SOUNDMAPPING APPROACHES IN A SMALL SUBURBAN STUDY AREA

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1 SOUNDMAPPING APPROACHES IN A SMALL SUBURBAN STUDY AREA Michael CIK 1 ; Manuel LIENHART 2 ; 1/2 Graz University of Technology, Austria ABSTRACT There is sufficient scientific evidence that noise exposure can induce severe non-auditory health effects such as hypertension, ischemic heart disease and stroke, besides annoyance, sleep disturbance and cognitive impairments. Currently, epidemiological studies use the A-weighted sound pressure level, because it is relatively easy to model larger areas, but human perception of noise exposure from the variety of traffic sources is not always well represented by this approach. On the other hand, the general use of psychoacoustic indicators is currently hampered by its lack of modeling larger areas. Therefore, further research in the field of the spatial distribution of psychoacoustic parameters is required to introduce indicators, closer related to the human perception of sound, available for epidemiologic studies. A first step into this direction is done within the project RA²MSES in Austria for rail noise. In a pilot study in Southern-Austria a small area analysis of the spatial distribution of the psychoacoustic indicator loudness is conducted and the findings are compared with the results obtained with sound pressure level (SPL). Different models were fitted to the measured data of various locations in the study area and sound maps created for all indicators. In a first step the result based on the psychoacoustic parameter loudness were presented. Keywords: railway noise, soundmapping approaches, psychoacoustics, small area I-INCE Classification of Subjects Number(s): INDRODUCTION The meaning of soundscape is in the last years continuously transformed and modified. The multiple use of this term refers to the large diversity of interpretations with respect to the content of the soundscape idea making it impossible to present a general acknowledged definition. Often, the institutional and disciplinary backgrounds of the researchers have a sustainable effect on their soundscape concept (1). Only a total appreciation of the acoustic environment can give us the resources for improving the orchestration of the world soundscape (2). A soundscape is not an objectively existing reality (you cannot fly above the soundscape and take a picture), but it is a culturally-affected environment constituted by human perception (3). Today, environmental noise is calculated and depicted in noise-maps with the A-weighted sound pressure level (SPL). Those noise maps, neglecting the specific character of a soundscape, are often the basis for discussions and interpretations regarding noise annoyance. In this context, it is necessary to reflect also the meaning of annoyance. Annoyance will be used here as an overall evaluation of disturbances and unpleasantness of environmental noise, a negative feeling evoked by sound. However, annoyance is sensitive to subjectivity, thus the social and cultural backgrounds have an important influence on the subjective attitudes of people to noise (4) and they must be considered besides physical parameters. Therefore, the complexity of noise annoyance and the description of soundscapes, which means more than only the determination of annoyance, cannot be simply described by a single parameter, because many factors contribute to it. Hence, individual, contextual or physical variables, causing a deviation from the law of averages implied by dose-response relationships, must be 1 michael.cik@tugraz.at 2 manuel.lienhart@tugraz.at 5731

2 determined with respect to an improved understanding of annoyance as caused by environmental noise (5). Psychoacoustics will make a meaningful contribution to it and will allow the detection of specific soundscape features. Psychoacoustics covers one important field of the different dimensions involved in the environmental noise evaluation process. It describes sound perception mechanisms in terms of several parameters, such as loudness, sharpness, roughness, and fluctuation strength as well as further hearing-related parameters. Soundscape is used as the complex superposition of natural, human and technical noises and their perception. Soundscapes consist of a number of spatially distributed sound sources, which give the soundscapes their distinctive features. The emitted noise of each source could be measured and analyzed in terms of several parameters. However, the annoyance due to given individual sound sources cannot be transferred to the overall annoyance of an entire, complex soundscape containing the noise of different sound sources, because of e.g. masking effects (6). Surveys have documented that spatiality plays an important role for physiological reactions and annoyance. In the context of industrial noises, a study has investigated the influence of the direction of sound incidence on physiological reactions and loudness evaluation. It could be observed that the reaction to the multi-directional situation was higher than the reaction to the uni-directional situation, although both noise situations produced the same SPL at the position of the listener (7). Therefore, the spatial distribution of sound sources as well as the direction and speed of any movement of these sources can be relevant for the perception and evaluation of environmental noise. In fact, the determination of noise annoyance caused by complex sound situations arising from the superposition of the emitted sounds by a number of sources is very complicated and the (binaural) signal processing involved in human hearing has to be considered. The use of aurally-accurate measurements provides the opportunity to consider binaural signal processing phenomena. The fact, that annoyance resulting from the listener s surrounding soundscape is also depending on the personal attitude of the listener, further increases the intricacy of the soundscape approach, which has to integrate important aspects, such as the physical situation, experience and interpretation of the environment into one broad concept (8). Even visual information of the location affects noise evaluation (9). Abe et al. concluded that the influence of visual and verbal information on the auditory evaluation of environmental sounds is considerable (10). In order to capture the mentioned difficulties with respect to human sensation and evaluation of environmental noise, the transformation of a sound event (the physical situation) into the perceived sound event has to be considered. This transformation is influenced by different aspects: first of all, the physical aspect; secondly, the psychoacoustic aspect: the human hearing processes sound depending on the time structure and frequency distribution. And thirdly, the psychological aspect, including context, the kind of information, the individual expectation and attitude to the sound, is finally leading to the evaluation of the sound event. Therefore, a multi-dimensional approach, considering these different aspects adequately, is necessary to meet the requirements of the soundscape approach, the total appreciation of the acoustic environment (2). This realistic and comprehensive overview was already published by Genuit et al. in 2006 (11) A first step into this direction is done within the project RA²MSES in Austria for rail noise (12). In a pilot study in Southern-Austria a small area analysis of the spatial distribution of the psychoacoustic indicator loudness is conducted and the findings are compared with the results obtained with sound pressure level (SPL). Different models were fitted to the measured data of various locations in the study area and sound maps created for all indicators. In a first step the result based on the psychoacoustic parameter loudness were presented. 2. METHODOLOGY 2.1 Case study Within the project RA²MSES a comprehensive case study on a railroad south of Vienna has been conducted. Binaural measuring equipment was installed on changing sites and additional interviews in the neighborhood have been made, in order to assess the subjective annoyance due to railroad noise. 5732

