Framework for urban sound assessment at the city scale based on citizen action, with the smartphone application NoiseCapture as a lever for participation

2.3.1 Recruitment of participants

A series of events were organized, supported by the city’s communication services, in the form of a special section on the city’s website and press release, in order to communicate about the project and the search for participants (see their date in the agenda of the experiment in Figure 3):

• A public kick-off meeting brought together more than 30 residents to launch the project on 01 December 2021:

• The project then received media coverage from the regional and national French press during the month of December. This dissemination allowed publicizing the approach while communicating with the general public on urban noise environments issues.

• A special event was organized as part of the “Unesco Week of Sound,” which is an international event that promotes noise awareness, on 15 January 2022.

• One article was published in the city local journal in February 2022.

• Four events were organized on the city’s markets in March 2022, during which the project members had a stand and went to meet the residents.

Figure 3

Dynamics of data collection. Top: Number of new measurement tracks as a function of time. Bottom: Number of new participants as a function of time.

The participation process was completely open. Residents informed of the experiment through the various communication channels were invited to download the application and take measurements and eventually to approach the researchers to join the group of participants by leaving their e-mail address or joint the social network group. The focus group interviews were also the subject of a communication, internally via the group of participants constituted, and through the city’s communication services.

2.3.2 Data collection

Data collection lasted 7 months, extending from December 2021 to June 2022 inclusive. The participants were free to take measurements whenever they wished, with the instruction either to take measurements in spots of at least 1 min or to take mobile measurements, taking care not to pollute the measurements with their own steps and to pay attention to the weather conditions (avoid either rain or gusts of wind). In addition, a page dedicated to perception, present in the NoiseCapture application, allowed participants to fill in perceptual variables: tag the sound sources heard (on/off), and give a sound environment pleasantness rating.

A smartphone calibration was carried out at each organized event for participants who wished to do so, in order to improve the quality of the collected data. A mailing list and a social network discussion group were created, in order to maintain the momentum around the project. However, since for reasons of anonymity, it is not possible to know the telephone number of the people who have downloaded the application, it was not possible during the project to send messages to people who are taking measurements and have not left their e-mail addresses. As a result, some of the data collected came from not calibrated smartphones, which the application keeps track of.

Finally, five NoiseCapture parties were organized from the 5th month onwards, with the idea of carrying out measurements in areas poorly covered by the experiment, with internal communication. These NoiseCapture parties took place on 27 April 2023, 07 May 2023, 16 May 2023, 31 May 2023, and 14 June 2023. The idea was to bring together residents to carry out measurements over a period of about 30 min and then followed by an informal discussion on the sound environments heard.

Measurement tracks, which consist of the sound levels and GPS position at a 1 s resolution, the presence of sound sources for the whole measurement track, and meta data (calibration value of the smartphone and Id number of the participant), were sent continuously by the participants through the experiment (an option in the smartphone application allows a participant to either send the data at the end of each measurement track or by batch at a chosen time). Finally, data were post-processed for the production of noise maps. Therefore, the objective is not to relate the collected data to long-term health impacts but rather to follow a short-time capture approach, more related to short-term disturbance. The influence of measurement duration and timing on the maps produced is discussed in Section 4.1.

2.3.3 Data treatment

2.3.4 Focus group interviews

In addition to the kick-off meeting, which brought together more than 30 residents, the event of the 15 January 2022 and the five NoiseCapture parties, each of which gave rise to informal exchanges about sound environments, two focus group interviews were organized. These focus group interviews involved elected officials, residents, and researchers, with the idea that the residents freely express themselves on the city’s sound environments, in their positive or negative components. Focus group interviews are a recurring feature of soundscape research. They are for example used by Bruce and Davies [37] to show the impact of expectations relative to a soundscape on its appreciation, by Jia et al. [38,39] to question the dimensions of soundscape worthy of preservation, or by Davies et al. [40] to show the descriptive elements used by individuals to describe soundscapes. In the study by Manola et al. [16], focus group interviews were conducted to observe the dynamics of the development of a soundscape diagnostic method within different professional (acousticians, space designers, and artists), institutional and resident groups.

