is more relaxing, more soothing, the air and the sounds are different from out there.It makes us feel like we are in the countryside.It is much more peaceful, quieter, sounds are more pleasant and the volume lower.We can listen to the wind rustling through the trees and the birds".
"Outside the sounds and noise are stronger, louder, the cars are noisier and more unpleasant.We can't hear well at all.Klaxon sounds are deafening, disturbing".

PBC Inside
Outside "Inside it is more peaceful, silent and the sounds are more pleasant.Comparing to the traflc sounds outside, noise level here is quite low.In the middle of the park it is even more peaceful and we can barely hear the sounds of cars.There is a feeling of serenity, we can listen better to the birds, there is more tranquility".
"Out there traflc noise is suffocating and more unpleasant than the natural sounds in the Square.There is sound pollution, car and motorcycle noises, sounds are more aggressive".

Lisbon JES Inside
Outside "Inside it is more pleasant, peaceful and less bothersome.Natural sounds predominate, although some traflc sounds can still be heard.We don't have to raise our voice to be heard".
"Outside there is more noise, rattle, and depending on the hour it can become more agitated".

JFG Inside
Outside "Inside we can hear less the sounds of cars and machinery and those of nature and birds prevail.The environment is more natural than on the street.Sounds can be loud or low, but are more diversified, pleasant and relaxing.There is calm and tranquility.When I leave this dome, outside it is just chaotic traflc.It can be annoying due to daily city noises, but I regard that as normal".
"Outside the sounds are loud and negative.There is sound pollution, traflc, chattering and much more noise.We have to raise our voice to be heard.Urban sound muffle those that are natural".

JPR Inside
Outside "Inside the environment is better, more silent, and we hear less car noise.There is a variety of sounds, typical of gardens (birds, fountains), some of them quite pleasant".
"Outside there is an intense road traflc, more noise caused by buses, lorries and motorcycles".ments may seem repetitive, it is interesting to note that they refer to very different parks, in size, character and context.

Discussion and Conclusions
Geography and climate determine behaviors, which generate human and natural sounds that contribute to define the soundscape of urban public parks.
In wintertime in both Belém and Lisbon the urban environment is less lively.Comparing the environment of the parks under study in the winter, open air activities are reduced, if not entirely paralysed, either due to the cold weather (Lisbon) or to the rain (Belém).Among park users, sportspeople are the most resistant to harsh weather, either walking or running in or around public parks.
In Belém, the sound produced by the attrition of vehicle tires against the pavement was observed, made more relevant by the vehicles' speed and the rainfall.It must be noted that the sounds of rainfall are part of the collective memory of Amazonian people.
In wintertime, the aesthetic/visual landscape is altered by the loss of tree foliage in cities like Lisbon, which reflects upon the behavior of animals and also on that of the wind, whose sounds are important contributions to the soundscape, with a positive evaluation by the listeners.The year's seasons, according to the geographic location of each city, define the seasonality of food and the behavior of urban birds on the park trees, which affects the time period in which they produce "pleasant" sounds (in the sense that they are appreciated by the listeners and thus they are sounds of preference) in the respective environment.Frequency of bird sounds in the winter is much lower than in the summer or early spring.In fact, spring is associated with the return of foliage in trees, as well as of flowers and fruits, which attract pollinating insects upon which birds prey.
Beyond the shapes, colors and smells, all relevant when evaluating the quality of the environment, vegetation, which counts among the pleasant features in parks for 43% of the Brazilian interviewees, represents food and shelter for singing birds.The parks surveyed shelter nests or temporary bird species such as cranes, ducks, peacocks, parakeets, doves, and others, whose sounds are liked by