3 The study area has been selected based on its fulfilling of all topological and traffic-related characteristics: Sub-urban settlement Railroad is the major source of noise. Medium to high traffic volumes (mixed traffic). Homogenous housing characteristics (no towers etc.). No noise control measures at the infrastructure. Measurement positions on open field, but also sheltered from the wind to some extent. Figure 1: Measuring positions in the study area The selected study area is located in a small city named Neunkirchen (~12,500 inhabitants, Lower Austria) at one of the Austrian main rail lines (Figure 1). Train frequency is approximately 5 trains/hour (per track) during daytime at a maximum track speed of 150 km/h (mean 108 km/h). Most of the houses were built 50 years ago, single and double stories in typical suburban structures with gardens of 500 to 1500 m². The measurement positions are located at distances between 30 and 250 m to the track. Acoustic-measurement-setup of the case study A three-step approach was used to record the necessary data for the case study. As a first step, the binaural measurement equipment was installed on a free-field at section kilometer 63.4 of the railroad track ( Südbahn ) within the study area. At the test site the railroad runs on two ballasted tracks with concrete sleepers and UIC 60 rails. Two HSU (Head Shoulder Unit) III.2 (2 dummy heads by HEAD acoustics GmbH) were used to record binaural data within a free field situation. Of those two one was installed at a distance of 7.5 m and the other one was installed at a distance of 25 m to the middle of the rail track, both were setup to a height of 1.8 m above the top of the railhead. The first HSU remained at a distance of 7.5 m to the rail track throughout the day (8 hours). The second HSU positioned at a distance of 25 m was further moved to a distance of 50 m after a measuring period of 4 hours and remained at this position for another 4 hours. In a second step binaural recordings were performed using two HSU at 7 one-family homes in the study area for a measuring period of 4 hours per house. This was done for examining how railroad noise decreases is perceived with increasing distance. The 7 one-family homes were chosen in regard 5733

4 of their distance to the railroad track and should represent the soundscape experienced at the surrounding houses (Figure 1). At the one-family homes one HSU was placed outside at the rail track facing façade of the house and one HSU was set-up in the living room. After a first evaluation of the obtained data, it turned out, that rail noise is in terms of the psychoacoustic indicator loudness clearly distinguishable from other noise sources only up to a distance of about 100 m to the rail track. Therefore, in a third step, 3 (positioned at a distance of 30, 40 and 90 m of the rail track) out of the 7 measuring sites were selected for a further analysis. At those 3 measuring sites 2 HSU s were used. The first HSU (HSU1) was placed again at the rail track facing façade of the house and remained there for the entire measuring period of 4 hours, the second HSU (HSU2) was positioned at the opposite side of the house at 3 different locations, it remained at each location for about 1.5 hours. Those 3 locations are shown in Figure 2 and defined as followed: Position 1: HSU2 was positioned at a distance of 2 m to the façade at about the middle of the house Position 2: HSU2 was positioned at a distance of 2 m to the façade in 45 angle to the left corner of the house Position 3: HSU2 was positioned at a distance of 2 m to the façade in 45 angle to the right corner of the house Figure 2: Locations for measuring the acoustic shadowing effect of houses on Loudness Additionally, also the passing train types and abnormalities were noted during the binaural measurements, for further analysis. Subjective data acquisition neighborhood survey In addition to the on-site measurements, also the subjective annoyance due to railroad noise of the people living in the study area needed to be considered. Therefore, a questionnaire, which considers socio-demographic data, annoyance due to noise in general and annoyance due to railroad noise in particular was developed. The assessment of railroad noise induced discomfort was done using the International Commission on Biological Effects of Noise (ICBEN) 5-point verbal and 11-point numerical scale. This questionnaire was answered by people living directly at as well as by four people living around each measuring point. The interviews were carried out during the time frame in which the measurement at the corresponding measuring point was conducted. In total, 38 opinions from residents living in the Neunkirchen area were collected. 5734