The focus group interviews, which lasted about 90 min, were prepared in advance together by the elected officials and the researchers:

• The first focus group brought together nine participants on 4 April: six residents, one local elected official, and two researchers. The residents were invited to bring an object related to their relationship to the city’s sound environment, to initiate a round table discussion. The open discussions were then oriented on the perception of the sound environments of the city, along with questions on the sensitivity to noise and the variety of the listening situations. Questions were then asked about how the experimentation was modifying the participants’ relationship with the city’s sound environment. First elements concerning possible noise mitigation solutions were finally discussed.

• The second focus group brought together seven participants on 18 May: four residents (one of whom had taken part in the first discussion group), two elected officials, and one researcher. After a quick round table discussion, the discussion focused on the links between sound environments and ways of living in the city. A collective discussion then focused on the actions that could be implemented to improve the city’s sound environments, introduced by an overview of possible actions against noise presented by the researcher.

These discussions were audio-recorded, with the verbal informed consent of all participants, to be transcribed for detailed analysis while preserving the anonymity of the participants.

2.3.5 Semi-directive interviews

Ten individual semi-directive interviews with participants were also conducted by a Master 2 student [41] at the end of the project, in order to determine the residents’ reasons for participating in the process and to understand whether their perceptions of the sound environment had changed and their involvement in the project and their willingness to participate in a citizen’s group committed to the issues of the noise environment at the city scale.

2.3.6 Closing seminar

Finally, the project gave rise to a closing seminar on 25 June 2022 for the residents of Rezé. The event included a scientific report, consisting of a presentation of the maps produced and a summary of the focus group interviews. The residents were also invited to give feedback on the experimentation. The seminar also included original artistic performances, as local artists (a saxophonist, a drummer, and a couple of circus performers for three performances of 8 min each) were invited to present improvisations based on an audio sound scene representative of the Rezéan sound environments, composed from field recordings. The project was also accompanied by an illustrator, who helped to make the approach tangible for the residents. Finally, a round table involving residents, the city of Rezé (elected officials and technical services), and researchers was organized. The participation of residents in the diagnosis and improvement of sound environments was discussed, as well as a possible follow-up to the project, with all parties agreeing on the relevance of continuing the experiment.

3.1.1 Dynamics of measurements

After 7 months of data collection of the experiment, the number of participants was 134. The total number of measurement tracks made was 1,566, for a total duration of 93 h, which is a mean measurement duration of each measurement track of more than 3 min. The median duration of measurement tracks is 66 s; 90% of the measurement track last 6 s or more, and 10% of the measurement tracks last 5 min 40 s or more. The detailed temporal evolution of the number of participants and the number of data collected is depicted in Figure 3. More details on the dynamics of measurements can be found in Can et al. [42]. The main results are as follows:

• The importance of the events organized to maintain activity around the community, with a strong increase in the participation observed after each event.

• The constant slowdown in participations, with for instance few measurement tracks collected in March. This shows the difficulty in getting people involved in the measurement in the long term. This is however countered by events such as the NoiseCapture parties organized during the last two months. Indeed, the 5 NoiseCapture parties amounted to 3.9, 1.8, 1.8, 2.8, and 1.9% of the total duration of collected data, respectively, that is a total of 12.3% of the collected data in a short duration.

• The impact of external factors such as school holidays or weather conditions on participation, with almost no data collected during the Christmas school holidays, whereas the good dynamics of the two first weeks of December. In addition, the number of measurements per participant is heterogeneous. Among the 134 participants, 48 participants took five or more measurement tracks, 30 participants took 10 or more measurement tracks, 18 participants took 20 or more measurement tracks, and 4 participants took between 100 and 230 measurement tracks. The same heterogeneity stands for measurement durations. Among the 134 participants, 72 participants took 5 min or more of measurements, 45 participants took 15 min or more of measurements, 22 participants took 1 h or more of measurements, and nine participants took between 3 and 10.5 h of measurements.

