The perceived quality of soundscape in three urban parks in Rome

The perceived quality of soundscape in three urban parksin Rome

Giovanni Brambilla and Veronica GalloCNR-IDASC, Institute of Acoustics and Sensors “O. M. Corbino,” via del Fosso del Cavaliere 100,00133 Rome, Italy

Francesco Asdrubalia) and Francesco D’AlessandroCIRIAF, Interuniversity Research Center on Pollution from Physical Agents, University of Perugia,Via G. Duranti 67, 06125 Perugia, Italy

(Received 4 May 2012; revised 29 March 2013; accepted 11 April 2013)

The present paper reports a socio-acoustic survey carried out in three large urban parks in Rome,

selected on the basis of the outcome of a preliminary online survey. According to the experimental

protocol applied in a previous study carried out in Milan and Naples, binaural recordings in 85 sites

and interviews with 266 users of the three parks were performed only during the day in summer-

time. On the basis of selected acoustical descriptors, the sonic environment of the three parks was

categorized and, thanks to statistical analysis, three clusters were identified. The results confirm

that the sound environment in urban parks is often considered as “good” or “excellent” even if the

sound pressure level is nearly always higher than the limits commonly used to define quiet areas.

This is due to the influence of other factors, such as the presence of trees, natural features, and the

tranquility; all of these components cannot be neglected in the assessment of the soundscape

because they directly affect the psychological state of the person.VC 2013 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4807811]

PACS number(s): 43.50.Qp, 43.50.Rq, 43.50.Sr [KML] Pages: 832–839

I. INTRODUCTION

The Directive 2002/49/EC of the European Parliament

and of the Council relating to the assessment and manage-

ment of environmental noise introduces the concept of “quiet

areas,” either inside agglomeration or in open country.

However, criteria based on measurements to identify such

areas have not been defined yet, mainly due to the lack of

knowledge of the effect of noise on the perceived sound-

scape quality.1

Several studies have been carried out over the last dec-

ade showing that for the analysis of the perception of the

sonic environment quality a multidisciplinary approach is

more appropriate rather than focusing on cumulative noise

indicators only, i.e., the equivalent sound pressure level

(LAeq) or the day-evening-night level (Lden).2,3 This holistic

approach should take into account the several non-acoustical

features characterizing the “quiet areas,” such as visual and

microclimate aspects, which may interact with auditory

judgements and, therefore, influence the evaluation of the

perceived quality of these environments. For instance, the

interaction between audio and video in quiet areas has been

investigated and an engineering model for the “tranquility”

as a function of the noise level and proportion of the natural

features has been proposed.4

The importance of “quiet areas” is widely recognized

as they provide, at least temporarily, opportunities for a

feeling of relaxation, calm and recovery from noise

pollution to which the population is exposed in everyday

life.5,6 This essential health-promoting function should be

preserved and improved, especially for the urban parks, as

they can be easily accessed by the users but, at the same

time, they are often surrounded by noisy areas due to the

sound emission of road traffic, industries, and other sources.

In particular, the extent of the park has an important influ-

ence on the maximum tranquility that can be achieved due

to effects of distance in reducing traffic noise immission

from the boundary roads and the provision of a high per-

centage of natural features.7

A review of the literature of studies carried out in Italy

on soundscape of potentially quiet areas8 has shown that

only few of these included noise monitoring and interviews

to people to know their ratings on the various aspects of the

environment. These studies were performed mainly in urban

parks in Naples and in Milan.9

This paper describes a socio-acoustic survey carried out

in three urban parks in Rome aimed to investigate the users’

perception of the environment quality in the parks, including

the sonic one, and its relationship with selected acoustical

parameters. The study is the first performed in the urban

green areas in Rome and its structure and methodology is

comparable with the previous surveys carried out in urban

parks in Naples and Milan.9

A preliminary survey on the web was performed to

tune the questionnaire to be used in the field and to iden-

tify the parks to be investigated. The in situ surveys were

carried out taking binaural recordings of the sonic environ-

ment and simultaneous interviews to people in the park.

Additional analyses were performed in order to relate the

a)Author to whom correspondence should be addressed. Electronic mail:

[email protected]

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survey data with the acoustical parameters determined

from the recordings.