5 2.2 Data evaluation Following the data acquisition, an evaluation scheme needed to be developed, in order to create an optimal data set for the development of a spatial distribution model for various psychoacoustic indicators afterwards. The data was in the first step analyzed on a per train and measurement locations basis, according to the additional records of passing trains. Those train passages (altogether about 370) were analyzed based on the latest standards of various acoustic and psychoacoustic parameters for different indicators using the software package ArtemiS SUITE V7 by HEAD acoustics GmbH. In the next step the results needed to be transformed into a numerical representation of the acoustic exposure at a specific point. The problem, which needed to be solved, were the different train types using that part of the railroad network in different quantities at each location. Those train types were ranging from regional commuter trains, long distance trains to freight trains, each represented by unique sound characteristics. The easiest way to overcome this problem was to calculate the mean value out of all median loudness values of each train passage on a specific location. This approach allowed to calculate approximated exposure levels at each considered measurement location. Nearly all measurements were taken into consideration for calculating exposure levels, apart from measurements at position 1, which were used for determining shadowing effects of loudness, and all indoor measurements. 3. DEVELOPMENT OF A SPATIAL DISTRIBUTION MODEL AND RESULTS In order to develop a spatial distribution model a parameter representing the noise emission of passing trains was needed. The nearest possible measurement distance was 7.5 m to the middle of the considered rail track. Therefore, the emission level from the rail track is represented by the exposure level at this distance. All distances from each measurement location are relating to this point. Table 1 shows the loudness exposure at the different measuring points in relation to the defined source of the railroad noise emissions. Table 1 Loudness exposure at different measuring points in relation to distance from the source Measuring Point Distance [m] Loudness exposure (median) [sonegf] MPFF7.5 0,00 77,74 MPFF25 17,50 50,71 MP1 20,30 53,69 MP1 Pos. 2 29,55 43,91 MP1 Pos. 3 32,07 61,92 MP2 32,50 43,85 MPFF50 42,50 36,51 MP2 Pos. 3 43,04 52,73 MP2 Pos. 2 47,08 41,47 MP3 54,30 34,88 MP4 86,40 13,12 MP5 87,12 15,17 MP4 Pos. 3 91,82 13,40 MP4 Pos. 2 97,18 14,78 Using this data base a regression analysis was performed, which suggested the best fit to an exponentially decreasing model in terms of distance, as Figure 3 illustrates. 5735

6 Loudness [sonegf] 100,00 Residual standard error: (12 DOF) 90,00 80,00 Adjusted R²: ,00 p-value: 5.737e-08 60,00 50,00 40,00 30,00 20,00 10,00 0,00 0,00 20,00 40,00 60,00 80,00 100,00 120,00 Distance [m] Figure 3 Loudness [sonegf] exposure at different measuring points and resulting exponential model This exponential model can now be used as an initial point for calculating roughly a spatial distribution map for the psychoacoustic factor loudness. However, it doesn t provide means for the calculation of shadowing effects of houses, which is rather difficult, when comparing data from HSU2 at position 1 with data from HSU1. It seems that the decrease of loudness, when facing an obstacle, is noticeable especially at shorter distances, but can increasingly be neglected with greater distances, when the soundscape is mixed with various sound sources, as Figure 4 shows. percentage of loudness exposure at HSU2 at position 1 compared to HSU1 [%] 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 0,00 20,00 40,00 60,00 80,00 100,00 Distance from the emission source [m] Figure 4 Percentage of loudness exposure left after facing an obstacle at various distances With those two models it is possible to create a soundmap (cf. 5) for the psychoacoustic factor loudness, in order to get a rough impression of the development over distance. 5736