The temporal distribution of the collected data is depicted in Figure 4. The distribution of measurements within the week is heterogeneous, with almost three times more measurement tracks collected on Tuesday than on Sunday. The distribution of measurements is also heterogeneous during the day, with a strong peak in the number of collected measurement tracks between 16:00 and 17:00. All time periods between 4:00 and 23:00 are represented, although the times of the day before 7:00 and after 21:00 are poorly covered. The absence of data collected at night explains the choice of selecting the L _{A50,[8−18h]} as an indicator, since data would have lacked for estimating L _night and consequently L _den values. However, given the data treatment described in Section 2.3.3, which relies on the difference between the median of L _Aeq,1s values at a given time slot and the median of all data collected between 8 h and 18 during a weekday, the temporal heterogeneity during the day and during the week has no influence on the calculated L _{A50,[8−18h]} value.

Figure 4

Temporal distribution of measurement tracks. Left: number of tracks for each day of the week. Right: number of tracks for each hour of the day.

The spatial distribution of the collected data is depicted in Figure 5. It highlights the spatial heterogeneity in data collection, with a much higher density of measurements in the north of the city than in the south. This is explained by the fact that the population densities are higher in the north, which contains many buildings than in the south, which contains mainly individual houses. The five organized NoiseCapture parties (see Section 2.3.2 and black circles in Figure 5) helped to counter this heterogeneity and to gather data in areas poorly covered.

Figure 5

Density map of the L _Aeq,1s data collected. The black circles represent the five NoiseCapture parties.

3.1.2 Produced sound environment maps

Sound environment maps were produced following the method described in Section 2.3.3. The maps depicted in Figures 6 and 7 are those that were presented and discussed with the residents during the final seminar on 25/06/2022. Possible improvements to the method are discussed in Section 4.2. The L _{A50,[8−18h]} map depicted in Figure 6 can be compared to the multi-sources (road traffic + rail traffic + aircraft traffic + main industries) L _den strategic noise map. The produced L _{A50,[8−18h]} map is in accordance with expectations. It highlights the contrast in sound levels between major and minor roads, although the lack of data around the ring road in the South prevents highlighting the high sound levels here. Interestingly, the produced L _A50[8−18h] map is sensitive to sound level variations in no traffic zones as parks (see North East along the river for instance), whereas the strategic noise map depicts no data here. Some inconsistencies, however, such as high-level spots in quiet neighbourhoods, were noted by residents. They are the result of an insufficiently long data collection, which is thus sensitive to outliers in measurements. In addition, participatory measurements cannot cover all the weather conditions that occur during a year, which are averaged under the strategic noise maps modelling.

Figure 6

Produced sound levels noise map. Left: map of L _{A50,[8−18h]} produced during the project. Right: multi-sources (road traffic + rail traffic + aircraft traffic + main industries) L _den strategic noise map.

Figure 7

Sound-oriented noise maps. Top left: map of perceived presence of rail traffic sounds. Top right: strategic noise map for rail noise. Middle left: map of perceived presence of aircraft traffic sounds. Middle right: strategic noise map for aircraft noise. Bottom left: map of perceived presence of road traffic sounds. Bottom right: map of perceived presence of animals.