II. SELECTION OF THE URBAN PARKS

A preliminary survey was performed to identify the

most frequented urban parks in Rome and to assess other

aspects of these areas. In order to quickly reach an adequate

number of subjects, the survey was carried out on the web

by a questionnaire containing 15 questions and sent via

e-mail to people living in the Municipality of Rome. The

questionnaire was available on the web for 15 days and 121

people responded.

The questions dealt with several items, among which

the most frequented parks, the most pleasant and unpleasant

ones, the reason for going to the park, the degree of satisfac-

tion of the sonic environment and of the area considering

other aspects, such as vegetation, air pollution, security,

cleanliness, and so on.

Based on the outcomes of this poll, the urban parks of

Villa Pamphili (P), Villa Borghese (B), and Parco Caffarella

(C) were selected for the field survey because they were the

most visited. They have a wide extension with different

areas and uses. Furthermore, they have different locations

within the urban area (Fig. 1). In particular they were usually

frequented by 17%, 13%, and 7% of respondents, respec-

tively. It is interesting to point out that the main reason to be

in a park was walking or sport for 37% of respondents and

tranquility was chosen only by 3%. Looking at the corre-

sponding data obtained for the three selected parks, Villa

Pamphili is mainly frequented for walking or sport (53% of

respondents), whereas at Parco Caffarella 14% of respond-

ents look for tranquility.

Villa Pamphili (180 hectares) is one of the best pre-

served parks; the main change from the past is a busy road

dividing the park into two parts. There are natural zones, not

easily accessible (less visited), and areas close to the entran-

ces of the park which are the most used. There are two play-

grounds, a bar, a location for sports facilities and a large area

for dogs.

Villa Borghese (about 80 hectares) is one of the most fa-

mous parks in Rome, it is well known worldwide and located

in the city center. It is enriched by the presence of historical

and architectural buildings and, therefore, it is frequented by

tourists and often hosts exhibitions and concerts. The sonic

environment is characterized by anthropic sounds and traffic

noise from the vehicles passing-by on the streets surrounding

and crossing the park.

Covering over 190 hectares, Parco Caffarella owes its

cultural and historical feature to its location, close to two

main ancient roads: Appia Antica and Latina. Its structure

differs from the other parks showing natural features mainly.

It is usually frequented by the residents in the area, mainly

for jogging, cycling, and by kids for the play areas. Natural

sounds are predominant in the sonic environment, even if

aircraft noise is perceived due to the fly-overs from/to

Ciampino airport.

After the selection of the three parks, thanks to on-site

inspections, personal experience of authors and cooperation

with park managers, useful information was gathered to

identify zones and/or paths with homogeneous uses (i.e.,

play grounds, sport activity, etc.) and most frequented by

users.

III. FIELD SURVEYS

The sonic environment in each of the identified zones in

the three parks was recorded binaurally in fixed positions

distributed as widely as possible to cover the entire areas

open to the public. This procedure was preferred to sound-

walks to avoid sounds by the operator’s steps. The record-

ings were made for periods of about 5 min, using binaural

FIG. 1. Location of the three selected

parks in Rome.

J. Acoust. Soc. Am., Vol. 134, No. 1, Pt. 2, July 2013 Brambilla et al.: Soundscape of urban parks in Rome 833


headphones worn by the operator and connected to a digital

audio recorder [Fig. 2(a)]. Table I reports the number of sites

in each park where recordings were made. During the cali-

brated recordings, noticeable sound events and the corre-

sponding sound sources were noted by the observer for post-

processing analysis.

The binaural recordings have been analyzed to deter-

mine selected acoustical parameters, namely, LAeq, statistical

levels LAn, the unweighted spectrum center of gravity G,10

proposed as a good measure for the degree of pollution of

the soundscape with traffic noise,11 the number of sound

events exceeding LA50 by 3 dBA and the number of emerg-

ing peaks identified by the 5 dBA exceedance of LA90, as

well as psychoacoustic descriptors more related to the sound

perception (loudness, sharpness, roughness, and fluctuation

strength). The detailed list of the acoustical parameters cal-

culated from the binaural recordings is reported in Table II.

