宮城教育大学 環境教育研究紀要

第 15 巻 (2013)

Urban vs. Natural Sounds in Sendai city : A Comparative Study
Lazaro M. Echenique-Diaz and Chiemi Saito*
Abstract ： In an attempt to characterize the soundscape in areas of Sendai City, we have studied
sound pressure levels at 9 different points differing in degree of urbanization and representing different
sound environments. Results indicates that larger sound amplitudes in each site correspond to thenature of its environment. In urban zones with few natural elements, manmade sounds are the mostintense, and areas with less degree of urbanization or a more natural environment, the predominantsounds were all natural except in case of sound contamination from a loud source such as a helicopter
flying in the distance.
Keywords : natural sounds, soundscape, urban, sound amplitude

1. Introduction

2. Materials and Methods

The amount of urban vs. natural sounds that weRecording points were only a few compared to theexperience on daily basis is an interesting question

diversity of environments associated with Sendai City

seldom addressed in environmental education studies(Fig. 1). Five different environments were chosen ini n t he To ho ku are a, no r t he as t J ap an, a d y n a m i csuburban and urban areas (Fig. 2). Points 1 and 2 aresocioeconomic region where cities are constantly

within local University campuses with scattered trees

growing and changing. As in every other place on earth,around them and relatively close to large patches ofcities in this region grow by drastically changing theforests. Points 4 and 5 are within large forested patches

natural landscape, and the soundscape associated withand relatively close to streams. Points 5 to 7 are in thenatural spaces changes along as these are absorbed bydowntown of the city, around and at Sendai Station.

the urbanization process. This change in the soundscape

Point 8 in a residential area in the suburbs, and point 9

associated with urbanization has proven to havein a suburban paddy rice field (see details in Table 1).

important biological and evolutionary consequences inRecordings were performed with an Olympus PCM

birds adapting to live in urban areas (Potvin et al., 2010),

recorder (SL-11) and a LiSN parabolic microphone (Fujiand may also affect our perception of concepts associatedPlanning Co., http://www.din.or.jp/~fpc/Ls/indexLs.htm)

with sounds such as “noise”and“quiet”(Echenique-for 3 to 5 minutes between 7:00 and 9:00 am at points

Diaz and Saito, 2010). In order to compare the dominant

1 to 7, and between 7:00 and 8:00 pm at points 8 and 9,

sounds in areas with different degrees of urbanization, weacross 4 months (May to August) in 2011. We chose tohave carried out a preliminary study of the soundscapealways point the parabolic microphone to the north inin Sendai city, and report here our results with a brief

every recording point, and hold it about 1.5 m from thediscussion of its implications.

ground.
Recordings were visualized in Audacity 2.0.3, a noncommercial, freely available software popular among* Environmental Education Center, Miyagi University of Education－ 69 －Urban vs. natural sounds in Sendai city : a comparative study

music lovers, but equally useful in the edition andfor animals to easily wander around these areas. In thesimple analysis of any kind of sound. A simple editioncase of point 1 for instance, at the time of the recording a

was performed as follows: the first 15 seconds of eachmasked palm civet (Paguma larvata) was spotted walking

recording was cut to eliminate any noise resulting frombetween buildings. At point 2 a chorus of frogs totally

movements of the recording person, leaving one minutedominated the soundscape even though there were someof recording intact and deleting the rest. Therefore,

car sounds in the background. It is possible that givenedited recordings were left at 1 minute of length. In thethat the fountain found in this park is the only water body

analysis, sound amplitudes relative to the frequency

in a hundred meters radio around it, a higher than usualcomponents in each recording as a measure directly

density of frogs resulted in a lauder sound. However,related to the acoustic energy or intensity of a sound was

saturation in this track may be the result of a recording

obtained from Plot Spectrum analysis, where the selected

done too close to singing frogs using a parabolic

audio (which is a set of sound pressure values at points in

microphone. In this regard, in 3 occasions when citizenstime) is converted to a graph of frequencies (given in Hz

were played these recordings, sounds from points 1 andin the x axes) against amplitude (given in decibels, dB, in

2 were considered as“nice”but very noisy, and thatthe y axes). The nature (urban or manmade vs. natural)from point 5 as simply“very noisy”. However, pointof the dominant sound (showing the largest amplitude)