Finally, Figure 7 represents the map of the perceived presence of rail traffic sounds, aircraft traffic sounds, road traffic sounds, and animal sounds. These sound sources are selected because they are related to perceived sound pleasantness [4]. The other tags contained in NoiseCapture offer the possibility to map amongst others the perceived presence of voices, children, music, vegetation, water sounds, works, or industrial sounds. The sound source-oriented noise maps are in line with expectations and were considered by the residents during the closing seminar as an interesting alternative to the classical noise maps. The details are as follows:

• The map of the perceived presence of rail traffic sounds follows the tramway line, which crosses the city. It is in accordance with the strategic L _den map for rail noise. The rail traffic tag was activated for 3.5% of the tracks that contained an activated tag;

• The map of the perceived presence of aircraft traffic sounds shows a higher density in the heard air traffic sound sources in the south west of the city, as one gets closer to the airport, which is located 4.5 km southwest of the city limits. It is in accordance with the strategic L _den map for aircraft noise. The air traffic tag was activated for 28.3% of the tracks that contained an activated tag;

• The map of perceived presence of road traffic sounds shows a high density in the heard road traffic sound sources everywhere in the territory. This map however fails to discriminate between major and minor roads, as the sound sources tag under NoiseCapture is “on/off.” The road traffic tag was activated for 80.4% of the tracks that contained an activated tag;

• The map of the perceived presence of animal sounds is consistent with the parks and green areas of the city, hence potentially highlighting areas suitable for restorativeness. The animal tag was activated for 30.8% of the tracks that contained an activated tag.

3.2.1 Towards a discursive diagnostic of sound environments

The focus group interviews drew up a discursive diagnosis of the sound environment of the city of Rezé, highlighting the diversity of the sound sources heard in the area, but also the diversity of perceptions and the importance of the different temporalities making up the city’s sound environments.

3.2.2 Diversity in sound sources, perceived both negatively and positively

Two sound sources were at the core of the discussion and on which there was consensus, namely road traffic and air traffic, illustrating the concerns of residents of a city crossed by significant commuting traffic and under an air corridor of an airport located less than 5 km away. Air traffic, in the first place, focuses the attention and is a source of exasperation manifested by the residents: “I remember one morning at the end of the summer… I sleep with the window closed, it’s not possible otherwise… and even so, with the window closed, I had about ten planes taking off between 6 and 7 in the morning, it was hellish.” (P2). Road traffic, perceived more as a continuous stream present without respite at all hours of the day, is also a source of exasperation: “I really have the impression that now; maybe even more in the South of the ring road, there is traffic all the time! All the time! At any time of the day. and then in the morning, it’s incredible […] And it’s trucks, trucks, trucks.” (P2).

Other sound sources perceived negatively, which may seem more anecdotic but which constitute urban sound mixtures, were also mentioned, such as glass containers, stadium, or manhole covers. It seems that, for these sound sources, further focus group interviews involving new participants would multiply the diversity of testimonies: “I witnessed it one day, in the Place du 8 Mai, people were putting in the receptacle for the glass, a horror. I didn’t have the application to measure the noise, but it was really a horror.” (P11). “There is another noise that is quite infernal, and I didn’t think it would be so much, it’s the stadium” (P2). “The manhole cover… the trucks when they pass over it, and then as it is always in bad balance it… “clong clong” (P3).

The focus group interviews also drew a portrait of a city with quality sound environments, driven by green spaces and preserved residential areas. Hence, sources such as parks (cited as a location rather than as a sound source), music, or birds were cited: “Then there are three parks there, I don’t know if you know the area… which are rather pleasant, and if I have to take one of the parks, there is a square behind the buildings, so it’s quite protected from all the road noise, passage… and when you’re there, you don’t feel like you’re in the city.” (P7); “There are some very pleasant noises, not only the noise of planes. I live not far from the Balinière, between the planes I hear very pleasant things, as it’s the music school, we walk in the streets, we enjoy the children and adults who play at the Balinière school, and it’s true that in the summer in particular, it’s great because they have the doors and windows open there, and so do we, and everyone in the district enjoys it. It’s very pleasant, the piano, the violin…” (P12); “It’s a cherry blossom tree, where there are a number of birds, and they make the most noise.”(P9).