Before such analysis, occasional sound events not usually

present in the sonic environment, such as temporary work

sites, and so loud as to affect the measurement, have been

eliminated in the calculation of noise descriptors.

Face to face interviews were carried out simultaneously

with the sound recordings (Table I) by means of a question-

naire adapted from that used in the preliminary online poll.

The interviewees were selected randomly and when on the

spot more than one person was present, only one was picked

out [Fig. 2(b)]. Sixteen questions were asked to collect infor-

mation on the following items:

(1) presence of the interviewees in the park (monthly fre-

quency, days of the week, hours, and average time of

attendance) in terms of potential multiple answers to be

chosen among proposed options;

(2) the main reason for frequenting the park (open answer);

(3) the degree of satisfaction of the area as a whole and of

its sonic environment, given on a 5 point scale from 1

(not at all satisfied) to 5 (very satisfied);

(4) the assessment of the quality of 20 features of the area,

expressed on a scale from 1 (very poor) to 10 (very

good);

(5) indication of the sounds mostly heard in the park and

those wished to be heard (open answers);

(6) interviewee’s personal information (age, educational

level, occupation) and indication of her/his most fre-

quented areas or paths in the park.

The acoustic monitoring and the interviews were per-

formed in July and September 2010, on weekdays and on

Saturdays during daylight period, sunny weather and with no

or light wind. In the chosen periods the parks were largely

frequented due to the hot weather and schools closed; the

month of August was excluded since it is a holiday period

for most Italians.

In order to categorize the parks on the basis of their

sonic environment, the acoustical data determined for

each channel of the 82 collected binaural recordings

were considered. Since all the data had different mea-

surement units, their normalization was required in order

to proceed to the cluster analysis. In particular, the min–-

max normalization was applied to obtain the transformed

value xt of the selected input variables x in the range

C – D:

xt ¼x� xmin

xmax � xmin

� �� ðD� CÞ þ C;

FIG. 2. Example of operators during

the binaural registration (a) and the

interviewing survey (b).

TABLE I. Binaural recordings and interviews carried out in the three parks.

Park N. recordings N. interviews

Villa Pamphili 31 79

Villa Borghese 29 88

Parco Caffarella 22 61

Total 82 228

TABLE II. Set of the acoustical parameters determined for each channel of

the binaural recording.

Continuous equivalent level Leq [dB], [dBA]

Sound pressure level percentiles [dBA]

LA5, LA10, LA50, LA90, LA95

Sound pressure level Lmin, Lmax [dBA]

Standard deviation of sound pressure level [dBA]

1/3 octave band spectrum Leq [dB]

Centre of gravity G of the 1/3 octave band spectrum between 80 and 8000 Hz

Number and duration of events (>1 s) above LA50þ 3 dBA

Number of emerging peaks above LA90þ 5 dBA

Loudness N [sone]

Roughness R [asper]

Sharpness S [acum]

Fluctuation strength F [vacil]

834 J. Acoust. Soc. Am., Vol. 134, No. 1, Pt. 2, July 2013 Brambilla et al.: Soundscape of urban parks in Rome


where C¼ 0 and D¼ 1 were chosen. The input variables

were the LAeq level, the noise climate LA10 – LA90, the per-

centile LA50, the 5th percentile of loudness N5, the mean val-

ues of sharpness S, roughness R, fluctuation strength F, and

the unweighted spectrum center of gravity in terms of lg(G).

The hierarchical cluster analysis was performed by means of

the IBM SPSS Statistics software, applying Ward algorithm

for agglomerative clustering, squared Euclidean distance,

and selecting the single solution of three clusters in order to

distinguish the three parks. To determine the significance of

the input variables in the clustering agglomeration, the

ANOVA was also performed. To validate the output of this

clustering, the k-means procedure was applied considering

three clusters and setting as initial centroids those obtained

from the previous hierarchical cluster analysis.