7 Figure 5 Soundmap of the factor loudness based on the developed two models As comparison also the noisemap based on Sound pressure level LDEN (Level day-evening-night) was calculated (Figure 6). In the next step a detail analysis and investigation between the different maps is arranged. Figure 6 Noisemap based on Sound pressure level LDEN (Level day-evening-night) 5737

8 4. SUMMARY and OUTLOOK Currently, epidemiological studies use the A-weighted sound pressure level, because it is relatively easy to model larger areas, but human perception of noise exposure from the variety of traffic sources is not always well represented by this approach (13,14). On the other hand, the general use of psychoacoustic indicators is currently hampered by its lack of modeling larger areas. Therefore, further research in the field of the spatial distribution of psychoacoustic parameters is required to introduce indicators, closer related to the human perception of sound, available for epidemiologic studies. A first step into this direction is done within the project RA²MSES in Austria for rail noise. In a pilot study in Southern-Austria a small area analysis of the spatial distribution of the psychoacoustic indicator loudness is conducted and the findings are compared with the results obtained with sound pressure level (SPL). Different models were fitted to the measured data of various locations in the study area and sound maps created for all indicators. In a first step the result based on the psychoacoustic parameter loudness were presented. Results have shown the possibility to use our methodology for the description of psychoacoustic parameter, especially loudness, of the given hypotheses. Future steps will be oriented to detailed statistical analysis of the acoustic and psychoacoustic data. It will be combined with the discovery what the human feeling of pleasantness or annoyance depends on and how to use this knowledge in the design and renovation will need comparison of the measured acoustical data with sociological investigations. The main focus of the development of the spatial distribution model will investigate more measurement points around the house, different heights and developing a universal model for different landscapes and traffic noise sources. REFERENCES 1. Berglund B. Theory and method in perceptual evaluation of complex sound. In: Recent Trends in Hearing Research. H. Fastl, S. Kuwano, A. Schick (eds.). Oldenburg, BIS Verlag, Schafer R. M. The soundscape: our sonic environment and the tuning of the world. Destiny Books, Rochester, Lorenz A. M. Klangalltag Alltagsklang. Evaluation der Schweizer Klanglandschaft anhand einer Repräsentativbefragung bei der Bevölkerung. Zentralstelle der Studentenschaft, Zürich, Darui Z. Noise exposure. In: Recent Trends in Hearing Research. H. Fastl, S. Kuwano, A. Schick (eds.). Oldenburg, BIS Verlag, Taylor S. M. Noise annoyance research: purpose and progress. In: Recent Trends in Hearing Research. H. Fastl, S. Kuwano, A. Schick (eds.). Oldenburg, BIS Verlag, Guski R. Interference of activities and annoyance by noise from different sources. In: Contributions to psychological acoustics. Results of the 7th Oldenburg symposium on psychological acoustics. A. Schick, M. Klatte (eds.). BIS Verlag, Oldenburg, Genuit K., Blauert J., Bodden M., Jansen G., Schwarze G., Mellert V., Remmers H. Entwicklung einer Messtechnik zur physiologischen Bewertung von Lärmeinwirkungen unter Berücksichtigung der psychoakustischen Eigenschaften des menschlichen Gehörs. Schriftenreihe der Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, Forschung Fb 774, Wirtschaftsverlag NW, Werner, H. U. Soundscapes zwischen Klanglandschaften und Akustik Design. Welt auf tönernen füßen. die töne und das hören. Kunst- und Ausstellungshalle der Bundesrepublik Deutschland, Viollon, S. Two examples of audio-visual interactions in an urban context. Euro-Noise 2003, Naples, Italy, Abe K., Ozawa K., Suzuki Y., Sone T. Comparison of the effects of verbal versus visual information about sound sources on the perception of environmental sounds. Acta Acustica united with Acustica 92 (2006) Genuit K. and Fiebig A., Psychoacoustics and its Benefit for the Soundscape Approach, Acta Acustica united with Acustica 92 (6) (2006) 12. Cik, M, Lienhart, M, Biebl, F & Schönauer, R (2016), Rail Acoustic Annoyance Monitoring Sensor System. in Annual Meeting of Transportation Research Board. pp. 1-11, Annual Meeting of Transportation Research Board, Washington DC (USA), January. 13. Lercher, P., and Schulte-Fortkamp, B. (2013). Soundscape of European Cities and Landscapes 5738

9 Harmonising, in Kang, J., et al. (2013). Soundscape of European Cities and Landscapes. (First Edition, Oxford by Soundscape-COSTTD0804), p Schulte-Fortkamp, B., and Dubois, D. [guesteditor] (2006). Ed. Special Issue on Soundscapes - Recent advances in Soundscape research, ActaAcustica Vol. 92, no