3.2.3 A diversity in perceptions among the residents

A strong link between the perceptions expressed by the residents, their living environment, and their experience of sound appeared in their comments. The perceived sound environments thus take on an individual dimension, which leads to a lack of consensus on certain sound sources, such as stadiums or cafés: “No, there is a need for cafés. The new café on Charles Rivière Street, I find it closes early.” (P9). “And I find that the streets are very pleasant, when I’m on my terrace I can hear the children in the playground on rue Salengro. It’s something that reassures me, it’s lively at the same time […] I actually love this neighborhood.” (P12).

Finally, the discourse on sound environments was accompanied by a psychological dimension, which is known from the literature and is widely acknowledged and expressed by the residents. This is particularly true when the discussion focused on mobility or aircraft noise: “Noise is very strongly linked to the psychology of noise association. Personally, there is a big problem with airplanes, it’s not just the noise, it’s a next step, I think ok the problem with airplanes is the conflict between modern society which says we must protect the planet, take the plane less often, the CO ₂ and then we see the traffic increase. And when I think afterwards, all the citizens of Nantes who say ok we have to reduce CO ₂ , and then they take the plane for the weekend to go to Portugal for a drink with friends. It’s not consistent for me, and maybe that adds to the aggression against noise.” (P4).

3.2.4 Sound environments as temporal markers

The discursive description of the sound environments finally inscribed noise as a strong temporal marker. Participants in particular shared the strong expectation of quiet periods. So much so that one of the residents brought back a calendar as a significant object of her perception of the city’s sound environments: “I brought this: […] it’s a calendar, and I put Sundays in fluorescent, because Sundays are really much nicer, when you open a window in the morning… so here I have all the Sundays in April, and then I have a public holiday, and public holidays are even better than Sundays.” (P10); “On Sunday mornings, the noise from the ring road is reduced by three. you get a feeling of calm.” (P3).

As a result, the noise was described by the participants as even more violent aggression during the periods considered as restful: “The entrance to the MiN for example [national interest market]… lorries coming from the road… Well… there is traffic at 3 am.” (P3); “There will always be traffic, and for the noise, well, there will always be a car passing by and during the night, as there is no traffic, it will pass quickly, it will accelerate.” (P7); “Because between 6 and 7 o’clock in the morning that’s when it takes off the most.” (P2).

3.2.5 How participating in experimentation changes the relationship to sound environments

Another interesting point emerging from the discussion was the modification of relationships to sound environments induced by experimentation, which can be broken down into an increase in technical expertise and a greater sensitivity to societal issues. The use of the smartphone application initially led them to listen to their sound environment in a more conscious way: “Already during the recordings, it’s something quite phenomenal, but the fact of recording opens us up to all the noises around us, so that, on a personal level, it’s rather nice because it reinforces the sense of hearing and listening.” (P8). By measuring sound levels and carrying this careful listening to sound environments over a period of several months, participants learned about ambient sound levels and realized that sound levels were not the only thing shaping their perceptions and feelings. Repeated listening to sound environments lead them to distinguish between sound level and perception: “The first two things that surprised me were the rumor, which was something that had been bothering me for a few years, and then when I measured it I realized that it wasn’t loud, and the noise of the birds, which is really loud in my garden and doesn’t bother me at all.” (P9); “Then another thing, it’s SonoRezé that made me aware of this, it’s the noise of the birds, so a pleasant noise. They are really present, there are a lot of birds.” (P14). If some people are bothered by the noise of a constant rumor, others are more sensitive to the contrast between rumor and emergences: “For me it’s a contrast between silence or very quiet areas, because where I live there are a lot of private houses, it’s rather quiet […], but then there are noise peaks that come. […] I hear, not the ring road, but the road to Pornic I think. And that’s a very diffuse noise, continuous, and it doesn’t bother me much, but I think that the peaks are really not pleasant.” (P4).