IV. RESULTS AND DISCUSSION

A. Acoustical data

According to the current Italian legislation, quiet areas

are included in the most sensitive acoustic zone, for which

the outdoor LAeq level referred to day-time period (06–22 h)

must not exceed the 50 dBA limit. Looking at the LAeq data

measured in the three parks, reported in the bean plot12 in

Fig. 3, most of the values in the Pamphili and Borghese

parks (87% and 93%, respectively) are above the noise limit

(dashed line in Fig. 3), whereas in Caffarella the majority of

sound recordings (54%) are below 50 dBA. The bean plot in

Fig. 3 shows the distribution of LAeq (left side) and LA95

(right side) values for each park. The smallest variability is

observed for Borghese (LAeq standard deviation s¼ 3.2

dBA) and the largest occurs for Caffarella (LAeq standard

deviation s¼ 5.4 dBA), which is close to the value observed

for Pamphili (LAeq standard deviation s¼ 5.0 dBA). In

Borghese park the LAeq and LA95 values are close to a nor-

mal distribution, whereas in Pamphili and Caffarella the dis-

tributions are not normal.

Similar results have been obtained for parameters more

related to the hearing perception, such as the 5th percentile

of loudness N5, a descriptor highly correlated with the per-

ceived total loudness in case of unsteady sounds,13 the me-

dian value of loudness, N50, and the ratio N5/N50 in

percentage.14

FIG. 3. Bean plot of the measured LAeq and LA95 levels in the three parks

and noise limit required for the daytime LAeq by the Italian legislation

(dashed line).

FIG. 4. Center of gravity of the spectrum lg(G) of the sonic environments

versus LA50.

FIG. 5. Probability density function of SEL of

three categories of sound events exceeding the

threshold LA90þ 5 dB observed in each park

(P¼Pamphili, B¼Borghese, and C¼Caffarella).



The above outcomes show that, according to acoustic

data only, wide areas of the three parks should not be consid-

ered so “quiet” and, therefore, this might concur to reduce

the function of the park as far as relaxation and calm is

concerned.15

Among the acoustical parameters, the median value of

the sound pressure level in dBA, that is LA50, has been

observed to be a better predictor for quietness rather than

LAeq.11 This statistical level has been contrasted with the

unweighted spectrum center of gravity G as formulated by

Raimbault,16 an acoustic measure of the spectral content of

the soundscape, calculated according to the following

formula:

G ¼

Xi

½10Li=10 � Bi�X

i

½10Li=10�;

where Li is the unweighted sound pressure level in dB, meas-

ured for each third octave band-width Bi from 80 Hz to

8 kHz. The lg(G) data are plotted in Fig. 4 versus LA50,

which is less sensitive to peaks in the sound pressure level

than LAeq.

The dashed lines in the plot, corresponding to

LA50¼ 50 dB and lg(G)¼ 2.1[log(Hz)], satisfactorily distin-

guish the three sonic environments of the three parks. As

shown in Fig. 4, 77% of recordings taken at Caffarella are in

the same region (A in the plot), 81% of those made at

Borghese are in region B and 63% of those taken at Pamphili

are within region C.

It is worth pointing out that the sound events perceived

in the three parks are numerous and produced by several

types of sources, from natural to anthropogenic and techno-

logical ones, such as vehicle pass-by, aircraft fly-over, and

so on. For instance, Fig. 5 shows the probability density

function of the SEL values of events exceeding the threshold

of LA90þ 5 dB for each park. In each subplot the median

value of SEL (~x) and the percentage of events of the same

type (referred to the total observed in the same park) are

reported. In Borghese park the anthropogenic events are pre-

dominant, whereas in the other two parks the technological

events are more frequent and in Caffarella these events show

SEL values lower than in Pamphili.

Regarding the categorization of the parks on the basis of

the acoustical descriptors of their sonic environment, the

ANOVA showed that all the eight input variables were sig-

nificant for clustering (at 0.05 significance level). As shown

in Table III, 86% of recordings taken in Borghese is in the

obtained cluster 1, 86% of those in Caffarella is in cluster 3,

whereas the recordings taken in Pamphili are distributed

among the three clusters and the largest percentage (44%) is

in cluster 3. The plot in Fig. 6 reports the distribution of

lg(G) data versus the percentile N5 of the loudness for the

three obtained clusters, being the latter descriptor highly cor-

related with the perceived total loudness in case of unsteady

sounds.11 The separation of the clusters pointed out by the

dashed lines, corresponding to N5¼ 12 sone and lg(G)¼ 2.7,

performs better than the previous values of LA50¼ 50 dBA

and lg(G)¼ 2.1 (Fig. 4), leading to the percentages of correct

identification shown in the plot.