Activities
Belém Lisbon Get together with teenage classmates in gazebos or around benches for talking, amusement, singing, and playing music; BRA-PZB-PBC JES-JFG-JPR the park visitors.PZB and BRA in Belém, both charging entrance fees, harbor species of tropical animals whose sounds are much liked, as they have become rare in the urban milieu.
In the three Belém parks, plain parakeets (Brotogeris tirica) eat mango (Mangifera indica) and the fruit of the kapok tree (Ceiba pentandra).Their song fascinates those unfamiliar with the species, but it can also be a source of annoyance for local dwellers who see them on a daily basis.The audibility threshold for the vocalisation of a peacock (Pavo cristatus) on the roof of the administration building in JES, of a flock of great egrets (Ardea alba) on the kapok trees of PBC, of a flight of parrots and a couple of giant river otters (Pteronura brasiliensis) in PZB pens reached distances of 300 m, 250 m, 160 m, and 120 m, respectively.
These results and observations illustrate how songbird behavior is important for the study of how natural sounds contribute to the urban soundscape.Depending on the park user's expectations and on the types of activities, the natural sounds of some birds, usually perceived as pleasant, can instead be regarded as unpleasant.The same can be applied to some mechanical sounds, which are not necessary always perceived as noise.Some traffic sounds can blend nicely with others to convey a notion of liveliness, unless you require calm and tranquility.
In Summer, everything becomes more lively.With less rainfall in the tropics and the absence of cold temperatures in temperate regions, people get out more often and fill the streets and public parks, bringing along their own habits and typical sounds.
Meteorological conditions, especially air humidity can seriously influence sound propagation.In places with high temperature and humidity, such as Belém, the speed of sound can increase by 0.33 m/s per degree of increasing temperature.These effects particularly influence the frequency contents of the sound.It can then be expected that the sound composition varies from point to point in a more pronounced fashion in a city like Lisbon than in Belém, where the average humidity values and temperatures are much higher.
In all parks, sounds of moving water, such as streams, fountains, or artificial waterfalls, were perceived and evaluated by the users as pleasant.This type of sounds were seen to contribute to the effect of masking other sounds from outside (especially traffic noise) thus influencing the subjective evaluation by the listener [29].Other components of the place such as still water ponds or lakes, which produce no sound but reflect the sky, or vegetation, espe-cially when it is dense, and even people contribute to a positive appraisal of the environment inside the park.The users' responses showed a clear effect of mental masking in line with findings reported in the literature [30,31].The presence of elements of preference, not necessarily just sonic but also visual, as mentioned, help to divert the attention of the listener, changing the perception and thus the local soundscape.
An aspect that differentiates one society from another and clearly reflects on the sound environment of their respective parks is the degree of the technological development of mobility, which can be ascertained, e.g., by the vehicle fleet moving around the parks.Lisbon offers more public transportation alternatives (trams, underground railway, and buses) than Belém, while in the latter a mixed bag of buses and vans link the core of the city to the outskirts, but concentrate in and jam the main traffic axes.Therefore, the contribution of road traffic noise, as clearly shown in Figure 4, is relevant to the sound perceived inside the parks, as stated by the interviewees (see user comments in Table 3).
Park visitors in both Belém and Lisbon perceived and evaluated the road traffic sounds, particularly those caused by motorcycles, as "noisy and disturbing".The recent improvement of the economy in Brazil resulted in a growth of consumption by the population, namely of light automobiles and motorcycles.On the other hand, the low investment on public transportation in Brazil has led to an increase on the use of personal transport that jams and endangers the traffic and pollutes the urban environment.
Observations in the two cities showed clear differences in land use and urban development around the parks that may affect conditions of perception inside the parks and thus the soundscape.Urbanization in the vicinity of Belém's parks is less dense than in Lisbon, where it is fully consolidated.Here, one can observe a higher respect for traffic regulations and other social norms with some social insecurity being reported in Belém.These social conditions reflect upon the capacity of the park user to relax and fully appreciate the inner atmosphere of the public park and consequently impact on the local soundscape.
Despite the fact that both the quantitative and qualitative analysis indicate that the technological characteristics of vehicles tend to homogenize the urban sound environment, the soundscape of a public park results from different features such as geography, climate, urban architecture, park infrastructure, sound sources, and most importantly the visitors' expectations for the planned activities, together with their other sensorial responses, which are different in distinct sociocultural and environmental contexts.
Visitor activities observed in the parks of Belém and Lisbon are quite diverse, as summed up in Table 4.Besides the normal activities, as recorded in the table, some events such as music, dance, or poetry presentations, and stage performances were identified as relevant in the present study.Events attract more people, generating more sounds, especially human sounds, considered pleasant by 90% of the interviewees.
Safe, clean, and well maintained environments that include natural elements such as vegetation, water sources, wind, animal and human sounds, in an overall coherence and in context with the users' activities are evaluated as pleasant both in South-American and European places.Parks with these attributes, in appropriate weather, motivate their users to remain inside for longer restorative periods of time before returning to the "urban reality", to face features such as road traffic, regarded as unpleasant in both contexts.
The will to and the act of entering a park lead to a "mental disengagement" from the outer urban context, where sound levels deemed high (typically above 65 dB(A)) do not affect the perception of the environment as being of good quality, nor determine the visitors' sensation of wellbeing and peacefulness.

Figure 1 :
Figure 1: Relative location of the cities of Belém, Brazil (a), and Lisbon, Portugal (b).

Figure 4 :
Figure 4: Sound maps of parks in Belém and in Lisbon.

Figure 6 :
Figure 6: Audibility maps of main sound sources in Belém parks.

Figure 7 :
Figure 7: Audibility maps of main sound sources in Lisbon parks.

Figure 8 :
Figure 8: Evaluation of sound environment by park visitors.

Figure 9 :
Figure 9: Evaluation of peacefulness in Brazilian (left column) and Portuguese (right column) parks by their visitors.
BRA-PZB-PBC JES-JFG-JPR Perform individual and collective music shows, dance or plays, with amplified sounds, for the general public in a given place; BRA-PZB-PBC JES-JFG-JPR Walk with groups of friends or acquaintances for talking and amusement; BRA-PZB-PBC JES Exercise in group with friends or acquaintances, talking and amusement, in a given place; BRA-PZB-PBC JES Play with other children, move along and amuse themselves in playgrounds; BRA-PBC JES-JPR Play with other children, amuse themselves and move along tracks and trails; BRA-PBC Play with barking dogs in different places; PBC JES-JPR Get together with elderly friends to play, chat and amuse themselves on chairs and at tables in a given place; BRA JES-JPR Play with noisy toys sold at the park entrance; BRA Reproduce amplified sounds on bicycles; PBC Rent electric minicars for children and roam around along tracks and trails; PBC Get together with other students from schools around the park for conversation, music playing, singing and amusement; PBC Get together with other students from schools around the park for running contests along tracks and trails; JES Get together with friends at restaurant and café terraces; BRA-PZB-PBC JES-JFG-JPR Sit in a quiet corner to read.

Table 1 :
Point / Sound sources in Belém parks.

Table 2 :
Point / Sound sources in Lisbon parks.

Table 3 :
Summary of responses on the perception of sound in parks in Belém and Lisbon.

Table 4 :
Leisure activities in parks in Belém and Lisbon.