This conscious listening initiated by taking measurements also led them to distinguish places that seemed pleasant from a sound point of view, because they were lively and animated: “The whole walking area along Trentemoult because it’s quite noisy but it’s nice noises, even if it’s only the Navibus, it’s a little boat noise, we’re close to the Loire, there are noises of discussions, cheerfulness, it’s lively.” (P8). Other places exposed to low noise intensities seem to be unpleasant to them, because of either the permanence of the noise: “The ring road has been a permanent background noise for the last 2 or 3 years, especially in the morning, and when I measured it, it’s not very loud.” (P9), or the type of noise and the meaning given to it: “I have the impression that all the noises that bother us the most are manufactured noises, not natural noises. It’s things that we are subjected to because it’s traffic, it’s planes… it’s things that are mechanical in fact.” (P2).

For some participants who had a negative perception of their city’s sound environments, taking measurements lead to an awareness of the complexity of sound environments and of the presence of positive sound sources as well: “With the project I started to see the positive noises. Because before I had a very big focus on negative noises. As this app has little buttons for animals, children, I said ok there are positive noises too.” (P4); “Now I am more attentive to unpleasant noises AND a little more attentive to pleasant noises, that’s true. Because before it was the total absence of noise that I considered pleasant, but that is not always the case, there are pleasant noises too.” (P4); “For me, who is on the Avenue Général Leclerc, there are a lot of bicycles that go by and I have to admit that it is a lot quieter than the cars, so it is more pleasant. So that allowed me to highlight the positive points rather than the negative ones.” (P6).

On the other hand, the experiment reinforced negative feelings towards certain sound sources too. This was the case in particular for road traffic and its humming present throughout the territory. For these residents, taking part in the experiment was therefore a possible source of increased annoyance: “Before there was noise, I didn’t pay much attention, now I pay more attention.” (P9); “Since I have the approach in mind, I listen! In fact, I’m becoming obsessed; I can hear the ring road.” (P13); “When I go to people’s houses or when I go to a new place, it’s immediately “can we hear the ring road”… and it’s hellish!” (P2). Some have become aware of the possibility, at a short distance, to access quieter places: “The other time when we did the measurements […] I just had to move 200 m away and I didn’t perceive the noises of this busy street anymore.” (P11). Finally, the participants in the process were able to distinguish the neighborhood unpleasant places because they are noisy: “There is the road to Pornic of course. […] but the road to Pornic is unpleasant because it is very busy.” (P6), and quiet places: “There are peaceful places by the rivers, by the Loire or by the Sèvre, a real treat!”(P2), “Well, these are the two areas that I know well, and they are pleasant because it is very green, the Jaguère there is a small forest and you can no longer see the buildings, there are birds and it is quite calm.” (P4).

3.2.6 Towards the formation of a group of residents empowered to discuss improving the sound environment

Several signals from the participants in the process allow us to perceive the potential of the formation of a group of motivated residents who can increase their expertise on sound environment issues.

First of all, although they are not experts on the subject, they have for them the mastery of use and the search for solutions on a daily basis, sometimes developing strategies to avoid noise: “I ride my bike a lot, so I don’t take my street by bike, I immediately turn off to another one, for my ears, for my safety.” (P1); “It’s obvious, all the main roads are noisy because of the traffic. On the other hand, when I go to the market by bike or on foot, I always manage to go through the back streets that are not busy.” (P5). They show curiosity and reflexivity on the issue of noise: “I wonder if the noise models are accurate. You see the planes directly; there is nothing to stop the noise. On the other side of the street, my house blocks the noise and for the neighbors it’s ok.” (P4), about the phenomena that cause it: “When the winds are dominant you can hear the ring road” (P3); “So when it’s an easterly wind, there’s clearly much more noise. When it’s an easterly wind, we’ll have, for example, the noise of planes landing, which is reduced”(P14), and how it should be taken into account by society: “When I speak with colleagues, they ask me the problem for you is CO ₂ , pollution? I answer no, it’s noise. it is not present in the society I find.” (P4).