B. Subjective ratings data

In this section the main results obtained by the analysis

of subjective responses collected from the 228 people inter-

viewed are reported.

Figure 7 shows the distribution of the age of respondents

among the three parks. The largest group (21%) was older

than 65, followed by people in the 35–45 yr old range (19%).

FIG. 6. Clustering of recordings plotted as function of percentile N5 of loud-

ness versus spectrum center of gravity lg(G).

TABLE III. Comparison between clustering of recordings and the “a priori”

classification based on belongings of sites to the three parks.

A priori classification

Cluster Pamphili Borghese Caffarella

1 15 (24%) 50 (86%) 0 (0%)

2 20 (32%) 0 (0%) 6 (14%)

3 27 (44%) 8 (14%) 38 (86%)FIG. 7. Distribution of the respondents’ age.



Males (52%) were slightly higher than females (48%). In

addition 53% of respondents frequented the parks more than

four times a month and their largest fraction (41%) reported

to be in the park for a period between 1 and 2 h. Because of

these results, it is likely that the ratings provided by the sub-

jects are outcomes of their consolidated experience of the

park rather than occasional ones.

The percentages of answers dealing with the most per-

ceived sound [Fig. 8(a)] and that most desired to be heard

[Fig. 8(b)] in each park show the highest values for sounds

from nature. These data show that the sonic environment sat-

isfactorily matches the expectation and experience of users

of the parks, factors influencing the perception of sound-

scape quality.17

For each park Fig. 9 shows the average score given on

the quality of the 20 aspects to be evaluated. Taking scores

greater or lower than 6 (gray line in Fig. 9) as positive and

negative appraisal respectively, the ratings were positive for

only eight aspects for all the parks. The presence of trees

(average score 8.2 across parks) and tranquility (average

score 8.0) were judged better than natural sounds (average

score 7.7) and silence (average score 7.6). The aspects refer-

ring to facilities and their maintenance were often negatively

judged in all the parks.

Regarding the perceived quality of both sonic and over-

all environment, the score 4 and 5 given on scale from 1 to

5, were considered as positive ratings. Pooling these scores

for each park, the corresponding percentages of respondents

are plotted in Fig. 10. For Caffarella 88% of people gave a

positive rating on the perceived quality of sonic environ-

ment, a value greater than that established by the Swedish

Environmental Protection Agency18 to identify a “quiet

area” (80%). In addition, the quality of the sonic environ-

ment was rated better than that of the area including other

aspects only for this park, whereas Borghese showed a simi-

lar percentage for both the qualities. It has to be noted that

FIG. 8. Sounds perceived (a) and desired to be heard (b) in the three parks.

FIG. 9. Average ratings on the quality of 20

aspects of the parks.



the differences between the average scores given to the qual-

ity of the sonic and of the overall environment are statisti-

cally significant.

C. Relationships between subjective ratings andacoustical data

Some of the answers given to the question dealing with

the most frequented area/path of the park were too generic

and, therefore, in these cases it was not possible to straight-

forwardly associate the interviewees to specific sites where

binaural recordings were taken. Where the area/path indi-

cated as most frequented was large and/or included more

than one measurement site, than the average values of the

acoustical parameters of the recordings taken in the sites

inside that area were considered. These mean values were

used to analyze their relationship with the corresponding

questionnaires associated at the same area/path. Table IV

reports the number of questionnaires associated to recording

sites for each park. For Villa Borghese the table also reports

the data collected in a further study in three sites. This study

was performed in July 2011 with the same experimental pro-

tocol as the previous one. People present in the surroundings

of each site were interviewed in order to match as closely as

possible their sound exposure with their answers to the ques-

tionnaire. The average age of the 38 subjects was 34 yr. The

largest percentage of subjects (34%) reported to be in the

park from 1 to 2 h and 53% frequented the park at least twice

a month.