5 is a recording inside a moving bus, a soundscape thatin each recording site was determined to compare thewe experience normally in our lives, and that doesn’tsoundscape in each point.

seem to irritate that much. In fact, Japanese people pricesilence inside a bus (not talking) even though this isChanges in the soundscape relatively to season changes

already a very noisy ambient per se. On the other hand,(for instance, different type of animals singing from lateat point 7 in the downtown of Sendai, on the 31st floor in

spring to summer) were ignored in this preliminary

AER building, a quiet environment where people talking

report given that our goals were to document andwere the dominant sound, the soundscape was still full ofcompare sound pressure levels and the nature of thecar sounds, despite the height at which it was recorded.

sounds (natural vs. manmade) at any given time in

In general, the 9 recordings in our study show a clear

different parts of the city.

trend where natural sounds are dominant in sites awayfrom the urbanized areas. This seemingly obvious result

3. Results and Discussions

is in fact an indicator that our modern lifestyle disconnect

Dominant sounds that were urban or manmade in nature

us form nature, where we create our own environment,in this study were found at points 4 to 8 (Table 2, Fig.

with its own unnatural soundscape that ends up being

3). Among these, point 4 was in a large patch of forest

the norma. We believe that in order for Environmental

relatively isolated form the more urbanized areas ofEducation in the XXI century to change and generate

Sendai. However, the sound of a helicopter flying in the

new attitudes towards nature, this disconnection should

distance totally dominated the soundscape here evendisappear.

though some forest birds were also singing. Naturalsounds dominating the soundscape were found in theAcknowledgment

remaining recording points. Points 1 and 2 are located at

This study was supported by Grant-in-Aid for Youngplaces where usually urban sounds predominates (cars,Scientists B (22730682).

construction machinery, etc.), however, the presence oftrees and closeness to forested patches makes it possible－ 70 －

宮城教育大学 環境教育研究紀要

References

第 15 巻 (2013)

Po t v i n D . , Pa r r i s K . M . a n d M u l d e r R . A . (2010) .

Echenique-Diaz L.M. and Saito C. (2010). Bioacoustics asGeographically pervasive effects of urban noise ona tool for Environmental Education. Research Bulletinfrequency and syllable rate of songs and calls inof Environmental Education center, Miyagi University

silvereyes (Zosterops lateralis). Proceeding of the Royalof Education, 12: 41- 48.

Society, Series B. DOI: 10.1098/rspb.2010.2296.

Table 1: Recording points around Sendai City.

Point

Description

1

Parking lot in Kawauchi campus, Tohoku University

2

Park in front of Miyagi University of Education COOP

3Stream in the forest in Kadan

4

Aoba no Mori (the forest of Aoba Hill)

5

Inside a bus at Aoba Avenue

6

In front of Sendai Station

7

AER building’s observation deck, 31st floor

8

Yoshinari 1 chome residential area

9

Rice fields next to Saikachi Dam, Nishikigaoka

Table 2: Peak amplitude for recordings at points 1 to 9 around Sendai City, and the nature of the sound corresponding to that
amplitude (natural* or manmade).

Point

Peak amplitude

Corresponding sound1-39.2 dB

Cicada*2-17.4 dB

Frogs*

3-30.6 dB

Forest birds*4-17.2 dB

Helicopter pass

5-14.0 dB

Bust stop announced on speakers

6-12.1 dB

Car sounds

7-30.9 dB

People talking

8-11.5 dBCar pass

9- 32.5 dB

Frogs*－ 71 －Urban vs. natural sounds in Sendai city : a comparative study

Figure 1. Sendai City on the northeast of Japan.

Figure 2. Recording points around Sendai City.

－ 72 －宮城教育大学 環境教育研究紀要

Point 1

Point 2

Point 3

Point 4

Point 5

Point 6

Point 7

Point 8

Point 9Point 3 spectrogram (fragment)

第 15 巻 (2013)

Point 4 spectrogram (fragment)

Figure 3. Plot Spectrum of recordings at points 1 to 9 around Sendai City, and two spectrogram fragments for point 3 (forestbirds singing) and 4 (helicopter pass and forest birds singing). In the Plot Spectrum the higher peak value in the y axes
(amplitude) was taken as the maximum amplitude reported in Table 2. In the spectrograms, the closer the color gets to white,
the larger the amplitude. At point 3, birds dominate the soundscape. At point 4, a helicopter sound is dominant.

－ 73 －