Echenique-Diaz Lazaro M.

Saito Chiemi

Miyagi University of Education Repository

宮城教育大学機関リポジトリUrban vs. Natural Sounds in Sendai city : AComparative Study著者 Echenique-Diaz Lazaro M., Saito Chiemi雑誌名 宮城教育大学環境教育研究紀要巻 15ページ 69-73発行年 2013-03URL http://id.nii.ac.jp/1138/00000953/－ 69 －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 StudyLazaro 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 the nature of its environment.  In urban zones with few natural elements, manmade sounds are the most intense, and  areas with less degree of urbanization or a more natural environment, the predominant sounds 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* Environmental Education Center, Miyagi University of Education1.  IntroductionThe amount of urban vs. natural sounds that we experience on daily basis is an interesting question seldom addressed in environmental education studies in the Tohoku area, nor theast Japan, a dynamic socioeconomic region where cities are constantly growing and changing. As in every other place on earth, cities in this region grow by drastically changing the natural landscape, and the soundscape associated with natural spaces changes along as these are absorbed by the urbanization process. This change in the soundscape associated with urbanization has proven to have important biological and evolutionary consequences in birds adapting to live in urban areas (Potvin et al., 2010), and may also affect our perception of concepts associated with sounds such as  “noise” and “quiet” (Echenique-Diaz and Saito, 2010). In order to compare the dominant sounds in areas with different degrees of urbanization, we have carried out a preliminary study of the soundscape in Sendai city, and report here our results with a brief discussion of its implications.  2.  Materials and MethodsRecording points were only a few compared to the diversity of environments associated with Sendai City (Fig. 1). Five different environments were chosen in suburban and urban areas (Fig. 2). Points 1 and 2 are within local University campuses with scattered trees around them and relatively close to large patches of forests. Points 4 and 5 are within large forested patches and relatively close to streams. Points 5 to 7 are in the downtown of the city, around and at Sendai Station. Point 8 in a residential area in the suburbs, and point 9 in a suburban paddy rice field (see details in Table 1). Recordings were performed with an Olympus PCM recorder (SL-11) and a LiSN parabolic microphone (Fuji Planning Co., http://www.din.or.jp/~fpc/Ls/indexLs.htm) for 3 to 5 minutes between 7:00 and 9:00 am at points 1 to 7, and between 7:00 and 8:00 pm at points 8 and 9, across 4 months (May to August) in 2011. We chose to always point the parabolic microphone to the north in every recording point, and hold it about 1.5 m from the ground.  Recordings were visualized in Audacity 2.0.3, a non-commercial, freely available software popular among － 70 －Urban vs. natural sounds in Sendai city : a comparative studymusic lovers, but equally useful in the edition and simple analysis of any kind of sound. A simple edition was performed as follows: the first 15 seconds of each recording was cut to eliminate any noise resulting from movements of the recording person, leaving one minute of recording intact and deleting the rest. Therefore, edited recordings were left at 1 minute of length. In the analysis, sound amplitudes relative to the frequency components in each recording  as a measure directly related to the acoustic energy or intensity of a sound was obtained from Plot Spectrum analysis, where the selected audio (which is a set of sound pressure values at points in time) is converted to a graph of frequencies (given in Hz in the x axes) against amplitude (given in decibels, dB, in the y axes).  The nature  (urban or manmade vs. natural) of the dominant sound (showing the largest amplitude) in each recording site was determined to compare the soundscape in each point. Changes in the soundscape relatively to season changes (for instance, different type of animals singing from late spring to summer) were ignored in this preliminary report given that our goals were to document and compare sound pressure levels and the nature of the sounds (natural vs. manmade)  at any given time in different parts of the city. 3.  Results and DiscussionsDominant sounds that were urban or manmade in nature in this study were found at points  4 to 8 (Table 2, Fig. 3). Among these, point 4 was in a large patch of forest relatively isolated form the more urbanized areas of Sendai. However, the sound of a helicopter flying in the distance totally dominated the soundscape here even though some forest birds were also singing. Natural sounds dominating the soundscape were found in the remaining recording points. Points 1 and 2 are located at places where  usually urban sounds predominates (cars, construction machinery, etc.), however, the presence of trees and closeness to forested patches makes it possible for animals to easily wander around these areas. In the case of point 1 for instance, at the time of the recording a masked palm civet (Paguma larvata) was spotted walking between buildings. At point 2 a chorus of frogs totally dominated the soundscape even though there were some car sounds in the background. It is possible that given that the fountain found in this park is the only water body in a hundred meters radio around it, a higher than usual density of frogs  resulted in a lauder sound. However, saturation in this track may be the result of a recording done too close to singing frogs using a parabolic microphone.  In this regard, in 3 occasions when citizens were played these recordings, sounds from points 1 and 2 were considered as “nice” but very noisy,  and that from point 5 as simply “very noisy”. However, point 5 is a recording inside a moving bus, a soundscape that we experience normally in our lives, and that doesn’t seem to irritate that much. In fact, Japanese people price silence inside a bus (not talking) even though this is already a very noisy ambient per se. On the other hand, at point 7 in the downtown of Sendai, on the 31st floor in AER building, a quiet environment where people talking were the dominant sound, the soundscape was still full of car sounds, despite the height at which it was recorded. In general, the 9 recordings in our study show a clear trend where  natural sounds are dominant in sites away from the urbanized areas. This seemingly obvious result is in fact an indicator that our modern lifestyle disconnect us form nature, where we create our own environment, with its own unnatural soundscape that ends up being the norma. We believe that in order for Environmental Education in the XXI century to change and generate new attitudes towards nature, this disconnection should disappear.Acknowledgment This study was supported by Grant-in-Aid for Young Scientists B (22730682).－ 71 －宮城教育大学 環境教育研究紀要　第 15 巻 (2013)ReferencesEchenique-Diaz L.M. and Saito C. (2010). Bioacoustics as a tool for Environmental Education. Research Bulletin of Environmental Education center, Miyagi University of Education, 12: 41- 48.Potvin D. , Par r is K.M. and Mulder R.A. (2010) . Geographically pervasive effects of urban noise on frequency and syllable rate of songs and calls in silvereyes (Zosterops lateralis). Proceeding of the Royal Society, Series B. DOI: 10.1098/rspb.2010.2296.Table 1: Recording points around Sendai City.Point Description1 Parking lot in Kawauchi campus, Tohoku University2 Park in front of Miyagi University of Education COOP3 Stream in the forest in Kadan4 Aoba no Mori (the forest of Aoba Hill)5 Inside a bus at Aoba Avenue6 In front of Sendai Station7 AER building’s observation deck, 31st floor8 Yoshinari 1 chome residential area9 Rice fields next to Saikachi Dam, NishikigaokaTable 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 sound 1 -39.2 dB Cicada*2 -17.4 dB Frogs*3 -30.6 dB Forest birds*4 -17.2 dB Helicopter pass5 -14.0 dB Bust stop announced on speakers6 -12.1 dB Car sounds 7 -30.9 dB People talking8 -11.5 dB Car pass9 - 32.5 dB Frogs*－ 72 －Urban vs. natural sounds in Sendai city : a comparative studyFigure 1. Sendai City on the northeast of Japan.Figure 2. Recording points around Sendai City.－ 73 －宮城教育大学 環境教育研究紀要　第 15 巻 (2013)Point 1 Point 2 Point 3Point 4 Point 5 Point 6Point 7 Point 8 Point 9Point 3 spectrogram (fragment) 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 (forest birds 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.

Urban vs. Natural Sounds in Sendai city : A Comparative Study

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Urban vs. Natural Sounds in Sendai city : A Comparative Study

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