The responses on perceived quality of the overall and

sonic environment were compared with those of the previous

survey in the same park. The data do not show statistically

significant differences at 95% level. Pooling the scores 4

(satisfactory) and 5 (very much satisfactory) given on the

perceived quality, Fig. 11 shows the corresponding percen-

tages of respondents plotted versus the 5th percentile of

loudness for all the questionnaires associated to acoustical

data, namely, 104 interviews linked to 10 groups of record-

ing sites inside Villa Borghese. Looking at the linear regres-

sion lines, as expected, the perceived quality of the sonic

environment decreases with increasing of loudness N5,

namely, a decrease of about 6% in the degree of satisfaction

for an increase of every 1 sone. Such quality is much better

related to N5 (r¼�0.71) than that of the area as a whole

(r¼�0.12). For the latter a less steep slope (about 1% for

every 1 sone), is observed. Because the quality of the area as

a whole has no strong correlation with the perceived loud-

ness, it may be inferred that non-acoustical parameters pre-

vail in the overall judgment of the area. This seems to be

FIG. 10. Overall assessment of the area versus its sonic environment for the

three parks.

TABLE IV. Groups of sites where interviews were associated to mean values of acoustical parameters.

No. of interviews and no. of sites of the three parks

Pamphili Borghese Caffarella

Area of the park Interviews Sites Area of the park Interviews Sites Area of the park Interviews Sites

A 3 1 A 4 1 A 3 1

B 3 2 B 4 2 B 4 3

C 4 1 C 4 3 C 6 2

D 4 2 D 5 2 D 7 1

E 5 1 E 7 2 E 7 2

F 5 2 F 11 1 — —

G 18 2 G 11 1 — —

— — H 16 1 — —

— — I 20 6 — —

— — L 22 3 — —

FIG. 11. Perceived quality of the sonic environment and of the area as a

whole versus the 5th percentile of loudness N5.



confirmed by the results in Fig. 9, which show that Villa

Borghese, even though presents the highest sound pressure

levels among the three parks (see Fig. 3), obtained the high-

est score on vegetation and high scores on natural sounds

and tranquility.

V. CONCLUSIONS

Urban parks are important for promoting and preserving

health, but they are often under flight paths or surrounded by

noisy areas, such as roads, railways, and industries.

The paper describes a socio-acoustic survey carried out

in three urban parks in Rome aimed to investigate the users’

perception of the acoustical quality in the parks and its rela-

tionship with selected acoustical parameters.

The analysis of the data collected in the three urban

parks shows that the sound environment is perceived as good

(34%) and very good (40%), even though the three areas

should not be considered “quiet” because in most of the sites

the value LAeq¼ 50 dBA is exceeded. In addition several

events due to different noise sources are also observed in the

three parks.

The correlation between the logarithm of the center of

gravity of the unweighted spectrum lg(G) and the 5th per-

centile N5 of the loudness seems to be adequate in discrimi-

nating the sonic environment, according to the clustering

obtained on the basis of the considered eight acoustic

descriptors. In particular the thresholds of lg(G)¼ 2.7 lg(Hz)

and N5¼ 12 sone provide correct identification of more than

92% of cases in the three clusters.

On the other hand, as said before, users seem to appreci-

ate both the sound environment and the general conditions

of the parks. The results are confirmed by further analysis

conducted in three selected sites of Villa Borghese, where

the presence of vegetation and natural sounds seem to have

more influence on the perceived quality of the sound envi-

ronment than the measured sound pressure levels. Non-

acoustical parameters, therefore, seem to prevail in the over-

all judgment of a park area. The classic approach based

exclusively on the use of the A-weighted equivalent sound

pressure level is not sufficient to describe the quality of a

sound environment, also considering that the noise limits

issued by the legislation so far are aimed to reduce the harm-

ful effects of noise on health. They would not be probably

suitable for areas fulfilling a recovery and health-promoting

function as urban parks. In such areas the importance of sub-

jective aspects, such as expectation and motivation, are cru-

cial and they should be taken into account for their

preservation and improvement.

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Documents

The perceived quality of soundscape in three urban parks in Rome