There was also a desire to join a collective project. Out of the ten semi-directive interviews conducted after the project, half of the interviewees said they were interested in the subject and the approach, beyond the consideration of their own exposure to noise, and said they were motivated by the fact that they were involved in a common project on their territory of life: “Because I found the subject interesting, and then it’s also a way of participating in the city of Rezé and in what is happening there. I can’t say that it’s a form of commitment because the commitment is weak but there is a bit of that, you can’t just be a spectator, from time to time you have to be an actor too.” (P5); “I was interested in being able to contribute to a common project with a rather original and innovative approach to taking noise pollution into account, a subject that is not necessarily put forward regularly.” (P8).

This participation in a collective encourages a certain empathy among the participants, allowing them to put their personal cases into perspective and to have a more global vision of the noise experience in their city. The latter managed, as passers-by, to adopt the point of view of the residents and even to extrapolate these experiences, in order to develop a collective diagnosis: “I feel sorry for the people next door […] It’s a punctual thing, but it’s repeated many times…” (P3); “I don’t hear them at home but I put myself in the place of the people next door.” (P12); “I can’t imagine the nuisance it will cause to the population” (P11); “I assume that for the people living nearby it must be very impactful.” (P11).

The residents who participated in the process also showed their lucidity regarding the past and current mutations of the city as well as their repercussions on the daily sound environment. Changes have been noted in terms of new forms of mobility: “There is a noise that appeared two years ago, at the beginning, it made me strain my ears all the time. Today it has become THE noise of the city as I have integrated it… it is the noise of the scooter that stops… and then, that looks for where it is going to deliver.” (P10).

The residents described too, through the discourse on noise environments, a changing city, and the burden of rapid urbanization on the sound environments and the lives of the residents: “Very stupidly, I thought that I would escape very quickly to the green by settling here. It’s true that in 15 years this environment has changed a lot […] it was really the old village of Rezé.” (P10); “In Ragon 15 years ago I remember having breakfast outside during the week… and not today!” (P10); “I was very disappointed that the part along the river had been concreted, it could have become a very beautiful green area. But 12 or 15 years ago it was not yet on the agenda, we concreted more than we greened the cities.” (P5).

The last point, which concerns local issues and actions to be taken, drew a portrait of residents educated in health issues and practices that lead to sound environments of quality: “That was my question too, how bad is the noise? This permanent background noise or this instantaneous noise?” (P3), and aware of practices that lead to sound environments of quality: electric vehicles, silent pavements, residential areas. Although it is not possible to know whether this knowledge preceded the experimentation, this point suggests an educated debate on the possible mitigation of noise using innovative materials or a certain design of the space: “Electricity is great for that, for noise it can change a lot of things.” (P7); “They now use a form of surface coating. when you drive by it’s much quieter all of a sudden… have you noticed that?” (P7);” I confirm I live in a housing estate, you come in from a street, a roundabout, you come out from the same place, as soon as you’re behind you don’t hear anything. There is no passage.” (P9); “For me, the main axis that could make the sound evolve in the city is really not to do 100% road.” (P8).

These discussions were also the place to question the elected representatives present on certain elements, such as urban planning rules, which are perceived as an injustice in the face of noise: “Who accepts building 20 m from the ring road? I mean, come on!” (P3); or to show legislative inconsistencies in their view of noise management: “We wonder why it’s forbidden to use the lawnmower in the garden on Sundays, and why planes can fly.” (P4). Finally, the fight against noise requires, according to the participants, a collective awareness and a modification of mobility practices: “For me, we are responsible for this, as citizens. it is our way of life that creates this noise…”, (P2) “I’m happier riding a bike than driving a car in the city. I’m always on time for my appointments, it doesn’t cost me anything, I don’t make any noise, I do some sport…”, (P2); “We must discourage people from taking their car” (P2).